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  1. La Soufriere Volcano in St Vincent has exploded into life causing havoc for those in St Vincent and even impacting the sunshine and beautiful beaches of Barbados. NPR Cookie Consent and Choices WWW.NPR.ORG Its last three explosions were in 1812, 1902 and 1979 The average annual CET for the ten years preceding each explosion was greater than for the ten years of and succeeding the explosion. I wonder if the comparison of annual CETs for 2021-2030 against 2011-2020 will make it four times in a row?
  2. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mount Karthala Reason for Interest This is a very active volcano with a history of collapse, lava flows reaching the sea, going through a step change in activity in a tectonic environment that can create new large volcanoes. For me this is a very dangerous volcano which will cause issues in the near future. The Setting Named after the Arabic word for moon the Comoros Islands are volcanic islands between the coast of Mozambique and the island of Madagascar consisting of four islands – Ngazidja (Grande Comore), Moheli, Anjouan and Mayotte. Originally the Comoros were known as the ‘Perfume Islands’ due to their fragrant flowers, like the yellow ylang-ylang, used in perfumes which where imported and cultivated by French colonialists. While Mayotte remains under French Administration the rest of the islands became an independent nation in 1975. Grande Comore is the largest of the Comoros Islands with the capital city (Moroni) of the nation located there. The whole western side of Grande Comore is full of very highly rated beaches with Ndroudé being the longest and widest and Mitsamiouli Beach being considered one of the top beaches in the world. In the far northern part of the island is the small crater lake 'Lac Sale' which the locals call the bottomless lake probably due to some professional divers who tried to explore the lake but never came back. South of Moroni is Iconi which was once the capital of the Sultanate of Bambao and the first capital of Comoros. Moroni has a distinctly relaxed Arabian pace of life with the labyrinthine medina at the center which is crisscrossed by cobbled alleyways that are lined with intricately carved doorways, ornate mosques and charming Middle Eastern-style cafes. Moroni’s principal landmark is the two-storied and gleaming white 15th-century Old Friday mosque ( Nouvelle Mosquee de Vendredi Mosque dating back to around 1427) restored in the 1920s by France to pay tribute to those Comorians killed fighting for them during the First World War. The islands have a tropical climate with two clearly marked seasons: a cooler, dry period between May and October and a warmer, humid season between November and April. In November the summer monsoon (kashkazi) brings the highest afternoon temperatures—about 33 °C. The highest monthly rainfall occurs in January with about 11–15 inches. Dry season daily maximum temperatures fall to their lowest 29 °C in July. The average annual rainfall varies between 40 to 100 inches being highest on the windward northeast sides of the islands. The island has a coastal zone of mangroves followed inland by a zone of coconut palms, mangoes, and bananas up to about 1,300 feet. Above this a forest zone of Mohogany and orchids rises to about 5,900 feet where they give way to broom, heather, and lichens. Additional aromatic plants such as frangipani (Plumeria), jasmine, and lemongrass lend a delightful fragrance to the islands. The Tectonic environment The Comoros islands are roughly W-NW aligned and extend over 270 km in the Western Indian Ocean, on the northern edge of the Mozambique channel. The channel formed by the opening of the Somali and Mozambique Basins which dislocated the micro continent Madagascar to the south, away from the African continental plate. It was thought that a hotspot migrated under the chain of islands propagating to the northwest creating the volcanic Islands. This chain of volcanic islands and seamounts becomes progressively older from the still-active volcanism at Grande Comoros toward the older volcanic areas in northern Madagascar. Volcanic activity history and aging are not really consistent with a migrating hotspot as older volcanoes don't seem to be becoming less active. It is now proposed that East Africa consists of smaller sub plates and it is the twisting between these sub plates that has given rise to the islands. The clockwise rotation of Somalia relative to Lwandle creates a right-lateral shear zone which causes ripping and rifting along the sub plate boundary where the Comoros Islands are. A zone of broad deformation extends from the eastern boundary of the Rovuma microplate, across the Comoros Islands, and including parts of central and northern Madagascar. This does not explain volcanic rock analysis from the islands which still suggest a deep mantle source for Magma, so we might expect some refinement of tectonics in the area over time. 2018 Earthquake Mystery On 10 May 2018, an unprecedented long and intense seismic crisis started offshore, east of Mayotte, the easternmost of the Comoros volcanic islands. The population felt hundreds of events. Seismic activity began with a swarm of thousands of seemingly tectonic earthquakes then changed around June to a completely new form of earthquake signal which was so strong that it could be recorded up to a thousand kilometers away. These 20 to 30 minute long signals are characterized by particularly harmonic, low frequencies, similar to a large bell or a double bass, and are called Very Long Period (VLP) signals. French researchers have now identified the source of the puzzling activity as the birth of a submarine volcano some 31 miles off Mayotte's eastern shore. Sitting about two miles underwater, the new volcano stretches nearly half a mile high and extends up to three miles across. The Volcano Mount Karthala is an active volcano and the highest point of the Comoros Nation at 2,361 m above sea level. It is the southernmost and larger of the two shield volcanoes forming Grande Comore island (the other volcano being La Grille volcano). The Karthala volcano is very active, having erupted more than 20 times since the 19th century and is considered the youngest volcano in the island group. Frequent eruptions have shaped the volcano's summit caldera with two well developed rift zones intersecting at the summit caldera complex. Mount Karthala features eight or more overlapping calderas, nested pit craters and several terraces which are aligned in a sort of diamond shape. The center of the caldera complex is occupied by the crater “Choungou Chahalé”, the older main crater, which consists now of two inner pits. Another crater is “Choungou Changouméni”, a small circular pit crater of 220 m diameter in the northern lobe of the caldera, next to a small scoria cone from 1972. Around my inner crater, fumaroles emit superheated steam with a sulphurous odour. Elongated rift zones extend to the NNW and SE from the summit. The lower SE rift zone forms the Massif du Badjini, a peninsula at the SE tip of the island. A sharp landslide scarps constitutes the northern limit of the Badjini massif at the SE end of Grande Comore. This landslide scarp is evidence of a large failure of the E flank of Mt. Karthala. Past Eruptions Two strong eruptions in 1972 and 1977 did significant damage as lava flows reached the ocean. In 1977, the coastal village of Singani was partly destroyed by lava flows. In 1860, a lava flow even reached the coast close to the island capital where you will find a number of lava tubes. The 1991 eruption marks the beginning of a style change in Karthala’s behaviour. The eruption followed three months of increasing seismicity and inflation. After several hours of relative calm a sizeable phreatic explosion further enlarged Choungou Chahalé and lowered its floor. In a visit to the summit two weeks after the 11 July explosion people heard a “fountaining” sound, but no lava fountains or any other source were visible. It turned out later that this would have been the sound of the forceful arrival of water into the new crater, forming a crater lake for the first time. Scientists believe now, that this explosion had changed the hydrothermal system below the volcano, as all following eruptions were phreato-magmatic in nature. Recent Activity 2005 eruption During April inhabitants heard a rumbling coming from the volcano and observed an ash column above the summit. The first ash-fall deposits began to form soon afterwards on the island's eastern side. According to the firsts reports, ash deposition increased and continued accompanied by a strong smell of sulfur. Observers saw a very dark plume spreading into a mushroom shape and accompanied by lightning flashes. Some inhabitants panicked and fled the island's eastern villages. During the next few days ash continued to fall on the eastern part of the island and were heavy enough to require inhabitants to use umbrellas to get about. A pilot for Comoros Aviation, flew over the west flank and observed a large plume in the direction of the Chahalé crater and observed airborne molten ejecta. As the eruption continued authorities decided to evacuate some 30,000 residents from eastern villages. The following days saw ash falls on the island's western and northern parts, notably, on the country's capital city of Moroni and on the Hahaya airport. Lahars damaged roads and hundreds of houses, affecting thousands of inhabitants at the foot of Karthala volcano. Eruptions continued through to later in the year when investigators ascended Karthala and observed a molten-surfaced lava lake inside Chahalé crater. 2006 activity The eruption started during June with the first signs being smoke from the volcano. Rather than being explosive with ash emissions this eruption was more effusive with lave flowing down the side of the mountain. Within a few days the eruption stopped and lava flow stopped before it could reach coastal areas. 2007 Activity Scientists from the KVO reported that an eruption occurred during the evening of 12 January. A local news article noted Moroni residents observing jets of red flames above the summit. An ash plume was observed above the volcano and Aerial observations later in the month showed a lava lake forming within the crater. 2012 Activity Observers in the villages of Mde and Mkazi, on the W flank of Karthala, reported increased incandescence from the summit during the night of 9-10 May. Discussion It is certainly a dangerous volcano, but what perhaps catches my attention is the risk of Lahars and Landslides. Maybe it is just the hotspot contention or the mysterious new volcano created under water near Mayotte. Certainly worth a bit more investigation and conversation.
  3. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing The Salton Sea Buttes Volcanoes Reason for Interest Volcano activity in Southern California tends to escape attention due to the priority concerns with earthquakes. With volcanic activity in the Salton Sea area being younger than originally thought and crustal extension (rifting) being held back by the locked San Andreas Fault the area needs monitoring. The volume of melt material below the area is thought to be very large so we should not assume that future volcanic activity in the area would be quite as benign as it has been till now. This is probably why the USGS now consider this area to be of particular concern. Maybe what really piques my interest is seeing a side to California you don't normally see. The Setting One of the world's largest inland seas and lowest spots on earth at -227 below sea level, Salton Sea was re-created in 1905 when high spring flooding on the Colorado River crashed the canal gates leading into the developing Imperial Valley. For the next 18 months the entire volume of the Colorado River rushed downward into the Salton Trough. By the time engineers were finally able to stop the breaching water in 1907, the Salton Sea had been born at 45 miles long and 20 miles wide and 51 feet deep. In the 1950’s the Salton Sea was the place to vacation for Hollywood stars. The Hollywood influx quickly turned this small vacation getaway into an attraction drawing in 500,000 people a year. Star-filled clubs such as Ace & Spades and the 500 Club sprouted up and recreational boating took off. Many celebrities would come from Los Angeles and down from Palm Springs to take part in the beach life and great water sports offered at Salton Sea. Increasing salinity in the Salton Sea basin has limited the number of types of fish that can be found there, and most fish currently caught are Tilapia. The once-bustling hotels are derelict, broken wooden frames of buildings stand in some spots as other structures are badly decaying with graffiti spray painted over the boarded-up windows and doors. On hot summer days when the temperature can reach up to 120F (48.8C), a pungent Sulphur odor hangs in the air that can be smelled 150 miles away in Los Angeles. Near the Salton Sea can be found Salvation Mountain which Leonard Knight used 30 years of his life and gave up everything to build this colorful masterpiece. In 1984, Leonard was set out to spread the word of the bible and when his truck broke down he starting building Salvation Mountain on the very spot and lived onsite until 2012 when he was moved to a nursing home. Nearby can be found East Jesus a community of artists that live together, create art and party in the desert. The imperial sand dunes to the south of the sea are a 15 mile long and 3 mile wide stretch of 400 foot tall sand dunes. The Dunes have been the home to the tapping of many movies including Stars Wars and is a huge haven for dune buggy enthusiasts. The Date Farms are the most important part of the Salton Sea area’s economy today. Ever since the celebrities and tourists stopped coming in the 1960’s most of the area has become a rundown, dingy area, but the Date Farms have stayed strong. To the North of the Sea is Palm Springs which is like a mini desert Hollywood. Well it’s not quite filled with the high level of stars it was in the 50’s when the Salton Sea was booming but it is still a beautiful place to visit. If you’ve ever wondered what Jurassic-sized palm trees may have looked like then the Anza-Borrego State Park and Palm Canyon is your chance to see. This grove of 100 foot tall bushy palms is crazy. The park is located to the west of the Salton Sea. Joshua Tree National Park is in southeastern California, east of Los Angeles and near Palm Springs and north of the Salton sea it is named after the Joshua trees native to the Mojave Desert. Between San Diego and the Salton sea is the Anza-Borrego Desert State Park. The Tectonic environment The Salton Sea is a large shallow lake located in the central Salton Trough of Southern California. The lake covers the southernmost extension of the San Andreas Fault (SSAF), where the fault takes a southwestward step to the Imperial Fault (IF). The region around the SSAF is actively being stretched due to extensional deformation. Numerous faults, high levels of seismicity and a series of young volcanic buttes suggest this region may be a source for future geohazards. The Salton Trough is an on shore analog to those rift systems in the Gulf of California. It includes the Coachella Valley, Salton Sea, Imperial Valley, and Mexicali Valley from northwest to southeast. The northern Imperial Valley and southern Salton Sea are seismically highly active. Seismicity occurs at 3–8 km depth in the Salton Sea geothermal field at the southeastern shore of the Salton Sea, 3–11 km depth in most of the Brawley Seismic Zone. The entire valley is also characterized by very high heat flow. Brawley Seismic Zone The Brawley Seismic Zone is a north-striking zone of northwest and northeast-striking faults that extends from the southern end of the San Andreas fault to the northern end of the Imperial fault. Across this zone crustal spreading occurs within the transition from the Gulf of California mid-ocean ridge to the San Andreas transform fault. The largest earthquakes to have occurred on the cross-faults were the magnitude 6.2 Elmore Ranch event in 1987. Although the Brawley Seismic Zone activity is clearly proximal to the southern San Andreas fault, the San Jacinto fault zone, and the Imperial fault, the current activity is remaining more than 10 km distant from any of these major faults. Repeated swarms occur in the Seismic zone as rifting occurs but there is no suggestion that these swarms are volcanic in nature. Three times in the last 15 years in 2001, 2009, and 2016, clusters of small earthquakes occurred within a few kilometers distance of the southern terminus of the SAF, within the northern Brawley Seismic Zone at a depth of 3 - 10km. There has been some concern that stress releases in the Brawley Seismic zone could trigger larger earthquakes on the San Andreas fault. The relative likelihood of such an occurrence was considered to be high because the southern SAF ruptured last in a major earthquake more than 320 years ago and the average recurrence rate of large earth-quakes on the southern San Andreas fault is about 180 years. Recent research however suggests that there is likely very little transfer of stress from the Brawley Seismic Zone and to the San Andreas fault. There is however very little research on the impacts to the Brawley Seismic Zone as a result of a significant San Andreas fault earthquake and we are left to guess whether this would lead to enough extension for volcanic activity to initiate again. The Volcano The Salton Buttes are a group of volcanoes in California in the south eastern part of the Salton Sea. They consist of a 7 kilometer long row of five lava domes each no more than 1 kilometer wide. From North to south they are Mullet Island, North Red Hill, South Red Hill, Rock Hill and Obsidian Butte. Obsidian Butte is surrounded by a lava flow, and Mullet Island has a characteristic "onion-skin" foliation with hot springs. The domes were formed by effusive eruptions, but at least Obsidian Butte and South Red Hill also experienced explosive eruptions, which at Obsidian Butte preceded the effusive eruption stage. The lava source for the volcanoes is a magma chamber beneath the Salton Sea, which also heats water for a nearby geothermal plant. These volcanic domes are associated with a local northeast-striking magnetic high that is interpreted to be caused by a magnetic mass, 30 km long, 3 to 12 km wide, and about 4 km thick, with its top buried more than 2 km below the surface. The intrusion under the Salton Sea is thought to be a pluton, an arm or protrusion from a deeply buried molten magma. This intrusion is parallel to the axis of the Salton Trough. Geophysical evidence shows that liquid magma is still present underneath the Salton Buttes. The buttes last erupted between 940 and not 30,000 years ago as previously thought with the U.S. Geological Survey listing the area as a high threat for future blasts. Hot Springs The Hot springs within Salton sea area were known and used by Indians for centuries. The first commercial development in the area dates from the turn of the century, when a therapeutic spa was opened in the foothills of the Chocolate Mountains near Bombay Beach on the east shore of the Salton Sea. This spring is still in use, and is unusual for its high water temperature, ranging from 135 to 180 degrees Fahrenheit. The hot springs are concentrated in a linear pattern along the eastern side of the valley. The line of springs extends from Desert Hot Springs into Mexico, and the arrangement strongly suggests that the warm waters are reaching the surface using fractures of the San Andreas fault system as conduits. There are several experimental geothermal developments in the Imperial Valley, extending from the south shore of the Salton Sea into Mexico. The Salton Sea geothermal field is the largest and the hottest of the several fields in the Salton Valley, and has the longest history of development. The mysterious mud spring Refusing to stay in place, a roiling mass of carbon dioxide and slurry-like soil is migrating across the state at a pace of 20 feet a year. Scientists currently have no real idea why it’s moving or if it can be stopped. Currently located just north of Niland, the mud spring is moving toward Union Pacific Railroad tracks and giving engineers there a headache. A well dug to depressurize the source of the gas had no effect. Steel walls driven 80 feet into the ground were also nonchalantly circumvented; the mud pot simply ducked under them and continued its freakishly linear path of destruction. Mud pots and mud volcanoes generally don’t emit much water, but this one is extremely vigorous, producing somewhere around 40,000 gallons of water a day. This mud spring is close to—but not on—the Wister Fault, a southeastern extension of the San Andreas. However, it appears to be tracing a path that’s at right angles to the region’s major faults. Recent Activity In late August 2005, a swarm of more than a thousand earthquakes between magnitudes 1 and 5.1 occurred at the Obsidian Buttes, near the southern San Andreas Fault. The earthquake swarm shook the nearby town of Brawley with the USGS attributing the temblors to faults in the Brawley Seismic Zone. In September, a sulfurous stench emanated from the Salton Sea and wafted across the Inland Empire. The odor was tentatively linked to a fish die-off, but could also have been caused by volcanic gases. Discussion These are not impressive volcanoes nor is this a glamorous part of California but for me that is exactly why it should be brought to peoples attention. Perhaps the biggest risk here is from earthquakes but there may well be a large source of Magma which would make me nervous.
  4. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mount Kaimon (Kaimondake) Reason for Interest A volcano less than 4000 years old with a typical repose time of 400 years which has not erupted for 1000 years suggests a volcano that needs close watching. At the base of the volcano is the Ibusuki City with a population of nearly 50,000 makes it worthy of attention. The Setting Kyushu is the third largest island of Japan's five main islands and the most southerly of the four largest islands. The Satsuma Peninsula is a peninsula which projects south from the southwest part of Kyushu Island. To the west lies the East China Sea, while to the east it faces the Osumi Peninsula across Kagoshima Bay. Near the southern tip of the Peninsula is the 924-metre-high mount Kaimon and the hot springs of Ibusuki Onsen The submerged 15 x 25 km Ata caldera under Kagoshima Bay is one of several large calderas in southern Kyushu. The Ata Caldera forms the bottom section of Kagoshima Bay and also the SE tip of Satsuma Peninsula. Within the perimeter of Ata Caldera are numerous more recent volcanic features including Mount Kaimon in the western corner of the caldera which covered the entire peninsula in scoria about 4000 years ago. About 5000 years ago, the 4x3km Ikeda Caldera was formed in the NW corner of Ata Caldera by a powerful explosive eruption. Lake Ikeda is the biggest volcanic lake in Kyushu with a circumference of 15km. The lake itself has a depth of over 200m and is also home to a unique species of giant eel which can grow up to 2m long and weigh up to 5kg. These eels are perhaps the inspiration for the legend of Isshii, the monster of the lake. Ibusuki at the southern tip of Kagoshima is famous for its sunamushi, or sand bathing. Volcanic hot springs line the coast of Ibusuki near to Mount Kaimon, warming the sands to 50-55 degrees Celsius. To experience a sand bath, you wear a light cotton yukata, and lie a shallow depression in the beach. An attendant will protect your face with a towel and shovel the warm sand over you until you’re buried up to your neck in the black sand, with only your head exposed to the air. After ten minutes or so, you emerge, warm and relaxed. The Flower Park Kagoshima is located near the southern tip of the Satsuma Peninsula, about a kilometer north of Cape Nagasakibana and below Mount Kaimon. The Flower Park claims to be the largest flower theme park in Japan with about half a million plants of more than 2400 different varieties. In addition to typical local flowers, there are other species from tropical regions all over the world, including Brazil, Australia and South Africa. The Kaimon golf course lies at the foot of the Mount Kaimon volcano at the southernmost point of Satsuma peninsula and utilizes natural geographical features. The course is noted for 'Kaimon Oroshi', the gust of wind blowing down the Kaimon Mountain and 'Umikaze', the sea wind blowing up from the ocean making a relatively difficult course to play. A big sand-craft event is held every spring on Fukiagehama Beach, one of the three largest sand dunes of Japan. Many teams from home and abroad participate to create original works. The Tectonic environment The Kagoshima rift is located in southern Kyushu Japan and includes Kagoshima Bay. Flora and fauna is representative of subtropical oceanic areas. The rift system developed behind the volcanic front of the Ryuku Arc and is about 30km wide. The southern part extends through Kagoshima Bay and accommodates five major calderas. About 1 million years ago crustal stresses changed from compression to extension. Crustal faults produced by the rapid crustal extension combined with melt from the subducted Phillipine Sea Plate have allowed large amounts of Magma to rise. This has lead to the formation of the Kakuto ,Aira ,Norrthern Ata ,Southern Ata and Kikai calderas. Northern Ata caldera is 16 km by 12 km in dimension and is located 200 m below sea level. This caldera is presumed to have formed 110 ka by an explosive eruption. Southern Ata caldera is 24 km by 14 km in dimension and is presumed to have formed 240 ka by explosive eruption. Subsequent eruptions occurred along the northwestern area of the presumed caldera. These included formation of the Ibusuki volcano about 30 ka, the Ikedako caldera and Kaimondake volcano. The Volcano Kaimondake (Mount Kaimon) is nicknamed the “Fuji of Kyushu” for its similarity in shape and symmetry to Japan’s most famous peak, although it’s just a quarter of its size standing at 934 m (3031, ft). Located at the southernmost tip of Satsuma Peninsula it is small stratovolcano. The summit crater, which is named Hachikubo, had been thought to be a collapse crater, but it was geologically proved to be a large explosion crater which was successively enlarged during an eruption. A mountain path spirals up from the foot of the mountain, such that you can enjoy the scenery from a variety of angles. At the foot is the oldest herb farm in Japan, Kaimon Sanroku Koen Ryoen. Here, you can enjoy cooking using herbs from the farm. At the foot of Mount Kaimon, there are two tunnels feared as the spookiest spots in Kagoshima Prefecture. There is no lighting system in the tunnels except for the holes in the ceiling at intervals to let through natural light. They are not one-way but crossing paths is extremely difficult as the roads are too narrow. The atmosphere is ominous and sinister even in daytime. A large number of spooky phenomenon have been reported by the drivers : the backseat of the car suddenly got wet; some face-like figure stuck out from the ventilation hole; a man in a military uniform was walking with blood splatters all over his body. If you happen to look at a female face dangling from a ceiling hole, there will be a little chance that you can safely go out of the tunnels. Past Eruptions Eruptive activity began at Kaimondake approximately 4,400 years ago with an initial eruption in a shallow sea area. Eruptions occurred repeatedly, emitting lava, and it is postulated that approximately 2,500 years ago a volcanic edifice roughly the same size as the present one had been formed. Significant amounts of volcanic material were discharged in the volcanic activity approximately 1,500 and 2,000 years ago, greatly contributing to the formation of the stratovolcano. After this, during the historical era, the eruptions in 874 and 885 greatly changed the topography of the summit area, and towards the end of the eruptions, a lava dome was formed inside the crater. Kaimondake last erupted in the Heian period about 1,150 years ago. The eruptions of the Heian period occurred in year 16 of the Jogan era (874 AD) and the first year of Nin-na era (885 AD). The houses and farmland of the Hashimuregawa and the Shikiryo archaeological sites located in Ibusuki city were significantly damaged by the eruption of Kaimondake volcano. Discussion Perhaps it is the shape or the haunted tunnels that caught my attention. More likely it is that this is young volcano that has been eerily quiet in a quieter part of Japan that concerns me.
  5. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing The Robinson Crusoe Island Tsunami Reason for Interest I had never heard of the Juan Fernández Islands or Robinson Crusoe Island but the accounts of the tsunami were so vivid that I thought it was important to remind us that lives can be devastated by disaster. Throw in a little mythical history and I find it fascinating. The Island Robinson Crusoe Island is the second largest of the Juan Fernández Islands, situated 670 km west of San Antonio Chile. It is the most populated of the islands with most living in the town of San Juan Bautista at Cumberland Bay on the north coast. From 1704 to 1709, the island was home to the marooned sailor Alexander Selkirk, who at least partially inspired novelist Daniel Defoe's fictional Robinson Crusoe in his 1719 novel. Robinson Crusoe Island lies to the west of the boundary between the Nazca Plate and the South American Plate. A volcanic eruption on the island was reported in 1743 from El Yunque, but this event is unconfirmed. The Fuerte Santa Barbara fort once used by 18th century Spanish to protect themselves from raucous pirates. The islands have a subtropical Mediterranean climate moderated by the cold Humboldt Current, which flows northward to the east of the islands, and the southeast trade winds. Temperatures range from 10 °C to 22 °C. In 1977 the archipelago was named a biosphere reserve and now forms part of the enormous Juan Fernandez Marine Park. A particular success has been the South American fur seal, a species that was almost extinct 40 years ago, which now has a population of 30,000 on the islands. Just offshore in the harbour can be found the wreck of the German light cruiser SMS Dresden. Having escaped the battle of the Falklands she eluded her British pursuers until she put into Robinson Crusoe Island in March 1915. Her engines were worn out and she had almost no coal left for her boilers. After The British violated Chilean neutrality and opened fire on the ship the Germans scuttled the Dresden and the majority of the crew escaped. The Tectonic environment The west coast of South America is a subduction zone where the Nazca Plate is plowing under the South America Plate at an average rate of 3 inches per year. The boundary where the two plates converge is marked by a trench located about 62 miles offshore where the Nazca Plate begins its descent beneath the South America Plate. When plates become locked together for a time and earthquake may occur as the plates lurch past each other violently. If this occurs at a subduction zone then crust one side of the earthquake will drop and on the other rise and it is this movement that causes a tsunami. A First hand Account British couple Rhian Salmon and Andy Whittaker embarked on the trip of a lifetime in their yacht. Their first port of call was the volcanic paradise of Robinson Crusoe Island where they moored near to the village of San Juan Bautista. The island is part of the Juan Fernández Islands 400 miles off the South American coast. In the early hours of 27 February, the day they were due to set sail again, a devastating earthquake struck Chile, and unleashed a massive tsunami westwards across the Pacific directly towards the island. At 4am they work up to the sound of water rushing under the boat. Then they heard an almighty roar resonating around the bay. Water is flying past the yacht in big whirls, carrying trees and what looks like roofs. The water sweeps back towards the open ocean carrying with it all objects in its path. They hear cries and calls from people on the roofs and trapped in the houses which fly past them. Andy reaches over the side and pulls a boy on to the deck shivering, covered in oil and cuts, looking for his family. They are surrounded by strong fuel fumes and there is a strong noise of gas hissing from gas bottles that have been ripped from the houses they used to supply. Another older boy climbs on board. There are other boats in the water now and a Navy boat. The Navy boat is unoccupied and dragging hard on its mooring. Andy and the two boys fend of the boat off while on the other side a rooftop is pushing up against us, and next to it a whole house. Further away, a family are stranded on the top floor of a floating house. They see the yacht and start to swim. Andy throws a rope to them and they grab on. Andy pulls up a young girl but the other three are swept away. As dawn approaches they start to see the damage. The whole town front has been wiped out, the navy boat is wrecked on the rocks, the shops where they bought supplies is gone, as are the school and town square. The Maule Chile Earthquake The 2010 Chile Maule earthquake occurred off the coast of central Chile on a Saturday in the early hours of the morning. The magnitude of the earthquake was recorded as 8.8 on the moment magnitude scale, with intense shaking lasting for nearly four minutes. Since the earthquake was in the middle of the night on a weekend injury due to falling damaged infrastructure like bridges and roads was minimized. The tsunami waves that followed this event affected the coastal regions between the cities of Valparaiso and Valdivia, with minor effects as far as Coquimbo. In Chile 525 people lost their lives, 25 people went missing and about 9% of the population in the affected regions lost their homes. The focus of the earthquake occurred at a depth of about 22 miles below the surface of the Pacific Ocean. The earthquake—resulting from the rupture of a 300- to 375-mile stretch of the fault that separates the South American Plate from the subducting Nazca Plate. Stress brought on by the convergence of the two tectonic plates caused rocks to shatter along the boundary between them. This forced a portion of the seabed upward, displacing the water above and triggering a tsunami. The Chilean town of Constitución was inundated by waves as high as 50 feet and the port of Talcahuano was damaged by a wave measuring nearly 8 feet high. Traveling across the Pacific Ocean at nearly 450 miles per hour the tsunami encountered the Robinson Crusoe Island approximately 420 miles off the coast of Chile. The tremor shook the capital Santiago for a minute bringing down telephone and power lines. Santiago's international airport was forced to close, a highway bridge collapsed and rubble from damaged buildings fell on to the streets. The largest earthquake ever recorded struck the same area of Chile on 22 May 1960. The magnitude 9.5 quake killed 1,655 people and left 2 million homeless, and caused a tsunami that killed people in Hawaii, Japan and the Philippines. Several factors contributed overall to the low casualty rate and rapid recovery. A major factor was the strong building code in Chile and its comprehensive enforcement. A second factor was the limited number of fires after the earthquake due to the shut down of the electricity grid early in the earthquake. Third factor was the practiced close coordination between emergency management teams. Discussion While an earthquake of the same magnitude in the same area is unlikely there will be other earthquakes along the fault line in the future. History suggests the next one could be even bigger and reach right across the Pacific ocean.
  6. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Kawah Ijen Reason for Interest Kawah Ijen is a volcano made famous by it Blue flames and is obviously a volcano with some unrest, but what piques my interest is the reports from the 1817 eruption. There just seems to be some something about it that is still an puzzling. The Setting East Java borders with Central Java to the west, while the narrow Bali Strait to the east separates Java from Bali. Located in eastern Java is also the island of Madura, which is connected to Java by the longest bridge in Indonesia, the Suramadu Bridge. East Java is known for its coastal scenery including Plengkung Beach which reputedly one of the best beaches for surfing. East Java has a tropical monsoon and savanna climate at lower elevation and subtropical at higher elevation. Compared with the western part of Java Island, East Java in general has less rainfall. The average temperature ranges between 19-34 °C. The Tectonic environment The Ijen Caldera Complex is located in eastern Java along the volcanic front of the Sunda arc. The mixed Sunda arc is related to the subduction of the Indo-Australian plate beneath the Eurasian plate along the 1200 km long Java trench. The top of the subducting plate lies 180 km below Kawah Ijen, has an approximate age of 130 Ma at the trench and dips at an angle of 42 Degrees. Convergence of the Australian plate at 7 cm per year is nearly orthogonal near Kawah Ijen. The Volcano The Ijen volcano complex is a group of composite volcanoes in the East of Java. The complex is inside an large caldera Ijen (Kendeng Caldera) which is about 20 kilometers wide. Many other post caldera cones and craters are located within the caldera or especially along its rim. The Gunung Merapi stratovolcano is the highest point of that complex sitting on the caldera rim. Just to the west of Gunung Merapi within the Caldera is Kawah Ijen with and active crater 722 meters wide and 200 meters deep. Within the crater is a lake which is recognized as the largest highly acidic crater lake in the world. The lake has a turquoise blue colour due to the high concentration of minerals within the water. It is also a source for the river Banyupahit which has a significant detrimental effect on the downstream river ecosystem. There is an active solfatara that emits hot sulfurous gases which ignite as they emerge burning with an electric blue flame. The flames are difficult to see during the day but illuminate the landscape at night. Often the temperature is low enough that the sulfur condenses, falls to the ground as a liquid and solidifies. This produces a renewable deposit of mineral sulfur that local people mine. Kawah Ijen’s has erupted both high-Ca and low-Ca magmas which indicates that Kawah Ijen is tapping both the rim-volcano reservoir and intra caldera reservoir. There is no evidence for physical mixing and mingling implying separate magma pathways for magmas erupted from these different reservoirs. Kawah Ijen Sulphur Mines The kawah Ijen Sulphur mines are located down in the crater. Every morning two hundreds miners climb down to the bottom of the crater for the next load of Sulphur. Volcanic gas which escape from fumaroles at the bottom of the crater are directed through the huge ceramic pipes. As the gas cools and condenses in the pipes the gas turns into the liquid Sulphur. This red liquid Sulphur flows out from the pipes to the ground and becomes hard and yellow immediately. The miners then chop lumps of yellow Sulphur off and fill their baskets with Sulphur and then carry the heavy load up out of the crater. Down in the crater the miners dodge clouds of poisonous Sulphur dioxide and hydrogen Sulphide without any mask. Miners carry up to 100 kilograms of Sulphur in baskets connected by yoke 300 meters from the bottom of the crater to the crater rim. He then goes another kilometer down slope to the weighing station before going another two kilometers through the jungle to the collecting point at Pos Paltuding. Attempts in the past to use mules to do the carrying failed as they were not able to cope with the conditions. Rivers The Kawah Ijen crater lake is one of the world’s largest pools of hyper acidic volcanic water. In 1921 a dam was built on the western crater belt to control the water level in the lake and to regulate the outflow of hyper acidic water in the downstream area,. For several decades the dam’s sluices have not been used as the water level remained below the dam lip. However water from the lake leaks through the rock basement at several points below the dam in to the Banyupahit river. The lake is kept intact by the dam that has been reinforced due to structural weakness but remains vulnerable to even a small volcanic events and earthquakes. The river is diluted mainly by two tributaries within the wider Ijen caldera near the village of Blawan and flows down a 50 m high waterfall at the wider caldera rim. After leaving the Ijen caldera, the Banyuputih river flows through the largest single expanse of forest on Java which is part of the Ijen Malang Raung nature reserve. Despite dilution at no point does the Banyupahit river meet water quality standards. The chemistry of the river water seemed to have changed over the past decade and the negative effect in the irrigation area increased. Any increase in activity would have serious consequences on water quality over a wide area. Past Eruptions In 1817 the crater was reported has having fumaroles and a depth of 18m with no lake. The same year the volcano entered an eruptive phase with a 250m deep crater being formed as a result. Eye witness accounts reported ash was dense enough to turn day into night and to make trees and bamboo huts collapse under the weight. At the same time, cold mudflows laden with debris came down the outer flanks of the volcano, following the Banyu Putih valley north and flooding the Asambagus plain, and southeast to Banyuwangi flooding the plains south of it and destroying a complete forest in the process. The impact of the eruption on easternmost Java was severe as large areas of fertile low-lying farmland around Banyuwangi and in the Asambagus plain were covered in sulfur-bearing mud, which hardened into a solid crust, making them unusable for agriculture for several years. By 1820 the lake had formed in the new crater. In 1952 there were phreatic eruptions when an ash and Sulphur cloud rose above the crater and 7m gas bubbles were reported in the lake. Variations in temperature have been reported through the years and further smaller gas eruptions were reported in 1957. During April 1993 three gas explosions occurred with a height of 10m accompanied by a strong sulfur smell and a shift in colour of the lake shifted to whitish green. There was a swarm of earthquakes occurred to the South West of Kawah Ijen in May 2011. The significant changes in volcanic activity affected the shallow portions of the volcanic system and led the authorities to increase the volcanic alert level to 3. Recent Activity In May 2020 a volcanic tremor at Mount Kawah Ijen in East Java triggered the release of poisonous gas and a 3 m high tsunami. The tremor resulted in toxic bubbles of air being released and waves in the crater lake. Local media confirmed that a sulfur miner was found dead a day after. Discussion While the blue flames and Sulphur mining catch our attention, what catches my eye is the 1817 eruption impacts downstream. The volume of acidic water that seems to have made its way down stream seems to exceed the size of the lake at that time suggesting to me a reservoir of acidic water beneath the volcano. Human populations down stream do not seem that large, but agriculture would certainly be devastated downstream. Despite water being diluted as it goes downstream it seems to me that very little consideration has been given to the effects on ocean marine environments with the volumes of heavy metals which could be released into the ocean.
  7. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mount Natib Reason for Interest There are not many active volcanoes with mothballed nuclear power plants on them that some are proposing to reopen. While the debate about that goes on other risks might be slightly ignored. Whilst I doubt Mount Natib will produce a really big eruption it can potentially disrupt the lives of a very large population. The Setting Luzon is the largest and most populous island in the Philippines. It is the economic and political center of the nation, being home to the country's capital city, Manila, as well as Quezon City, the country's most populous city. The central section of Luzon is characterized by a flat terrain, known as the Central Luzon plain, and is the country's largest producer of rice. The western coasts of Central Luzon are typically flat extending east from the coastline to the Zambales Mountains, the site of Mount Pinatubo. These mountains extend to the sea in the north, forming the Lingayen Gulf, and to the south, forming the Bataan Peninsula. The peninsula encloses the Manila Bay, a natural harbor considered to be one of the best natural ports in East Asia, due to its size and strategic geographical location. Bataan is a province situated in the Central Luzon region of the Philippines and occupies the entire Bataan Peninsula. The City of Balanga is the capital of the province of Bataan with a population of approximately 100,000. Bataan is bordered by the provinces of Zambales and Pampanga to the north. The peninsula faces the South China Sea to the west, Subic Bay to the north-west and encloses Manila Bay to the east. The US Naval base at Subic bay base covers 262 square miles and was the largest overseas military installation of the United States Armed Forces. Following its closure in 1992, it was transformed into the Subic Bay Freeport Zone by the Philippine government. It is now one of the busiest ports in the Philippines and host the Subic bay international airport. Located in Orani on the slopes of Mount Natib is Bataan National Park which is the last remaining closed canopy dipterocarp forest in the whole Central Luzon. It is home to giant fruit bats, wild monkeys, wild boars, civet cats, eagles, and pygmy woodpeckers along with fruit-bearing trees, including coffee, jackfruit, guyabano, and lanzones. Covering about 23,688 hectares, the Bataan National Park is also the home to the Pasukulan falls and the Dunsulan falls. Forests extend from Subic Bay National Park up the north-western slope of Mt Natib in Bataan National Park. These are one of the few remaining undisturbed forests that face the South China Sea. The lowlands around Subic Bay National Park are now predominantly agricultural land and human settlements. The lower slopes of the mountains are covered by grasslands and croplands while old growth forest is mainly confined to the steep slopes and gullies at higher altitudes. Much of the forest was damaged by ash from the Mt Pinatubo eruption in 1992. The Tectonic environment The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Pacific plate is subducted into the mantle from south of Japan extending down the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. Along its western margin, the Philippine Sea plate is associated with a zone of oblique convergence with the Sunda Plate. This highly active convergent plate boundary extends along both sides the Philippine Islands, from Luzon in the north to the Celebes Islands in the south. On the west side of Luzon, the Sunda Plate subducts eastward along a series of trenches, including the Manila Trench in the north. Studies have identified the Lubao Fault in Pampanga from a prominent surface lineament trending southwestward across deltaic plains north of Manila Bay. Field mapping and remote sensing has shown that the fault extends southwestward through Mount Natib Volcano into the South China Sea, and presently may be undergoing 3.2 cm/y of right-lateral motion. The active Lubao Fault extends southwestward from the plains north of Manila Bay to cut through Natib and emerge at the BNPP inactive nuclear power plant. The Volcano Mount Natib is a massive stratovolcano located at the northern end of the Bataan Peninsula, Luzon Island, Philippines. Mount Natib lines up with Mount Mariveles to the South and Mount Pinatubo to the North . It is topped by a 7 kilometer acorn shaped Caldera that is open to the northwest with the smaller younger 2 kilometer wide Pasukulan Caldera to the east of the main caldera. The highest peak of Mount Natib has an elevation of 1,253 metres and is at the point of convergence of the two calderas. The breach in the caldera is the most likely source of a pyroclastic deposit in the eastern which indicates a Natib eruption occurred much more recently than previously thought. Current activity on Natib is through five thermal areas with hot springs have temperatures ranging from 30-56 °C. Mount Pinatubo Mount Pinatubo is located north east of Mount Natib which on 15th June 1991 had one of the largest volcanic eruptions of the 20th century. This is thought to have been triggered by a large earthquake in July 1990 60 miles north on a fault line that passes through Pinatubo. It is estimated that ash was propelled more than 30 km into the air and pyroclastic flows extended more than 10 km from the summit of Mount Pinatubo. Pyroclastic flows traveled as much as 12 to 16 kilometers from the vent in all sectors. Pyroclastic flows crossed a 400m high ridge 3km away and a further 100m ridge further away. Before the eruption Pinatubo was considered dormant much like Mount Natib. Krakatoa The tsunamis which accompanied the eruption of Krakatoa were believed to have been caused by gigantic pyroclastic flows entering the sea. This caused several cubic kilometers of material to enter the sea, displacing an equal volume of seawater. The town of Merak was destroyed by a tsunami which was 46 meters high. Some of the pyroclastic flows reached the Sumatran coast as much as 40 km away having apparently moved across the water on a cushion of superheated steam. Nuclear Power Station On the South West part of the volcano is the site of a mothballed nuclear power plant that has caused arguments about proposals to activate. The site is 5km from the volcano caldera and is underlain by lava flows, lahar deposits and at least six pyroclastic deposits. It is argued that because the area is now on a ridge compared to the surrounding land that the lahar risks are low and that pyroclastic flows are more likely to flow down the breach in the caldera to the north west. Global standards do recommend that nuclear facilities are not within 1km of an active fault so it remains mothballed for now until further investigations can be done. Manila Metropolitan Manila lies in a coastal region along the Manila Bay about 80km across the bay from Mount Natib. It is flat and low-lying terrain with elevations ranging from 0 to 1 meter above mean sea level. Metropolitan Manila faces the South China Sea and is thus exposed to the south-west monsoon. Metropolitan Manila has suffered serious flood damage mainly caused by overtopping of the main rivers and inland water bodies. In September 2011, Typhoon Nesat passed about 200 km north of Manila Bay and was one of the most destructive storms to affect the coastal areas of Metro Manila. The storm surge began early in the morning, with seawater spilling on streets by 8am then huge waves caused portions of the sea wall to collapse. It has been reported that more than 6,000 flood control projects have been completed to protect flood-prone areas across the country yet still parts of Manila flood regularly. Discussion Not being an expert I prefer not to comment on the nuclear power plant, but I think you could argue that any activation of Mount Natib whether through earthquakes or other means could pose a flooding threat to the Manila Bay area. The omission in the discussions for me is the threats to the Subic Bay area , to the City of Balanga and the towns around the volcano. I Guess it interests me that there is a distraction from the obvious hazards of this volcano. It is not likely to erupt on the same scale as Krakatoa or Pinatubo but seems to me a sleeping danger to a large population.
  8. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Ilopango Caldera Reason for Interest The caldera is the result of an eruption 10 times the size of the St Helen's eruption which potentially changed the worlds climate and affected millions worldwide. When we focus on big events we tend to lose sight of other smaller hazards and for me there is one to watch out for here. Whilst another big eruption is unlikely a resumption of activity could make the lakes water more poisonous affecting roughly 3 million people who use it as a source. The Setting El Salvador is a small central American Pacific Coast country with Honduras to the North and East and Guatemala to the West with an Ocean to the south. The Sierra Madre Mountain range is in the North along the border with Honduras. Further south is the coastal Mountain range which is split into five groups of active volcano groups. The lowlands along the coast have a tropical climate with mango, coconut and Cashew trees, the plateau between the mountain ranges has a semitropical climate and mountain areas experience more temperate weather with pine and oak. Temperatures typically ranging from 60 to 85 Degrees Centigrade with a wet winter season from May to September. The wet season rain comes from low pressure systems forming in the Pacific often leading to Thunderstorms (often in the afternoon or overnight). The country has frequent earthquakes with a history of significant damage to buildings in the past. The economy is notable for indigo, coffee, fruit and more recently for surfing. Due to the use of the U.S. Dollar as a currency El Salvador is becoming more Americanised with shopping malls and boutique Hotels beginning to crop up. Parts of El Salvador are troubled by gangs and corruption so it can be risky to visit despite its growing Americanisation. El Salvador is known for its gorgeous flowering trees, the Maquilishuat the pink-tufted national tree, the beautiful Roble Colorado with its fuchsia and the Arbol de Fuego a tree with brilliant orange flowers. This is also home for armadillos, anteaters, sloths, ocelots, jaguar, spider monkeys, parrots, parakeets, boa constrictors, turtles, coatis and the national animal the Turquoise-Browed Motmot. The Tectonic Environment Most of Central America rests on the relatively motionless Caribbean Plate. The Cocos Plate close offshore in the Pacific is being carried northeast and subducting below the Caribbean Plate. The Pacific relatively dense ocean floor is forced down under the lighter land mass, creating the deep Middle America Trench that lies off the coast of El Salvador. The subduction of the Cocos Plate accounts for the frequency of earthquakes near the coast. As the rocks of the ocean floor are forced down, they melt, and the molten material pours up through weaknesses in the surface rock feeding volcanoes. The Caldera The scenic 8 x 11 km Ilopango caldera, filled by one of El Salvador's largest lakes, has a scalloped 150-500 m high rim and reaches 300m deep. The caldera, which lies immediately east of the capital city of San Salvador, is strongly controlled by regional faults of the central Salvador graben(rift). Four major explosive eruptions during the late Pleistocene and Holocene produced extensive pyroclastic flows and deposits that blanket much of El Salvador. The latest collapse resulted from the massive Terra Blanca Joven eruption devastated early Mayan cities. Post caldera eruptions formed a series of lava domes within the lake and near its shore. The Islas Quemadas, a group of low islets in the center of the lake that mark the summit of a largely submerged lava dome were formed in 1879-80 during the only historical eruption of Ilopango. More than 200,000 inhabitants live in the drainage basin of Ilopango lake, El Salvador, even though high concentrations of boron and arsenic make this water unsuitable for human consumption. The Rio Desagüe drains water from Lake Ilopango into the Jiboa River which then goes south into the Pacific Ocean. The river does not appear natural and the names in the area support the idea that the Maya created the river by blasting a channel using gunpowder. I have a reputation for being a site for UFO visitations and many visit me specifically to see UFO's. Past Eruptions The Islas Quemadas dome in Lake Ilopango, El Salvador, was extruded during December 1879 to March 1880. The eruption took place in six distinct periods, five of which began near fortnightly minima in the amplitude of the semidiurnal solid earth tide. An earthquake swarm preceded dome extrusion. The Tierra Blanca Joven eruption In the summer of 536 AD a mysterious cloud appeared over the Mediterranean basin and local climate cooled for more than a decade causing crop failures and widespread famine. Researchers say there were two volcanic eruptions with the first in 535 or 536 in the northern hemisphere and another in 539 or 540 in the tropics that altered the world climate. Suspicion has been that the 540 eruption was due to the Ilopango eruption in El Salvador although although other candidates are El Chichón in Mexico or the Haruna eruption in Japan. There are problems with the argument that Ilopango Tierra Blanca Joven eruption was responsible for this climate change period. The first is the research by Victoria Smith of Oxford University who analyzed an ice core recovered from Greenland and also carried out radiocarbon measurements from a charred tree found in the TBJ ash deposits and accurately dated the eruption to 431 CE. The next issue is the examination of the ice core GISP2 from Greenland which showed high levels of tropical sea water fossils in the ice for the 540 period. From examination of the Colle Gnifetti Glacier ice core in the Swiss Alps researchers found particles which resembled volcanic rocks from Iceland and dated them to 536 AD. Other research by Robert Dull however identified that there were 8 phases of eruption by Ilopango which were close together so a single year for the eruption might be a stretch. This research also looked at three tree samples which gave mixed results. The first showed an earlier date and the second two suggested an eruption around 540 AD. Recent Activity Ilopango has an active hydrothermal system and Divers have reported increasing seepage of hot water in the south of the lake near the Cerro Los Patos island. The area between the Islas Quemadas and the lake’s southeast margin also experienced the most frequent seismicity of any lake sector. Discussion The arguments about the source of the 536 to 540 climate changing eruption will go on, but we should not let that distract us from other hazards, like hydrothermal activity increases affecting the water quality. Just watch out for the UFO's though.
  9. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mombacho Reason for Interest Sometimes a volcano highlights a hazard which is not so obvious yet has clear evidence of the risks in its history. In this case the hazard is massive landslides and tsunamis within an inland lake. Whilst this volcano may not have much opportunity for further collapse there are other volcanoes nearby which pose a equal risk. This risk does not even require volcanic activity to be realized. The Setting Mombacho Volcano is in Nicaragua the largest country in the Central American isthmus, bordered by Honduras to the northwest, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the southwest. On the Pacific side of Nicaragua are the two largest fresh water lakes in Central America Lake Managua and Lake Nicaragua. The Pacific lowlands zone of Nicaragua has temperatures which remain virtually constant throughout the year, with highs ranging between 29.4 and 32.2 °C. After a dry season lasting from November to April, rains begin in May and continue to October, giving the Pacific lowlands 40 to 60 in of precipitation. Punctuating this plain are several large volcanoes of the Cordillera Los Maribios mountain range, including Mombacho just outside Granada. The North and Central highlands enjoys milder temperatures with daily highs of 23.9 to 26.7 °C. About a quarter of the country's agriculture takes place in this region, with coffee grown on the higher slopes. Oaks, pines, moss, ferns and orchids are abundant in the cloud forests of the region. The sparsely populated Caribbean lowlands has large rain forests with the climate being predominantly tropical, with high temperature and high humidity. The Tectonic environment The west coast of Nicaragua and Central America is a convergent margin where oceanic crust of the Cocos plate which is part of the Pacific Ocean plate is being subducted beneath the western edge of the Caribbean plate. A volcanic arc with active volcanoes, earthquakes, and steep mountains has formed above this convergent margin subduction zone. The Mombacho volcano stands on the Central American Volcanic Front which in Nicaragua aligns along the edge of the Nicaraguan depression. The Nicaraguan depression which contains Lakes Nicaragua and Managua is a 100km wide depression extending 342 km across the length of Nicaragua. The exact reason for the depression is hotly contested but seems to be due partially to the plate convergence crumpling and partially due to subsidence of blocks of crust. It is argued that these blocks are twisting due to the angled convergence of the plates with the result that each block has compression and extension sections as it tries to rotate. The Volcano Mombacho is a 1345m High stratovolcano located 12km South of the city of Granada bounded by lake Nicaragua to the east and by Apoyo Caldera a few kilometers to the North West. Current activity consists of fumaroles and hot springs within the 2 collapse scarps and on the upper northern flank. At least three large-volume debris avalanche deposits have been attributed to Mombacho and resulted from catastrophic flank collapse. The long runout of the northern deposit reached Lake Nicaragua and formed the peninsula and cluster of islands, Isletas de Granada 11 km NE from Mombacho's summit. The northern landslide scar is shallow-rooted and cuts the volcano’s flanks down to the base and show little evidence of hydrothermal activity. This suggests the landslide is unlikely to have been caused by eruptive activity. Parts of the landslide include basement rocks suggesting the failure went down into the substrata. It has been proposed that this indicates spreading under this part of the volcano. Forest cover indicates the landslide is at least 1000 years old while underlying deposits suggest that it is younger than 20000 years. The southern landslide in contrast has a high content of extremely altered material provides evidence that the rock mass suffered intensive hydrothermal alteration before the collapse. Historical archives infer that the trigger to this avalanche may have been continuous swarms of seismic activity concluded by an earthquake in 1570. Accounts from the time suggest the 1570 debris flow at Mombacho was similar too the 1998 flow at Casita where intense rainfall triggered the landslide. A third landslide deposit can be found south east of the volcano but is hidden by eruption deposits. The lower two-thirds of this mountain is reserved for agriculture. But higher up the peak the flora is a mix of dry forest and savannah trees with coffee plantations mixed in below the trees. At the highest levels are the cloud forest that form the nature reserve. The Mombacho Volcano Nature Reserve has a wide variety of trees and plants that thrive on the mountain due to the cloud forest’s humidity you can also observe howler and white face monkeys, snakes, deer, reptiles, birds and insects. There are several endemic species living on Mombacho including the Mombacho salamander. The Casita landslide In late October and early November 1998 torrential rains of Hurricane Mitch caused numerous slope failures in Central America, the most catastrophic of which occurred at Casita volcano in Nicaragua. On October 30, 1998 residents south of the Casita volcano in Nicaragua heard a roaring noise like helicopters or thunder. Soon after a wave of muddy debris 1km wide and 3m deep roared down the Volcano destroyed all traces of two towns. On the apron of the volcano where the flow spread out, survivors describe the flow as “an infernal wave of mud, rocks, and trees,”. The debris flow moved about 10 km from its source and generated floods that moved an additional 10 km downstream, destroying roads and bridges and inundating homes. Discussion While the chance of a landslide towards the city of Granada is low with collapse to the north East already having occurred there is still a possibility of a slide into the lake on the East. Further down the lake is the Concepción Volcano which is constructed similarly yet with no slides so far. The risk of a lake tsunami seems possible and there is a large population within ones reach. At the very least it is worth highlighting a possibility.
  10. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing The Tongariro volcanic complex Reason for Interest This complex of Volcanoes are capable of significant eruptions and have been quiet in recent years. Despite being in a remote area there is infrastructure in the form of electricity and water supplies along with transportation routes which can be threatened by volcanic activity. Besides who can resist Mount Doom from the Lord of the Rings Films. The Setting The Volcano Complex is found in New Zealand, an island country in the southwestern Pacific Ocean. It consists of two main land masses the North Island (Te Ika-a-Māui) and the South Island (Te Waipounamu) and more than 700 smaller islands. The two main islands are separated by Cook Strait which is 14 miles wide at its narrowest point. The country's varied topography and sharp mountain peaks, including the Southern Alps, owe much to tectonic uplift and volcanic eruptions. The capital city is Wellington and the largest urban area Auckland are both are located on the North Island. New Zealand's geographic isolation for 80 million years has influenced evolution of the country's species of animals, fungi and plants. Physical isolation has resulted in a dynamic evolution with examples of distinctive plants and animals. Over 20 percent of New Zealand is covered in national parks, forest areas and reserves with two World Heritage Areas, Tongariro in the Central North Island and Te Wahipounamu in the south-west of the South Island. New Zealand’s climate varies wildly with the far north having subtropical weather during summer, while inland alpine areas of the South Island can be as cold as -10°C in winter. Most of the population lives close to the coast with mild temperatures all year round. January and February are the warmest months, and July is the coldest month of the year. Today, the population of New Zealand is made up of people from a range of backgrounds. The Maori indigenous people, of New Zealand arrived more than 1000 years ago from their mythical Polynesian homeland of Hawaiki. Today, one in seven New Zealanders identify as Maori. The Tectonic environment New Zealand is located on the boundary beneath the Australian and Pacific Plates. Beneath the islands the Pacific Plate is being subducted beneath the Australian Plate. As the Pacific Plate sinks deeper into the Earth it is partially melted by the friction and the heat of the planet's interior. Some of the melted material then rises through the overlying Australian Plate, fueling the volcanoes of New Zealand. The East Coast of the North Island is rotating clockwise, relative to Northland, Auckland and Taranaki, stretching the Bay of Plenty, and producing the Hauraki Rift and Taupo Volcanic Zone. The Taupo Volcanic Zone is a NE trending arc of volcanic activity that has been the focus of volcanism in New Zealand. The central zone has a relatively thin crust with a thickness of about 15 km owing to active faulting and extension. The most recent activity in the zone has been concentrated within the Tongariro Volcanic Centre. The Tongariro Volcanic Centre is at the southern most extent of the Taupo rifting zone with the volcanoes along an actively extending graben (rift) about 18km wide. Total basement subsidence is estimated at 650m with the the rifting being accommodated by a mixture of Magma filling and fault slipping. Steep-sided volcanic bodies coincide with the Waihi fault and the rift axis suggesting that this fault system may have provided magma pathways to the surface. Study of previous eruptions suggest that at times the fault has unzipped causing eruptions from many vents at the same time. This resulted in very large eruptions from all the volcanoes in the Tongariro Volcanic Centre at the same time. Tongariro volcano Mount Tongariro which means ‘fire carried away’ or ‘seized by the cold south wind’ is part of the Tongariro volcanic center. There are many explosion craters on the volcano complex with water filling some of these to form the Blue Lake and the Emerald Lakes. Red Crater last erupted ash in 1926 and contains active fumaroles. Ketetahi Springs, on the northern side of Tongariro, is a collection of hot mineral springs and steam vents (fumeroles). Three 220 kV electricity transmission lines are within 15km of the volcano along with Hydro-generation facilities and water from the area is used as a source of drinking water. On 6 August 2012, Mt Tongariro had what was initially believed to be a hydrothermal eruption after a month of increased activity. The eruption occurred at the Te Mari Craters which had been dormant since 1897. The eruption occurred in a new vent below the Upper Te Mari crater, and sent blocks as large as 1 meter in size up to a mile from the vent. An ash cloud 4 miles high deposited ash into the surrounding area, especially to the east of the volcano. The ash cloud was very large with the smell of sulphur reported as far away as Wellington. Ngauruhoe Volcano Mount Ngauruhoe (throwing hot stones in Maori) which some may recognize as Mount Doom from Lord of the Rings is one of the most famous volcanoes in New Zealand. Ngauruhoe isn’t actually a volcano on its own, but rather a cone of the larger Tongariro Volcanic Complex, which resides in the Tongariro National Park. At 2291m high it is the highest point of the Tongariro complex. Ngauruhoe is the youngest (7000 years old) and one of the currently active vents of the Tongariro Volcanic Centre alongside the Te Maari craters, Emerald Lakes, North and Red craters. The Ngauruho eruptions have been fed from a series of small complex interconnected magma chambers that are part of a larger system underlying the area. The summit of Ngauruhoe is currently composed of two craters, an older outer crater with a diameter 450m and a younger inner crater formed in the NW sector of the outer crater that is approximately 220m in diameter. Fumaroles exist in the inner crater and on the rim of the eastern and northern outer crater. Up until 1975 the volcano erupted roughly every 9 years but has not erupted since then. During both 2006 and 2015 earth quake swarms were detected but no eruption occurred. An eruption commenced in June 1954 when lava fountaining was observed reaching 300m above the Crater Rim and producing lava flows down the northwestern sector. Fire fountaining and ash emission continued throughout July with more lava flows descended down the western slopes. Near continuous emission of black ash occurred and incandescent blocks were thrown onto the northern slopes of Ngauruhoe. During September Multiple loud explosions produced visible shock waves and dark ash clouds that rose above the crater to about 1.2km and deposited ash as far away as Taupo township. The first activity of the 1974-75 eruption was of a black cloud and the ejection of incandescent bombs that lit up the summit flanks. Partially collapsing ash columns resulted in pyroclastic flows and large blocks and bombs reaching 5m diameter were ejected reaching the lower flanks of the volcano. Activity reached a climax on February 1975 with the largest explosion of the eruption episode with an ash cloud reaching 6000m. Mount Ruapehu Ruapehu located within Tongariro National Park is the largest active volcano in New Zealand and is the highest point in the North Island. It has three major peaks which are Tahurangi (2,797 m), Te Heuheu (2,755 m) and Paretetaitonga (2,751 m). The deep, active crater is between the peaks and fills with water between eruptions with the lake being known as Crater Lake which is filled with acidic water. The lake's outlet is at the head of the Whangaehu Valley which is notorious for destructive lahars caused by Ruapehu's eruptions. In historic times, eruptions have built tephra dams across the outlet on several occasions, most recently in 1945 and 1996. These dams failed in 1953 and 2007 respectively, causing an outburst of Crater Lake each time, which sent destructive lahars down the river. A total of 18 glaciers have been recognized on Ruapehu with two glaciers found in the active crater. These are New Zealand's only crater glaciers with one crater on the north side of the crater under Paretetaitonga Peak and the other one to the south. Due to altitude and snow cover Ruapehu is home to the North Island's major ski resorts, Whakapapa on the northern side and Turoa on the southern slope. The season is generally from June to October but depends on snow and weather conditions. Ruapehu entered an eruptive phase in March 1945 after several weeks of volcanic tremors. The first indication of an eruption was reported on 8 March, with ashfall seen on the eastern slopes. A lava dome was observed in Crater Lake on 19 March but was destroyed in a series of explosive eruptions over the following week. A second, larger lava dome appeared in May, which continued to grow over the following months and had emptied Crater Lake of water by July. A particularly powerful eruption in the early hours of 21 August was heard in Hawkes Bay and the Tararua District, loud enough to awaken people from sleep and cause alarm. Eruptions began declining in December and had ended by January. On 24 December 1953, a debris dam near the lake outlet collapsed, sending an ash-laden lahar down the Whangaehu Valley. Soon after the lahar swept away the Tangiwai rail bridge, the Wellington-Auckland express plunged into the swollen river, killing 151 people. Ruapehu saw a period of heightened activity between 1966 and 1982, with multiple small eruptions occurring in Crater Lake and two larger eruptions in 1969 and 1975, which ejected rocks across the summit region and produced significant lahars. The eruption in 1969 was a moderate phreatic eruption, which blasted rocks up to 1km northwest of the crater and sent lahars down several valleys. Earthquake swarms to the west of Ruapehu between November 1994 and September 1995 marked the beginning of renewed heightened activity at the volcano. The first significant eruption took place on 18 September 1995 raining tephra onto the summit region and sending lahars down the mountain. On 23 September, an even larger eruption blasted rocks up to 1.5 km from the crater, sent lahars down three valleys, and generated an eruption column 12 km High with ash fall occurring up to 250 km downwind. During July and August eruption columns reached more than 10 km high and shot rocks 1.4 km from the crater. These eruptions produced more than 7 million tons of ash, which contaminated water supplies, destroyed crops, and lead to the deaths of livestock. Ash in the Tongariro River also damaged the intake turbines at the Rangipo power station, and ash clouds caused airport closures as far away as Auckland and Wellington. Ruapehu erupted in October 2006 marked by a magnitude 2.9 volcanic earthquake and sent waves 5 meters tall crashing into the wall of the crater. On 18 March 2007, the tephra dam which had been holding back Crater Lake burst sending a lahar down the mountain. Discussion Emerald lakes, ski slopes, and photogenic scenery may suggest a benign environment but history suggests these are dangerous volcanoes. What piques my interest is that when considering volcano hazards we need to consider things which are not immediately obvious like infrastructure.
  11. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing the Tunnel to Atlantis and Jameos Del Aqua Reason for Interest Perhaps it is because it is one of the spiritual homes of Vulcanology or perhaps it is a place I have seen it and been stunned by. This really is one of the wonders of the world and it is my pleasure to introduce you to despite this straying a little from previous posts which were more volcano focused. The Setting Lanzarote is located 7 miles north-east of Fuerteventura with dimensions 37 miles from north to south and 16 miles from west to east. Lanzarote and its geologically similar neighbour, Fuertaventura are the oldest canary islands. Often called the "Island of Eternal Spring" Lanzarote has a subtropical desert climate with the small amount of precipitation mainly concentrated in the winter. Rainfall during summer is a rare phenomenon and very often summers are completely dry without any precipitation. Sometimes, the hot sirocco wind prevails, causing dry and dusty conditions across the island. Life changed with the development by naval engineer Manuel Díaz Rijo of the first early desalination plant. Lanzarote has been a benchmark in which other parts of the world have been inspired to treat water. Plants have adapted to the relative scarcity of water in the same way as succulents and include the Canary Island date palm which is found in damper areas of the north, the Canary Island pine, ferns, and wild olive trees. Settled by the Genoese, Lancelotto Malocello in the early 14th century, Lanzarote’s volatile past had created large mountain ranges in the north, at Famara, and in the south at Ajaches. But the island was to witness the longest volcanic eruptive incident in history when, in 1730 the land around Timanfaya opened up and for the next six years rained fire, lava and ash across the face of the island, blocking out the sun and altering the landscape beyond recognition. The 1730 eruption of Timanfaya was the third largest basaltic fissure eruption of historical times, after Laki and Ejdgja in Iceland. It lasted 68 months and produced 700 million cubic meters of lava from over 30 vents. It was the largest Canary Island eruption within the last 500 years. Away from the tourist centers you will find an island of uniform, white houses standing proud against their volcanic palette of muted colours. At its northern center the still proud former capital of Teguise has given over its quaint cobbled streets and pretty houses to artists and restaurants while the windy northern cliffs and endless golden sands of Famara provide an unrivalled playground for surfers. At the playa Orzola or Carleton Blanco beaches in the north can be found a wonderful sandy beachs with virtually no visitors. The Museo Atlantico can be found offshore on the seabed near Playa Blanca which is the brainchild of Jason deCaires Taylor where between 12 and 15 meters below the waves lies a raft haunted by sculpted refugees, a sunken couple taking a selfie and rows of Lanzarote residents immortalized in the Atlantic. César Manrique Born in Lanzarote he moved to Madrid where he studied at the Academia de Bellas Artes de San Fernando and graduated as art professor and painter. He prospered in Madrid, Paris and New York and became an internationally acclaimed artist, whose paintings were exhibited across Europe as well as in Japan and the United States. He returned to Lanzarote in 1968 with the intention to make it one of the most beautiful places on the planet. With his imagination bizarre volcanic forms were adapted and converted into unique pieces of art in complete harmony with their natural origins. Due to Manrique Lanzarote has been spared the worst of over development who persuaded the powers that be to forbid the building of high rise hotels and the display of advertising billboards. While there has been a large amount of construction, dwellings on Lanzarote retain a minimalist simplicity, externally, being painted only in white, green and blue. The Tectonic Settings The island of Lanzarote is located is in the north eastern part of the canary islands and in alignment with the island of Fuerteventura. The two islands constitute the emergent part of the East Canary Ridge a volcanic structure located on the oceanic crust. The East Canary Ridge consists of several uplifted blocks of oceanic basement mantled with Lanzarote having a shallow basement, probably about 4–5km thick as deduced from seismic profiles. The origin of magmatism in the Canaries have been a subject of debate for a long time and it is popularly believed that the origin of oceanic intraplate volcanism is related to a mantle plume or Hot spot. With the most youthful islands being in the west this would suggest a migrating hot spot, but would not explain why Islands like Lanzarote see renewed volcanism. Other theories which have been suggested are a propagating fracture which is an extension to the trans-Agadir fault, a local extensional ridge: there was a regional extensional structure, uplifted tectonic blocks, a unifying model suggesting the origin of the magmas is a mantle anomaly. Probably the best explanation I have seen is that rather than a plume from the mantle boundary that there is a broken subducted sheet which finds it way upwards through fractures caused by twisting of the crust due to the rotation of the Maghreb sub plate. Lava Tubes During long eruptions lava flows tend to become channeled into a few main streams. Lava streams that flow steadily in a confined channel for many hours to days may develop a solid crust or roof and, thus, change gradually into underground lava streams called lava tubes. When the supply of lava stops at the end of an eruption lava in the tube system drains leaving partially empty conduits beneath the ground. This leaves a partially empty tube that is called a lava tube cave. Roof collapses of lava tubes are rather common as the roofs tend to be rather thin as a result of the way it formed. Jameos del Agua Jameos del Agua is a series of lava tubes in northern Lanzarote which Hollywood actress Rita Hayworth once described as the eighth wonder of the world. The lava tunnel was created by lava flows that emerged from the La Corona volcano in Haria some 21,000 years ago. It is 6km in length, 1.5km of which runs under the sea. The whole lava tube structure is known as the Tunnel to Atlantis due to the large section submerged under the sea. César Manrique’s on his return to Lanzarote in the 1960s took on a project to transform part of the partially collapsed lava tube into a glamourous blend of architecture and nature to show off how architecture can be used to maintain the harmony between man and nature. He took a partially collapsed section of the lave tube and built a nightclub, swimming pool and concert hall which has become the tourist attraction known today as Jameos del Aqua. A winding volcanic staircase lined with leafy vegetation leads you into the first smaller cave, Jameo Chico. At the bottom of the staircase you find a natural saltwater lagoon which is home to several rare species of white blind crabs. Skirting around the lake you come to a wining and dining area with a dance floor. This is home to the Jameos Music Festival, and has been described as the best nightclub in the world. Following a winding path upwards there are a number of secluded seating areas in various nooks and crannies and a small bar tucked into the cave wall. Climbing further up you enter into an open area the Jameo Grande where the tube roof has collapsed. Here you will find a black lava walled sunken area with lush tropical vegetation and lots of nooks and crannies with wooden benches for sitting. In the center you will find a scalloped luxury white floored swimming pool which nowadays only the King of Spain can swim in. The merging of nature and architecture is like nothing else on the planet and looks like a film set. Leading of from this are through a set of glass doors is a further cave Jameo Cazuela which has been transformed into an underground concert hall. The auditorium hosts regular music concerts, theatrical performances and even the annual film festival. Going back to the pool area and climbing a set of stairs will lead you to the Casa de los Volcanes (House of the Volcanoes) which is an avantgarde building that houses some fantastic information about the island of Lanzarote. The Casa de los Volcanes hosts an annual meeting of international volcanologists and also provides occasional talks about volcanoes to the general public. Discussion You do not need to be a volcano fan or interested in Science to be interested. Whether the mixture of nature and concrete is to your taste I will leave to you. Are there other places you have seen which have captured your imagination.
  12. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Furnas Reason for Interest Sao Miguel is Another beautiful island with explosive volcanoes with typical volcanic repose times of 300 years which makes activity more likely in the near future. What really catches my eye though is the fact that some villagers live in houses where CO2 levels can get dangerously high currently. The Setting Located off the west coast of Portugal is the Azores, a slice of heaven in the form of a nine island archipelago. Sitting approximately 1,643 km from Lisbon, Sao Miguel is the largest island (40 miles by 10 miles) in the Portuguese Azores archipelago. Sao Miguel is famous for it volcanic landscape peppered with bubbling geysers, colourfull flora and rich marine life, including whales and dolphins. Known as the "green island" or "Hawaii off the Atlantic" São Miguel is the center of government and the Azores. Important industries include agriculture, fishing and tourism. The island grows tea and tobacco and is known for its diary farming. Flank volcano collapses and high magnitude sea cliff landslides are known to have occurred in several Azores islands. The major reported landslide-triggered tsunami took place in 1847, when a rotational slide occurred in a sea cliff with more than 350 metres high at the NW coast of Flores Island. The entrance of material into the sea originated a wave that affected both Flores and Corvo islands, being responsible by the death of 10 people and more than 100 injured. In the last 500 years at least 12 tsunamis generated by earthquakes or landslides reached the Azores archipelago. Recent studies revealed that the highest magnitude event was the tsunami generated by the 1755 Lisbon earthquake with had an epicentre in the North Atlantic and had a maximum run-up of about 15 metres. One major earthquake occuring in 1757 killed more than 20 percent of the population of Sao Jorge island and the largest measured event in 1980 on Terceria island had a magnitude of 7.3. Several major landslides have occured on Sao Miguel including the one which destroyed the previous capital of the island Vila Franca do Campo. São Miguel has a subtropical climate and similar to other islands in the archipelago, São Miguel is influenced by ocean currents and winds, and, in particular, the cyclonic Gulf Stream. This stream functions as a moderating force in the islands, keeping temperatures hovering between 14 °C and 23 °C throughout the year. The island's location also makes it susceptible to some Atlantic storms, and precipitation tends to be elevated during the winter periods. In the east of the island is Furnas volcano and nestled within the crater is the town of Furnas. It is surrounded by lush green vegetation and home to the famous Terra Nostra Botanical Gardens where you can swim in the mineral rich healing volcanic waters that flow at a constant 35 to 40 degrees Celsius. The Tectonic environment The main tectonic features that dominates the Azores region is the spreading Mid-Atlantic Ridge (MAR) which runs North to South to the west of most of the Azores. To the south is the Azores Gibraltar Fracture Zone that constitutes the Eurasian Nubian (Europe and Africa boundary) plate boundary and extends from the MAR to the region of Gibraltar. Most of the Azores lie in the Terceira Rift (TR) fault which is an complex rift fault zone trending NW to SE extending from the MAR to the Gloria Fault. The concept of an ‘Azores mantle plume’ has been widely debated, and the existence of an Azores hotspot questioned. An alternate explanation is an enriched upper mantle domain with more volatiles than normal or Decompression of a wet mantle caused by rifting tectonics. Another explanation proposed is a block tectonic model for the Azores Rise that has multiple blocks. They move relative to one another in strike – slip motion or rotate clockwise depending which fault systems are active. This swapping back and forth of motions controls buildup of volcanoes and current seismic activity. Interestingly two shallow depth velocity anomalies have been identified with one below Faial, Pico, and Graciosa and the other between Terceira and Sao Miguel so perhaps two hotpots rather than an actual plume. The Volcano Furnas is the easternmost of the trachytic active central volcanoes of São Miguel and is thought to be the youngest volcanic center on the island. In the last 5000 years Furnas has had 10 moderately explosive eruptions. Two of these have taken place since the island was settled in the mid-fifteenth century. There are at least two calderas, a younger one that is 6-km wide and a larger older 8 km wide. The eastern wall of the 500-m-deep Furnas inner caldera overlaps the western wall of the Nordeste Povoaçao caldera. The southern rim of the volcano is cut by marine erosion to form high steep cliffs. Young pumice cones (less than 5000 years old) are distributed on the floor of the inner caldera. Since the early 1990s geochemical studies carried out in São Miguel Island showed that some villages are placed in anomalous high degassing areas, and indoor measurements performed in various dwellings highlight the risk to the population. These high indoor CO2 concentrations are not only measured in areas classified as high degassing areas, but lethal CO2 concentrations are also registered in buildings located in areas previously defined as low- and medium-risk zones. Beneath the crater lake degassing plumes have been found in the north of the lake. The highest density of degassing plumes correlates with recent submerged secondary craters formed around the caldera rim. More recent mapping of the lake floor (Lagoa das Furnas) also revealed a volcanic cone in the southern part of the lake. Analysis of deposits nearby suggest this was formed as part of the 1630 eruption. Past Eruptions Some time between 1439 and 1443 a Portugese priest entered the valley of Furnas and reported tongues of fire and tremors with vapour rising from the three lakes. It is thought this corresponds to the latest eruption from the Gaspar dome. Several first hand observations have been recorded of the most recent 1630 eruption. One reports clouds of fire from two of the lakes and an explosion that blew away the elevation between two lakes. Another observation reports on ash which turned day to night with tremors which made the whole island feel like it was in a swale. It seems likely that of the three lakes only the main current one survived the eruption. Analysis suggests the eruption took place from a vent in the southern part of the caldera of Furnas volcano. with seismic activity caused extensive damage destroying almost all buildings within a 10 km radius and probably triggered landslides on the southern coast. Throughout the course of the eruption more than six discrete ash layers were generated by magmatic explosive activity. Isopleth maps suggest column heights of up to 14 km with ash falling up to 550 km away. Recent Activity During February of 2018 an earthquake swarm was reported in central Sao Miguel island. Dozens of mostly small quakes at shallow depths between 1-15 km in an area about 6-7 km west of Furnas volcano, were recorded some of which were felt by local inhabitants. It is unclear whether the earthquakes are volcanic in origin or not. If so, they could have been caused by a small magma intrusion at the lower crust and indicate an early sign of possible re-awakening of the volcanic system. Discussion Furnas is closely monitored and no eruption is indicated in the near future, yet there are so many different hazards associated with the area that it would make me feel uncomfortable living in an active caldera as people do.
  13. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mount Tsurumi and the Beppu hell springs Reason for Interest Some places are just unique and Beppu City falls into that category. A city with over 3000 hot springs that shrouds the city in hot mist in the early morning is an unusual sight. Bearing in mind that Mount Tsurumi Magma provides heating for the springs and lives in the same tectonic setting as Mount Aso this seems a risky place to find a city. Perhaps surprisingly the greatest risk here is from Tsunamis or landslides caused by earthquakes. Beppu hell springs The Japanese town of Beppu on the island of Kyushu is perpetually shrouded in steam thanks to almost 3,000 of hot spring vents that eject over 130,000 tons of scalding water on a daily basis. Only Yellowstone National Park in the US discharges more. Dubbed the Hells of Beppu due to the high temperatures they record, the hot springs remain relatively unknown outside of Japan. The hot springs in Beppu record high temperatures of water with some said to reach the boiling point of water. Some of the springs(hells) have become tourist attractions with the number of visitors frequenting the area can rise up to 60,000 people. Beppu Park is also popular at the center of beppu with flower gardens and hanami trees in cherry blossom at the right time of the year. Umi Jigoku or the Sea Hell is a beautiful cobalt blue color. The temperature of the pond is so hot that it stays at a rolling boil and can poach an egg. It has a large mass of bubbling aqua blue water, secondary orange coloured hells, lotus flower pond, foot onsen (bath). Oniishibou Jigoku or Shaven Head Hell, is a mud pool. The boiling temperatures of the water make mud bubbles at the surface. The pond is named for the resemblance of the mud bubbles to the hairless head of a Buddhist monk. Yama Jigoku or Mountain Hell was formed by a mud volcano that also made a small mountain with small ponds around it. Kamada Jigoku or Cooking Pot Hell is a group of several bowling springs. A statue of the devil is perceived to be the chef. As these ponds are cooler than the other springs, tourists can drink the water and enjoy snacks cooked in the pond. Oniyama Jigoku. The pond is known by Crocodile Hell as it is home to 100 crocodiles. The pond is also known as Demon Mountain Hell as the spring generates a lot of steam. The steam is said to be able to generate enough power to tug one and a half train cars! Shiraike Jigoku or White Pond Hell, is named for the white steam coming off the pond and blanketing the area. The waters are a milky white tinged with emerald from the sassolite minerals. Tatsumaki Jigoku or Spouting Hell, features a geyser that spouts every 30 minutes for about 10 minutes. The water can reach a height of 160 feet. hinoike Jigoku or Blood Pond Hell, is named for the distinctive red water of the pond from the water's high iron content. The water has antiseptic properties, and tourists can dip their toes downstream or purchase a mud paste. Kinryu Jigoku or Golden Dragon Hell is named for a dragon statue at the pond that looks as though it has come to life from steam rising from the pond coming out of it's nostrils. The rim of the pond also has a golden sheen. The Keicho Bungo earthquake During 1596 an earthquake with strength m7.3 occurred out in the Bay of Beppu. A recent high resolution shallow water profiling survey revealed recent activity of submarine fault which was newly found to fill a gap between two subaerial faults, the Asamigawa and the Funai faults running on the southern coast of Beppu Bay. Historical records suggest that this activity on the north-dipping normal fault corresponds to Keicho-Bungo earthquake. Core samples obtained from the both sides of the newly found submarine fault suggest repeated occurrence of this simultaneous rupturing with recurrence being approximately 460–1850 years. Records and modelling suggest that the tsunami height was over 8m and travelled many kilometers inland at low lying areas. In addition there were reports of the earthquake triggering landslides which created more tsunamis and damaged farms on the volcano. The Tectonic environment The Japanese archipelago consists of four main islands aligned north to south and surrounded by smaller islands. Kyushu is the southernmost of the four islands. It is located on the Eurasian Plate which is bordered to the southeast by the Philippine Sea Plate. Generally in Japan magma is believed to form when the Philippine Sea Plate is subducted beneath the Eurasian Plate. Unlike the rest of Japan, Kyushu is situated in an extensional region and for that reason a rift has developed running from east to west across the island. The Beppu Shimabara graben (rift) extends NE SW of the center of Kyushu Island with the Beppu geothermal field being situated within 30 km on the eastern flanks of Mount Garan and Mount Tsurumi. Earthquakes that have occurred in this graben shows that the cut off depth of the earthquakes increases with the distance from the Mount Tsurumi volcano, which is considered to reflect the temperature structure affected by a high-temperature magma body under the volcano. The earthquakes are probably triggered by the fluids migrated from the magma body into the brittle crust under active stretching. There is an active seismic cluster in the eastern flank of the volcano near the southern border fault of this graben which is an area of localized increases subsidence. The Volcano This volcano group consists of lava domes stretching 5 km north-south across the Beppu graben, which itself extends from east to west behind Beppu city. Tsurumi is at its southernmost end. The volcanoes in the group are composed of andesite and dacite (is between 57 and 63 wt %). Tsurumi is composed of deep lava flow deposits. A weak fumarole is located on the northern side of the summit of Tsurum, and very active fumaroles are in the crater of Garan, at the northern end of the volcano group. The alluvial fan at the east foot of the volcano group contains the Beppu Onsen group, and a particularly large number of boiling springs and fumaroles are distributed on the border between the fan-shaped north-south rim and the mountain land. On the northern side of the summit of mount tsurui are fumaroles and there is strong fumarole activity on mount garan. Beppu Ropeway goes up Mount Tsurumi, with an altitude of 1,375m and is Kyushu's largest ropeway. It has a capacity of 101 passengers, and it only takes about 10 minutes to reach the top. Rising above Mount Tsurumi you can enjoy the cherry blossoms in spring, the Miyama Kirishima flowers that are only seen in the high mountains of Kyushu, the silver frost spreading across the land in winter, and the autumn colours in autumn. Past Eruptions There was a 200 AD eruption was large (VEI=4), explosive, and generated pyroclastic flows. During 771 and 867 there was Tephra fall and a Lahar from Garandake. The Garan eruption resulted in lots of fish deaths in the local rivers. Recent Activity In 1949 Many white fumes approximately 10 m high and with temperatures of 95 °C were detected in an oval-shaped area at an elevation of 1100 m, approximately 500 m northwest of the summit of Tsurumi. In 1974 Fumes more fumes detected at the same location as 1949 but rising to over 100m High. In 1995 A mud volcano was formed at a former silica excavation site on Garan. The oval mud volcano grew until it was approximately 10m across and 4m deep. In 1999 was an increase in earthquakes with hypocenter approximately 3km east of the summit of Tsurumi, with a depth of roughly 5 km. Since the 2011 off the Pacific coast of Tohoku Earthquake earthquake activity has increased between roughly 4 and 5 km below the western and eastern sides of the summit of Tsurumi. Discussion Realistically the volcanic or earthquake risks here are pretty low, but to call it dormant would also be a stretch. I guess it is just so complex and unusual that it warrants more attention.
  14. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Nisyros Reason for Interest An secret Greek island with rising fumarole temperatures and tectonic activity raises my curiosity.It is not a highly populated Island or much of a tourist destination yet is steeped in human history along with a history of earthquakes and past minor eruptions. I guess being off the beaten track makes it worthy in mind of being more widely talked about. The setting Nisyros is one of the most beautiful Aegean islands, still untouched by the tourism growth. It is part of the Dodecanese group of islands, situated between Kos and Tilos. The island extends over a surface of 41 km and its coastline is 28 km long. Its coasts are generally rocky or pebbled, but there are also a few sandy beaches (mainly in the northeastern part). Some sea temperatures around me can reach 60 degrees Celsius due to hot spring waters. Nisyros can experience the Meltemi Etesian wind through June to August. This is most obvious on the eastern and western flanks of the volcano (known locally as Polyvotis), where trees are bent towards the south from the force of the winds. The wind may be especially strong on the island due to jet effects as it passes over Kos. In many parts of Nisyros you can find hot springs but the only ones that have been subject to economic exploitation are those of Paloi and Mandraki. The use of the waters of Mandraki began in 1870 by Nicholas Apostolidis. After he was cured, he built two rooms and three baths, which he donated to the community of Mandraki. The island is criss-crossed by a dense network of kalderimia, the traditional stone-paved mule-paths that used to link the settlements. Mandraki is the capital and main harbour where the houses are made of volcanic rock and insulated with pumice stone. The Monastery of Panagia Spiliani is the religious centre of the island. Located above the wild black beach at Mandraki, the largest part of the monastery is set within a cave. The main church is dedicated to the Assumption of the Virgin Mary, while the adjacent chapel celebrates Agios Charalambos. Picturesque Nikia clings to the rim of the caldera, and is said to be the island’s most beautiful village. With its elegant elliptical shape and cobblestone mosaic floor, Porta Square is the heart of Nikia and home to the stunning church, Agios Ioannis Theologos, which has panoramic views into the volcanic craters from its bell tower. Nikia is also home to the only volcanology museum in Greece, with fascinating displays about Nisyros and other Greek volcanoes. The Prophet Elias in Nikia is probably the most beautiful chapel in the Aegean and is located on a hill a bit outside the village of Nikia. A mountainous village Emporios on the northeast of Nisyros was destroyed in the 1933 earthquake, but is today regarded as the heart of the island. At the heyday of Emporios there were more than 3000 people living there and this was the commercial hub of the island, which is kind of hard to believe as it lies on top of a hill and quite a distance from the port were all the goods are coming from. Built on layers of lava, ash and pumice, this traditional village is home to the medieval castle of Pantoniki and the Taxiarhis Church with its rich frescoes. There's even a cave that's used as a natural sauna. Houses have been built in and around the castle, on top of each other, and in a jumble along the hill, but only 25 or so are still lived in. Paloi the youngest village is the other coastal town with a sailing marina and was the destination for refugees from Emporios.The sandy beach of Paloi is shaded by tamarisk trees and popular with local children. On Nisyros you will get to taste traditional dishes like pitia (chickpea nuggets),kapamas (stuffed goat) and of course fresh fish. To accompany your meal you can have a refreshing soumada (almond-based soft drink), kanelada (cinnamon-based soft drink) or koukouzina (high alcoholic drink). The Tectonic environment The island belongs to the Hellenic Orogenic Arc, which is formed along the convergent plate boundary of the northwards subducting African plate underneath the active margin of the European plate. As a result of subduction and extension, significant magmatic activity occurred in the past. The subducting African plate’s rocks are dehydrating and as a result of the high temperatures that the plate encounters as it descends deeper the African plate remnants are melting. The melt that is produced has a lower density than the surrounding rocks, and as a result, ascends toward the surface, penetrating the overlaying Eurasian plate rocks. Nisyros developed within a graben (rift) formed by the localized twisting and stretching of the plate causing the seabed to sink and the melt from below to percolate through. The Volcano The small round island of Nisyros is one of the more active but less known volcanoes in Greece. It is located south of the popular beach holiday island of Kos. The last eruption of Nisyros were phreatic explosions in 1881-87. They left a moonscape with colorful craters and very active fumaroles. A Magma chamber below Nisyros is only 3-4 km deep and still rising up. Since 2000 when the Nisyros research program of the GEOWARN-Team started, the temperatures of the fumaroles have been changing from 98 C to 103 C in 2004. There was also a high tectonic (earthquakes) activity in the last years and so a program to prevent volcanic hazards is still ongoing. The biggest and most impressive crater on the island of Nisyros is called Stefanos, and is the center of attention for most tourists as it is one of the biggest and best preserved hydrothermal volcanoes in the world. The crater is ellipsoidal in shape its longest axe being 330 meters in length while its shortest is 260 meters. Its walls culminate at 30 meters while it is estimated to be 3.000 to 4.000 years old. The island has a 3-to-4 kilometre wide caldera, and was formed within the past 150,000 years, with three separate eruptive stages. This caldera is divided into two parts: the NE one (Lakki), featuring lush vegetation, and the SW one (Ramos) which hosts intense steam emissions. Past Eruptions It is believed that the volcano erupted in 1442. In 1872 an eruption ocured accompanied by several earthquakes, the volcano emitted red and yellow flames and ashes covered the ground of Rammos. During the eruption of 1873, a 6 to 7 meters crater was formed and ash and mud spewed out. The ground of Lakkoi and Rammos were covered with hot salty water that came out of the crater. The most recent eruption was in 1888 which formed a cylindrical aqueduct of volcanic elements with a minimum diameter of 25 meters. They left a moonscape with colorful craters and very active fumaroles. Recent Activity ter a repose time of several years, intense, shallow seismic activity started at the end of 1995 in the volcanic region of Nisyros island. By the end of October 1997, hundreds of shocks had been recorded, the largest one being that of 27 August 1997. A focal migration was found from a region situated off of the NW coast of Nisyros towards the central caldera. This was interpreted as the brittle response of the volcanic edifice to an inflation of a magma chamber located to the NW of the island. In January 2003, the crater of Nisyros was declared off-limits to visitors. Temperatures in the hydrothermal system had increased from 210°C to 315°C, there was continuous microseismic activity as well as changes on the surface. The ban on visitors was prompted by a crack on the volcano that almost tripled in length over one year (but was apparently not of volcanic origin). Discussion The historical hydrothermal eruptions, the present chemical changes of the fumaroles and the physical phenomena affecting Nisyros could represent long-term precursors of a new period of volcanic unrest, which might culminate in a magmatic eruptive phase. However the type of earthquake swarms so far are thought to be typical of calderas that do not culminate in a volcanic eruption.
  15. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mount Baker Reason for Interest Thought to be the second most active volcano in the continental United states after Mount St Helens then this volcano warrants some attention. Recent activity is thought to be mainly Hydrothermal with little suggestion of any coming eruption however there are potential hazards from earthquake activity or even minor eruptions. Despite being in view of both Vancouver and Seattle the threat to major cities would be mainly around infrastructure and travel. The Setting Mount Baker sits just below the Canadian border in the north west of the United States and lies within the beautiful Mount Baker Snoqualmie National Forest spans 1.7 million acres on the western slopes of the Cascade Range in Washington. The forest includes glacier-covered peaks, spectacular mountain meadows and old-growth temperate rainforests. The verdant valleys and forested mountains host an array of amazing wildlife including salmon, northern spotted owls, fishers, elk and more. The Mount Baker Snoqualmie National Forest is one of the most visited National Forests in the country with over 2.5 million people visiting each year. Vegetative cover is typical of the west slopes of the Cascades including western redcedar, coast Douglas-fir, noble fir, Pacific silver fir, subalpine fir, western hemlock and mountain hemlock, and at higher elevations, alpine meadows. Animals include mountain goats and hoary marmots. On the slopes is the town of concrete named after the Superior Portland Cement Company plant was built there. The Henry Thompson Bridge at the center of the town was the longest single-span reinforced concrete bridge in the world when it was built. Downstream is the city of Mount Vernon named after George Washington Estate in Virginia. Since this city was founded, the downtown area of Mount Vernon bordering the Skagit River has been plagued by flooding, especially during times of heavy rain. The Tectonic environment The last of the Farallon Plate is now made of three small fragments The Gorda, Juan de Fuca and Explorer plates. The Explorer Plate broke off from the Juan de Fuca plate between 5 and 7 million years ago. As it did, the Cascade Arc resumed and the modern Cascade and Olympic Mountains began to rise. When the Cascade Arc volcanicity resumed 4 to 5 million years ago after reorganization of the Explorer Plate, there were some changes along the northern end. Where the northern end of the arc originally extended due north from the modern-day location of Glacier Peak into the Chilliwack Batholith and the Pemberton Belt in Canada, it now headed northwest into the Mount Baker and the Garibaldi area. This apparently reflects a steepening of the subduction zone on the northern end of the Juan De Fuca Plate. At the same time, the Juan De Fuca Plate assumed a more easterly-directed sense of motion relative to the continent. Mount Baker is the most recent descendent in a long line of volcanoes tracing their ancestry back into the Oligocene Chilliwack Batholith. The Volcano Snow and ice-covered Mount Baker also known as Koma Kulshan (white Steep Mountain) located in northern Washington is the third tallest mountain in the state at 10,781 feet. Located in the Mount Baker Wilderness it is visible from Vancouver in British Columbia and to the south from Seattle. Mount Baker is a stratovolcano constructed above the east flank of an older eroded volcano the remnants of which are the Black Buttes craggy peaks west of Baker and SW of the early Kulshan caldera. The Schreibers Meadow cinder cone on the SE flank erupted about 9800 years ago. All other historic activity within the past 10,000 years seem to have taken place on the summit vent. A major magmatic eruption at Mount Baker occurred about 6500 years ago. The volume of ice on Mount Baker is greater than that of all the other Cascades volcanoes except Mount Rainier combined. At mount Baker continued elevated gas and heat flux from fumaroles in sherman crater indicate the presence of a degassing magma reservoir. The volcano was named for Lt. Joseph Baker, a member of the British expedition led by Captain George Vancouver that explored the waters of what’s now Washington and British Columbia in 1792. Ice filled Carmelo Crater is under the summit ice dome and is the source for the last cone-building eruptions. The highest point of Mount Baker, Grant Peak, is on the exposed southeast rim of Carmelo Crater. Carmelo Crater is deeply dissected on its south side by the younger Sherman Crater. This crater is south of the summit, and its ice-covered floor is 1,000 ft (300 m) below the summit ice dome. Hazard risks If a summit magmatic eruption occurred then all drainages around the volcano will be susceptible to non cohesive debris flows that form as the result of hot volcanic material, melting snow and ice. These debris flows will likely transform downstream into watery debris flows or floods. Of special concern is a debris flow entering Baker Lake and displacing enough water to either overtop Upper Baker Dam or cause failure of the dam. Either scenario would have consequences for the stability of Baker Dam. If Baker Dam should fail, the resulting debris flow or flood would most likely affect the entire Skagit flood plain to Puget Sound. Debris avalanches could occur without an accompanying eruption from the Sherman Crater due to earthquakes or hydrothermal activity. Because winds are dominantly from the west, it is likely that any tephra that is produced will be carried to the east. Even minor amounts of Ash can affect the performance of aircraft, communications, damage machinery, close transport routes, block car air filters and electricity supplies. An under appreciated risk is the hazard of forest fires which happened during previous eruptions. Today lake baker is bounded by two hydro electric dams which modelling shows that if they failed would increase flood water levels in the city of Burlington by 12 feet which might be enough to break the protective levees. In the event of an eruption and lahars then Transportation routes like the I5 into Vancouver could be damaged, along with closure of local airports, local power outages and not least rural areas the size of New York could be flooded. Past Eruptions The largest eruption in the history of the Mount Baker volcanic field occurred more than 50 km3 of rhyodacite magma exploded from a shallow magma storage region and filled the caldera and surrounding valleys. That amount of material would cover the island of Manhattan to the greater than the height of the empire state building. As the eruption progressed, the rock on top of the magma storage region collapsed forming the depression of the Kulshan caldera. For 160,000 years after the caldera-forming event, dike-fed eruptions produced lava domes and lava flows inside the Kulshan caldera. Additionally, at least two eruptions occurred about 3 to 4 km (1.9 to 2.5 mi) west of the caldera at Chowder Ridge and Dobbs Cleaver. Near Lava Divide and Parke Butte, are the signs of the initial shift of volcanic activity to the southwest, away from Kulshan. Located about halfway between present-day Mount Baker's summit and the western Kulshan caldera boundary. Near the southern foot of modern Mount Baker, a basaltic lava flow near Park Butte erupted around 716 ka. Today there is a lookout for hikers atop Park Butte, which is a former fire lookout. Recent Activity Mt. Baker erupted in 1843. This eruption resulted in the deaths of many fish in the Baker River, a large forest fire, and the dropping of volcanic ash.Explorers reported a widespread layer of newly fallen rock fragments "like a snowfall" and that the forest was "on fire for miles around". Rivers south of the volcano were reportedly clogged with ash, and Native Americans reported that many salmon perished. A short time later, two collapses of the east side of Sherman Crater produced two lahars, the first and larger of which flowed into the natural Baker Lake, increasing its level by at least 10 feet (3.0 m). In Spring 1975, scientists measured a ten-fold increase in thermal activity and detected magmatic gases, increasing concern that an eruption could occur. The steam eruptions in and of themselves were not really a threat but what was a threat was the rock on the east rim of the crater, where there’s an opening and the Boulder Glacier comes out of the crater and goes down the side of the mountain. The fear was that a big chunk of that rim of the crater might slide down the mountain and into Baker Lake. A landslide that big could potentially create a wave that would wipe out anything along the shores of Baker Lake and even damage or possibly destroy the Upper Baker Dam. Such an event would result in a large volume of water rushing into the Lake Shannon reservoir and potentially cause a surge of water over, or failure of, the Lower Baker Dam. Failure of the Lower Baker Dam would result in catastrophic flooding down the Skagit River with little to no warning. This was an especially worrying scenario for the town of Concrete which lies at the foot of the Lower Baker Dam. The data collected suggests that magma may have intruded beneath the volcano in 1975, but it did not have enough energy to erupt. The magma stalled, likely in the form of a dike, and has been cooling since. By the fall of 1975, melting of Sherman Crater glacier resulted in a snow-free area three times larger than typical summer exposure and revealed a shallow lake and previously unknown fumaroles. Between June 16 and August 22, 2009, a swarm of least 39 low-frequency (LF) seismic events occurred at shallow depths beneath Mount Baker, a Cascade Range composite stratovolcano located in northern Washington. The LF events had several characteristics similar to classic volcanic low-frequency events. Analysis of Mount Baker earthquake events found other examples of shallow LF events occurring in 2005, 2006, and 2007, and similar events have been recorded in 2010-2012, all during the months of May-October. Based on several lines of evidence, including their seasonal occurrence, scientists believe that these events are occurring along the base of a glacier at Mount Baker, most likely the Easton or Deming glaciers (where most of the events locate), and are not related to volcanic activity. In contrast to the virtual absence of shallow earthquakes at Mount Baker, at depth it has the highest concentration of so-called Deep Long-Period events of any volcano in the Washington and Oregon Cascades. A 2011 study cataloged DLP events in the Washington and Oregon Cascades, and found that, since 1980, more DLP events have been located in the vicinity of Mount Baker than at the rest of the Cascade volcanoes combined. These events are thought to be related to movement of fluids or magma. Discussion On the face of it this is a remote volcano with very little suggestion of activity yet there are some potential hazards associated with it. I guess my interest is the contrast between the stunning scenery and sleepy towns against the slumbering giant that could throw a curve ball.
  16. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Tamagawa hot springs Reason for Interest Not all Volcanoes are big or threaten big eruptions, but some have anomalies which are curious and may represent threats which are not obvious. Volcanoes which produce acidic radioactive hot springs and have mud eruptions could leach dangerous contaminates into rivers with unknown consequences. This will be another short post due to the shortage of information. The Hot Spring Tamagawa Hot Spring located at the base of Mount Akita Yakeyama is a hot springs in Japan with the largest discharge from a single source (9,000 litres per minute) and also boasting the most acidic spring water Japan. Temperatures reach 98 Degrees and due to deposits of radioactive hokutolite near the spring, the water is also slightly radioactive. Tamagawa Onsen has just a single ryokan with a large number of simple rooms and a public bath, where guests can either stay overnight or use the bath on a day visit. More than other Japanese hot spring resorts, Tamagawa Onsen attracts a large percentage of guests who primarily come for health reasons. The Volcano Akita Yakeyama is a small stratovolcano, approximately 7km in diameter, and with a relative height of approximately 700m. A summit crater 600m in diameter is located at the summit area, and the Yakeyama summit is located on it south western rim. The volcano has two lava domes. A flank volcano, Tsugamori, is located on the eastside of the main volcanic edifice, discharging lava to the east. Another flank volcano, Kuroishimori, is located on the other side of the main volcanic edifice. Tamagawa Onsen which is located at the western foot of the volcano. Eruption history The Tsugamori western lava dome was formed at the summit approximately 2,500 years go. This was followed by, at least, three phreatic eruptions which occurred around the summit, in the 14th to 15th century, 15th to 17th century, and after the 17th century. Several small phreatic eruptions whose deposits have not been preserved are considered to have occurred within the historical period, but details of them are not known. Recent activity During May 1997 there was a land slide and Phreatic Eruption. The land slide reached the top of the hot spring. On the following day there was a large collapse occurred on the same flank. Steam discharge and ash fall were observed at the collapse site. In August 1997 there was a small phreatic eruption in the southeast of Karanuma, near the summit. Mountain climbers witnessed a volcanic plume. Muddy volcanic ash was sprayed up to 300m south of Karanuma. Discussion I am not convinced of any real threat from this environment but it is sufficiently odd to warrant a few words.
  17. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Marsili SeaMount The Reason for Interest When we think about very large volcanoes in Europe we tend to think of Mount Etna yet there are some even larger little known submerged volcanoes. If one of those Volcanoes is a rather crumbling volcano which could have a flank collapse and produce a tsunami in the Mediterranean then this elevates the volcano to a more interesting one. This will be a slightly shorter post due to limited information being available. The Setting The African plate is on a collision course with the European Plate creating a subduction zone in the western Mediterranean. Over time Africa has moved so far north that almost all of the heavier oceanic crust between the continents has been subducted underneath the European plate. With Africa’s continental crust just not being heavy enough to subduct anymore the subduction has slowed and in some areas reversed. What we are left with at present is a result of very complex subduction systems and rifting processes. In the SE part of the Tyrrhenian Sea the bending and stretching crust produced several basins. The rapid sinking of the Marsili Basin due to stretching was accompanied by rigorous magmatic activity from numerous volcanoes. In the Marsili basin reside at least two active submarine volcanoes the Marsili and Palinuro Seamounts. The older Palinuro Seamounts topology in its western part suggests a caldera-forming gravitational collapse event of the edifice has occurred. The Volcano This seamount was discovered during the 1920s and named after an Italian geologist, Luigi Ferdinando Marsili. Extensive studies have been carried out since 2005 when the Italian National Research Council started a vulcanology research program on the site. It is the largest volcanic edifice in the Tyrrhenian Sea, and it can also be ranked as the largest in Europe. The huge massif is about 55 km long and 30 km wide. The foot of the volcano is at a depth of 3000 m and it rises to some 500 m below the water surface. Marsili formed by passive magma ascent along existing fractures caused by early spreading activity. Analyses of Marsili basalts suggest the presence of a still active magma reservoir roughly 2.5 km below the summit of the volcano. Various seismographs positioned on the volcano have detected continuous shallow volcano-tectonic seismic activity. Recent Activity The most recent known eruptions of Marsili date back to an age between 7,000 and 2,000 years ago. These were events with a low VEI, occurring particularly in the central sector of the massif between 800 and 1000 m of depth. In the case of a submarine eruption at depths of 500-1000 meters, the only signs on the surface would be pumice floaters, a colored stain and spots of boiling water due to degassing. Discussion The volcano is mechanically stabilized by a series of fractures filled with compact lava rock forming containment walls. Research vessels found evidence of many small, localized landslide scars along its flanks. Such landslides reducing the flanks are very common in submarine structures but might have reduced the thickness of those containing walls. It is thought that an inflation from the ascent of a quantity of magma could seriously destabilize whole sectors of the volcano. Tsunamis, caused by submarine landslides could extend to all the Tyrrhenian coasts including the shores of Campania, Calabria and Sicily. Evidence suggests that similar Tsunamis have happened several times in the past. Whilst the threat is clear we should be careful not to over emphasize it.
  18. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mount Gede Reason for Interest Three major cities, Cianjur, Sukabumi and Bogor, are located near to Mount Gede. With the growth of Greater Jakarta and those 3 cities, dense suburban growth has engulfed the fringes of the volcano, home to roughly 4 million people. The Volcano is thought to produce large eruptions in the past and with the huge populations nearby the potential for severe destruction is significant if a large eruption occured. It should be pointed out that most recent eruptions have been at most VEI2 smaller eruptions. What has piqued my interest is the fact that rock crystals analysis of magma suggests that magma must have risen through roughly 35 kilometers of crust in just months during past eruptions. The Setting Mount Gede or Gunung Gede (Big Mountain in Sundanese) is a stratovolcano in West Java, Indonesia. The western side of the volcano is bordered by Pangrango, which is an extinct volcano. The volcano is within the conservation area Mount Gede Pangrango National Park. The park contains fast flowing rivers, waterfalls, lakes, montane forest, elfin woodland, subalpine grassland, and unique mountain flora and fauna including an edelweiss meadow. By international standards this is a small conservation area yet it is one of the most visited in the world with an estimated 20-30 million tourists flocked to the dual volcano site. West Java is a province of Indonesia on the western part of the island of Java, with its provincial capital in Bandung. It is bordered by Jakarta to the west, the Java Sea to the north, the province of Central Java to the east and the Indian Ocean to the south. The province is the native homeland of the Sundanese people, the second-largest ethnic group in Indonesia after the Javanese.IT has rich and fertile volcanic soil with traditional dry rice, coffee, tea, and quinine being cultivated. The mountains and uplands have a dense growth of tropical rainforests comprising teak, eucalyptus, rhododendron, juniper, banyan, oak, ash, maple, and ironwood. The park is also rich in wildlife and birds such as the Java Gibbon, Javan langur, leopards, pangolin, wild boars, Javan hawk-eagle and the Javan scops owl. The wet season is from November through to April with the driest months being July and August. Humidity is usually very high and temperatures are fairly consistent through out the year at around 28 degrees Centigrade. Temperatures at the volcano summits can dip below 10 degrees Centigrade and get occasional frosts. The Tectonic environment The volcano belongs to the Sunda arc which is associated with the subduction of the Indo-Australian plate beneath the Eurasian plate. Magma originates from partial melting of the mantle wedge driven by the fluids from subducting slab. Large geothermal fields are found in West Java compared to ones in Central and East Java. Rock Crystal Analysis From the rocks released by that 4000-year-old eruption Costa and his colleagues at the Center for Volcanology and Geological Hazard Mitigation of Indonesia in Bandung were able to glean some crucial clues about Gede's behavior. The clues were locked in crystals, most smaller than lentils, embedded in the rocks. Each crystal grew in a soup of magma deep underground, accreting layers that bore witness to the events that preceded the eruption, and most importantly how fast they unfolded. These crystal clocks told Costa's team that Gede's 4000-year-old eruption came roughly 4 weeks after the injection of a fresh batch of magma beneath the volcano. Crystals from four more ancient eruptions gave similar answers. The Volcano Gede volcano is also known as Gedeh, Ageung or Agung. There are 7 summit craters - Gumuruh, Gedeh, Sela, Ratu, Lanang, Wadon and Baru. Currently the most active craters are Lanang and Wadon.The edifice of the volcano consists of 3 major parts having different ages. The main stratocone (called Gumuruh) with 1.8-km-wide summit caldera is the oldest part. The Intra caldera cone (Gede proper) with 900m wide summit crater and the Intra crater infill composed of a lava dome with 3 small explosive craters on its top being the youngest. On the slopes can be found the Telaga Biru/Blue lake with blue green algae surrounded by sub-montane to montane vegetation.This is a good place to watch the Sunda Cuckoo-shrike and Sunda Thrush to come to drink.A little further up the slope is the Cibeureum Waterfall consisting of three waterfalls, formed from the Cikundul, Cidendeng, and Cibeureum rivers the highest of which is 50 meters high. A red moss, endemic to the mountains of West Java, can be seen growing on the rocky outcrops at the waterfalls and the bats seen flying around come from the nearby bat cave of Gua Lalay. A little higher are the hot Springs/Air Panas with water temperature as high as 75°C which contain an algae which is remarkably adapted both to hot water and high sulphur levels. The hot springs are a good place to see the Javan Cochoa and Blue-rumped Trogon birds. At the summit are three semi-active craters grouped together: Lanang (male), Ratu (queen) and Wadon (female). Acid rocks, sulfur rich gas emissions and an inhospitable climate all make for extreme conditions. In response, a fascinating plant community has developed including two rare species of rhododendron. The famous naturalist Alfred Russel Wallace was so impressed by the areas beauty and uniqueness that he wrote, “by far the most interesting incident in my visit to Java was a trip to the summits of the Pangrango and Gede mountains”. The trail on the south-eastern slopes was found by Sir Thomas Raffles in 1811 which passes through some interesting and beautiful landscapes like Alun-alun Suryakencana the highland meadow covered with edelweiss flowers. Past Eruptions During the last few centuries there have been mainly small explosive eruptions of short duration. The largest eruptions were in 1840, and January 1948. The most recent eruption was on 13th March 1957 when following a roar from the volcano an ash plume reached 3km high above the volcano. The SE avalanche deposit from an earlier eruption covers more than 250 km2 on the lower south-eastern flank of the volcano in Cianjur region. It traveled at least 35 km, and had volume of no less than 10 km3 and would be within reach of certain cities today. Recent Activity 1991 Earthquake Swarm Earthquake swarms occurred at Gede volcano in 1991. On 29th April there were 100 earthquakes recorded, compared to the background level of 10-15 per day. On 1st May over 40 earthquakes were measured. Seismicity returned to normal after this and there were no changes to surface activity at the volcano. 1997 Earthquakes Earthquakes were measured at Gede volcano in August 1997. Volcanic earthquakes were concentrated in vertically elongated zone beneath the summit crater. The depth of hypocenter ranged from 2 –8 km below sea level. During the observations, A-type earthquakes with clear P and S-waves were observed at Gede volcano suggesting magma movement. Small volumes of erupted material suggests that the likelihood of future large volume eruption of the volcano is low with the strongest eruptions of the volcano thought to be in the VEI3–VEI4 range. The volcanic edifice of Gede is not exceptionally high or steep and the hydrothermal weakening of the rocks on the upper slopes appears to be of limited extent. Thus, large-scale gravitational collapse of the edifice is of low probability. However, a remnant of the NNE crater rim (Rock Sela) is gravitationally unstable and could collapse during the next eruption or large earthquake. Discussion Perhaps It is the large populations nearby that concern me or the propensity to erupt very quickly after a magma injection that concerns me. All evidence suggests eruptions are not likely to be large yet there is a sense of unpredictabilty and regularity of earthquake swarms that niggles. I am also not convinced that the the myth that the spirits of Eyang Suryakencana and Prabu Siliwangi will manage to stop eruptions. Then again perhaps my interest is why some hikers on the volcano think it is a good idea to take nude selfies.
  19. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Baru Reason for Interest Volcano Baru is a volcano with a history of explosive eruptions. It has the town of Volcan within reach of pyroclastic flows and the town of Boquete within reach of lahars. It has had recent swarms of earthquake activity and warrants close monitoring. It has been hypothesized that Volcán Barú experienced an eruption with estimates of ejected material ranging up to to 100 km3. Debris-avalanche deposits and lahars extend as much as 90 km away from the collapsed edifice, reaching the Pacific Ocean. What really piques my interest in the complicated tectonic environment or maybe it is the shangri-La rainbow town of Boquete. The Setting Barú volcano (also called Volcán de Chiriqui) is an active volcano 35 km east of the border to Costa Rica in the Talamanca Range of western in Panama. The complex, mainly andesitic stratovolcano is Panama´s highest peak and the forested volcano summit hosts many communication towers. The volcano slopes are known as the bread basket of my country and The highlands of Chiriqui on my slopes produce some of the most unique coffees in the world. The volcano towers above the small town of Boquete nestled in the cool highlands of the western Panama Chiriqui province. Boquete is described as a Shangri-La of tumbling streams, mountains clad in rain forest, abundant in orange groves and coffee plantations, with a picture-postcard town chockablock with flower gardens. With its cooler, fresher climate to the rest of Panama, it’s known as ‘The Valley of Eternal Spring’. It’s home to Panama’s most famous coffee region, plus a large number of US retiree expats. To residents of Boquete Panama, frequent rainbows are the product of the bajareque, a delicate drizzle that sometimes accompanies the north winds that blow down from the mountains. The rainbows arch, often in multiples, over the Valley of Flowers and Eternal Spring, aptly named due to the town’s vast array of exotic flora and its balmy weather that rarely registers above 80 or below 70 degrees Fahrenheit. Rock climbing is now one of the fastest-growing sports in the region. very year in January, the district of Boquete receives about 100,000 visitors who come to this region to stroll though the many pavilions of the famous Flower and Coffee Fair. Just outside Boquete town is Bambuda Castle the only castle in Panama. Perhaps the only thing that differentiates the seasons is the rainfall that occurs during the summer (roughly May through October) and ceases during the winter months (November through April). Commonly seen species in the area are the famous Quetzales, Black Guan, Black-thighed Grosbeak, Black and White Hawk-eagle, Toucans , Tanigers along with jaguars, pumas, ocelots, jaguarundis, and margay. You may also find the mischievous coatimundi, armadillos, tapir, sloths & monkeys. The Tectonic environment Volcán Barú lies along a complex plate boundary inboard of the Panama Triple Junction located in southern Central America, near the border with Panama and Costa Rica. The Panama Triple Junction (Cocos-Nazca-Caribbean) represents the point that abruptly separates the thick and rapidly subducting Cocos plate to the northwest from the thin and obliquely subducting Nazca plate to the southeast along the Central American convergent margin. The Cocos plate, to the northwest of the triple junction, subducts rapidly under the Caribbean plate and Panama microplate and exhibits significant changes in character along strike. The Cocos plate systematically decreases in dip laterally from a steep slab in the northwest outboard of Nicaragua, to an almost horizontal slab in southern Costa Rica and Northern Panama. The Nazca plate slab, in contrast to the adjacent Cocos plate, is likely steeper, contains thinner crust, converges at a much slower rate and subducts at a highly oblique angle. The large limestone contribution at Volcan Baru may reflect the large contribution of pelagic carbonates to the slab flux. In the Volcan Baru region there is the edge of the shallow subducted Cocos plate and a combination of extension and steeper subducted Nazca Plate. An extremely complicated and unusual tectonic environment. The Volcano Its summit, 3,374 m altitude, towers about 2,000 m above populated valleys to the west and about 2,400 m above those to the east. More than 10,000 people live in areas immediately adjacent to the volcano, where the hazards from future eruptions are greatest. The heavily populated Pacific coastal plain, crossed by the Pan-American Highway, lies 30 km to the south. Volcán Barú has been built by numerous eruptions dating back several hundred thousand years. The volcano is notable for its young, large andesitic to dacitic dome complex nested within a horseshoe-shaped amphitheater carved into the older part of the volcanic edifice. Eruptions of the past few thousand years have been from vents on the summit dome. A large 6-km-wide summit caldera breached to the west was formed by a large volcanic landslide, which created a massive debris-avalanche deposit about 9,000 years ago that extends onto the Pacific coastal plain, largely overlying a late-Pleistocene avalanche deposit. Post-collapse eruptions have constructed lava domes inside the caldera that have grown to a height exceeding that of the caldera rim. Prehistoric eruptions of Volcán Barú have repeatedly spread tephra blankets more than 100 km downwind and deposited thicknesses of 10 to 20 cm at distances 10 to 15 km downwind. Pyroclastic flows have been common during eruptions of Volcán Barú. Block-and-ash flows of the past 1,600 years have descended westward from the summit area toward and through the present-day town of Volcán. In 2008 the US geological survey highlighted a massive debris avalanche deposit described as the largest example in Central America. The volcano was declared a national preservation area called Volcán Barú National Park in 1976, with an area of 14,325 ha (35,400 acres). One of the park’s most popular trails is the Quetzals Trail, which runs between Cerro Punta and Boquete. The trail is 8 kilometers (5 miles) long and takes you through forests and meadows, and is crisscrossed by the Río Caldera. Another popular trail is to the lost Waterfalls Trail which takes you through lush cloud forest in search of three lost waterfalls. The cloud forests on the slopes can also be explored through the Boquete Tree Trek where 4.5 km of elevated zip lines let you explore the tree canopies. Past Eruptions The volcano has had four eruptive episodes during the past 1,600 years, including its most recent eruption about 400–500 years ago. Several other eruptions occurred in the prior 10,000 years. Several seismic swarms in the 20th century and a recent swarm in 2006 serve as reminders of a restless tectonic terrane. Recent Activity In 2006, an earthquake swarm was recorded near Volcan baru. This was not the first, researchers cite at least three other seismic events of the same nature, recorded in the recent past, 1930, 1965, 1985. Discussion Although it is thought unlikely the volcano will experience another collapse in the near future the risks of pyroclastic flows and lahars represent considerable threat to a significant population. Perhaps the biggest under appreciated risk is ash fall which could decimate agriculture and infrastructure.
  20. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Mount Hallasan (halla volcano) The Setting Mount Hallasan forms the backbone of Jeju Island in the Korea Strait to the south of mainland South Korea. Jeju is the largest island in the nation and is a very popular tourist destination amongst both Koreans and foreigners alike. Besides its incredible scenery and natural riches, the island’s enduring popularity is in part down to the fact that South Koreans weren’t permitted to travel abroad until the late 1980s. The island is home to 660,000 people but hosts 15,000,000 visitors per year.Jeju means ‘huge village across the sea,’ and has its own distinct culture, which is quite different from that of the mainland. Attractions include hello kitty Island, maze land and loveland (A bit naughty). Manjanggul Cave on the island is one of the largest and longest lava tube caves in the world measuring up to 30 meters high and 23 meters wide and stretches for a staggering nine kilometers. Cheonjeyeon Waterfall also known as the Pond of God originates from the ceiling of a cave and it comprises three sections. Around the subtropical falls you can find the rare and unique Solipnan reeds and Skeleton fork ferns. There are beaches around the entire island though the two most famous among tourist are Hyeopjae Beach and Jungmun Beach. Animals include the leopard cat, damselfish, the Jeju horse, green sea turtle, black-faced spoonbill and steller sea lion. It embraces four major ecosystems which are alpine coniferous forest, temperate broadleaf forest, warm temperate evergreen lucidophyll forest, and temperate grass land. There are occasional typhoons in summer and fall as well. Jeju is said to be home to 18,000 gods and goddesses. They are loved, feared, worshipped and placated at home and at village shrines, in the island’s shamanistic rituals and Buddhist temples, on mountain peaks and other sites sacred to Taoist belief. The Tectonic Environment Mt. Halla, or Hallasan, is considered to be a rare example of a shield volcano built on a continental tectonic plate. The island is located behind the Ryukyu Trench, the collisional boundary between the Eurasian plate and the Philippine plate. Gravity inversion indicates the island is developed above and along a ridge. The structure shows positive correlation with a high magnetic anomaly distribution that could indicate existence of volcanic rocks. One suggestion is that the high gravity anomaly belt is formed by folding/buckling process under compressional environment and which causes decrease of pressure beneath the lithosphere along the belt accelerating melting of basaltic magma. An alternative hypothesis is that the basaltic magma beneath the island could be caused by episodic lithospheric folding. The Volcano Hallasan is a shield volcano on Jeju Island in South Korea; it is the highest mountain in South Korea. Han represents the universe, and la means "pull". Both words mean that the mountain is high enough to pull the universe. Inside the crater is a lake called Baengnokdam meaning "white deer lake". It is formed by the collapse of the top of the ridge by the movement of magma underground. Depending on the season, the circumference of the lake is up to 2 kilometers with a depth up to about 100 meters. Eruptions of basalt and trachyte lava built the island above sea level, and it now reaches a height of 1,950 metres (6,398 ft). A large volcanic crater over 400 m (1,300 ft) in diameter tops the volcano. About 360 parasitic cones, or oreum in the Jeju dialect, are found on the volcano's flanks. Most of them are cinder cones and scoria cones, but there are also some lava domes and about 20 tuff rings near the coast and offshore, which were formed by underwater phreatic eruptions. Volcano Past Activity A report from the Korea Institute of Geoscience and Mineral Resources (KIGAM) surprised volcanologists by dating Jeju’s most recent volcanic eruption to 5,000 years ago. The research team, led by Jin-yeong Lee, radiocarbon dated carbonised wood (charcoal) below the basalt layer at Sangchang-ri, Seogwipo City, to 5,000 years old. The resulted in a designation of active which is disputed. While scientific evidence of volcanism on Jeju Island is proving difficult to confirm, one piece of historic evidence suggests that the island was active much more recently than 5,000 years ago. The “Dongguk Yeoji Seungram,” a Joseon Dynasty geography textbook includes this seemingly eye-witness account. “In June 1002 CE, a mountain arose in the middle of the sea. There were four giant holes at the top of the mountain, out of which red liquid flowed and soared, and thick smoke plumed for five days. All the red liquid hardened and became stone like roof tiles.” The account has long puzzled geologists, particularly as few clues were given as to the location of the eruption. The most fancied site had been Biyangdo, an island off of Jeju’s west coast, followed by the peaks of Songaksan and Dansan, both in the southwest of the province. Discussion This is not a volcano that would be on a top list of volcanoes to create major issues, yet it remains a sleeping enigma and should probably warrant more investigation. I bet most of the 15 million visitors to Jeju do not even know they are visiting a potentially active volcano. Just do not google Jeju loveland .
  21. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Cerro Machin Reason for Interest Cerro Machin is not the highest volcano in the region nor does it have a reputation, yet is one of the most dangerous volcanoes in Columbia with a history of repeated VEI5 eruptions. It has created lahars that ran for 100km and pyrocrastic flows that ran for 8km with over 20,000 people living within an 8km radius. What does pique my interest is the new muon background radiation experiment across the volcano which should be able to map some of the internals of the volcano. The Setting Cerro Machin is situated close to the equator in the department of Tolima in Columbia. There are no seasons, but it does enjoy a variety of different temperatures. It has snowy summits more than 5,000 meters high with below freezing temperatures, and hotter zones in wide valleys lower than 400 meters above sea level that reach temperatures hotter than 40 degrees Celsius. The Tolima department includes a mountainous region occupied by the Cordillera Central, a plain, that corresponds to the valleys of the rivers Magdalena and Saldaña and the region to the southeast which forms the western slope of the Cordillera Oriental. Famous regional dishes include the Tamal Tolimense which is a corn and yellow pea-based paste with pork, egg, chicken and vegetable filling, wrapped inside a plantain leaf. It is home to cotton top tamarins, sword billed hummingbirds, jaguars, capybara, Andean bears and glass frogs. The nearest city Ibagué features a cool (due to altitude) tropical rainforest climate and is known as The Musical Capital of Colombia and America. The city does experience noticeably drier conditions during the months of January and July but has no true dry season month, as all twelve months see on average more than 60 mm (2.4 in) of precipitation. Temperatures are relatively consistent throughout the course of the year in Ibagué, with average high temperatures of about 28 degrees Celsius and average low temperatures of about 18 degrees Celsius. The rapid expansion of coffee planting on the slopes above the city contributed to its growth, especially after 1890. The plain and the neighbouring valleys produce cacao, tobacco, rice, and sugarcane. The Tectonic Setting The Cerro Machin volcano tectonic province (SCVTP) is located on the axis of the central cordillera of Columbia. It is related to the subduction of the Nazca Plate underneath the South American Plate. The SCVTP host 10 polygenetic volcanoes including Cerro Machin. The Volcano The Cerro Machín a rhyolitic stratovolcano is located in the Central Cordillera of Colombia and is the lowest altitude volcano in Colombia (2750 m). Given the chemical composition, magnitude and extent of past eruptions, it is recognized as a explosive volcano with potential for damage to the local region for an extensive period. Cerro Machin volcano is located 150 km southwest of Bogota, 17 km west of Ibague, 30 km east of the city of Armenia on the eastern slopes of the Cordillera Central. Cerro Machin is in a warm temperate region with an mean temperature of 20°C, annual rainfall of 1150 mm, the average relative humidity is 85%, the dry and rainy seasons usually alternate during year. Cerro Machin has a 3km wide caldera breached to the south and contains three forested dacitic lava domes with fumarole activity and hot springs. Around the base of the domes to the south is a crescent shaped small lake. Columbia's national tree the wax palm covers much of the slopes up to the summit. In past eruptions pyroclastic flows traveled up to 40 km. The entire surface is covered by small tributaries of the Magdalena, the most important river of Colombia. It flows in a wide valley between the Cordillera Central and Eastern Colombian Andes. Muography or muon tomography is a technique which uses atmospheric muons to study geological structures. The most common tools for studying volcanoes is gravimetry and electrical tomography which lack spatial resolution. MuTe is a hybrid detector composed of two sub dectectors,a hodosco9e and water cherenkov detector. One prototype has been deployed to Cerro Machin dome to understand the volcano structure. Historic Eruptions The volcano has had 6 main eruptive cycles occurring over the last 10k years with the biggest eruption of Cerro Machin is thought to have occurred 3600 years ago. The last known eruption at Cerro Machín Volcano in the Central Cordillera of Colombia occurred ∼900 years BP and ended with the formation of a dacitic lava dome. It has been determined that during it’s previous eruptions it produced pyroclastic flows that traveled as far as 40 km from the volcano and mud flow deposits (lahars) up to 109 km distance from the volcano along the Coello and Magdalena rivers. Beyond this basic information there is very little information available about previous eruptions. Recent Activity In April 2004, a swarm of earthquakes occurred at Machín volcano. More than 60 earthquakes occurred daily, in comparison to the normal number of 1-10 quakes. An earthquake swarm occurred at Machín volcano on 9 November 2008. The increase in earthquakes was accompanied by an increase in fumarolic activity and there was damage to some buildings During December 2010 the number of earthquakes increased at Machin volcano. About 367 volcano tectonic earthquakes were recorded south and southwest of the main lava dome in the summit caldera in an area known as Moral, four to five kilometers deep. The largest event occurred at 5:22 pm on 1 January 2011, with a magnitude 2.3 at a depth of 3.3 km. The earthquake was felt by residents in vicinity of the volcano and in the town of Cajamarca (Tolima). An earthquake swarm occurred at Machín volcano on 9 November 2008. The increase in earthquakes was accompanied by an increase in fumarolic activity and there was damage to some buildings (USGS / GVP weekly reports). During 2020 the Servicio Geológico Colombiano recorded that the seismic activity continues at elevated levels. Most seismic activity has been associated with rock fracturing. The seismic station records earthquakes at 2.4-7.8 km depth beneath the south and southeast flank. On 6 May at 00:34 local time SGC detected an earthquake located 1.1 km southeast of the dome at 2.3 km depth. Discussion Cerro Machin would not immediately threaten major cities even though they are not far away but can have major impacts on trade and a significant number of people close by. In addition, a major transport route from Bogota to the Pacific (Route 50) could be affected. The major threat is to local agriculture particularly coffee bean growing. What surprises me is the general lack of information about one of the most dangerous volcanoes in Columbia despite quite technologically advanced monitoring.
  22. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcanic Island Pantelleria Reason for Interest Pantelleria is not a volcano likely to erupt yet some analysis suggests that any significant eruption could have a major impact on climate through sulfur dioxide emissions. This quiet beautiful Mediterranean island maybe a sleeping problem for humanity at some point in the distant future. The peculiarities of this volcano piques my curiosity. The Setting The island of Pantelleria (The Black pearl of the Med) lies between Sicily and Tunisia and covering 32 square miles. Originally named Bent-el-Riah ('daughter of the wind' in Arabic) for the year-round winds that buffet it, Pantelleria is characterized by jagged lava rock formations, steaming fumaroles and mud baths. The island's unique agricultural traditions, characterized by low-slung caper bushes, dwarf grapevines and olive trees laid out on terraces between dry stone walls. Little hamlets of stone domed houses called dammusi have been built down the centuries to resemble beetles with gardens of cactuses. The dammuso have two feet thick stone walls constructed from volcanic rock and the white domed roofs are natural forms of insulation and protection from the extremely high temperatures, so the rooms in the house are cool and the air is fresh constantly. Just inland from Pantelleria's north coast is Lago Specchio di Venere (Mirror of Venus) a blue volcanic warmed Lake. On the southern lakeshore are natural hot springs and mud baths with temperatures ranging from 40°C to 50°C. Volcanic mud from the lake has traditionally be used for a natural beauty treatment. There is also a natural hot sauna in a grotto on the side of Montagna Grande, the island’s highest peak (2,740ft).The island’s is famous for its deliciously sweet passito wine, made from Zibibbo grapes dried in the sun. Pantelleria has one of Geogio Armani's Summer vacationing homes Cala Gadir designed by native of Pantelleria Gabriella Giuntoli based on a number of dammusi. It has a outdoor living room terrace that looks out towards the sea, a swimming pool that appears like a natural pool and is close to the small harbour village of Gadir on the east coast of the island. Winters from December to January typically have temperatures around 12 Degrees Centigrade with frosts being extremely rare. Summer is from June to August with average temperatures around 25mDegees Centigrade. Temperatures can vary with wind direction with the "maestrale" (north-west wind) from Sardinia bringing cooler weather and the sirocco (southeast wind), which blowing from Africa bringing desert sand and temperatures which can reach 40 Degrees Centigrade. Despite winters being rainy the island receives about 20 inches of rain a year. It is home to gray and red herons, pink flamingos, cranes, black-winged stilts and storks, black kite, the peregrine falcon Eleonora's Falcon. You can find the Ilex, the Lentisk, the Cluster-pine, the red berries of the Strawberry-tree and the dark ones of the Myrtle, the Phillyrea, an evergreen shrub with a very strong scent, the Rue, one meter and a half high evergreen shrub, the Cistus with common pink flowers, the Erica Arborea e Multiflora with a upright shaft, the Oleaster and the smelling Rosemary. The Tectonic Setting The African plate is being subducted beneath the European plate under the Mediterranean Sea. When you delve into the details things are a little bit more complicated with micro plates and seperate blocks interacting with each other in different ways. The Adiatric Helenic slab is pulling away Northeast and the Adria plate has stopped moving north west due to the convergence in the alps. Pantelleria lies in the sicily channel which is a grabben (Valley) caused by rifting where the pelagian block was stretched by the differing movements of the micro plates to its north. More recent stretching is thought to be magma related through crustal thickness. The Volcano The island is roughly elliptical in shape measuring 13km by 8km. It is mountainous with dark coloured rocks with no beached. The most prominent feature is the volcanic mass of Montagna Grande occupying the center of the island and rising to over 800m in height. The top consists of a ridge with smaller volcanic cones like Monte Gibele on its slopes. Close to the north coast is the lake which is about 500m wide. Montagna Grande has been uplifted, although in a slightly unusual way. The eastern edge has been uplifted more than the western, rather like a trapdoor. Gareth Fabbro David Neave in their examination of Pantelleria report the magma type is Pantellerite a magma particularly rich in sodium and potassium, and poor in aluminium. It is a rare magma type, found only at a few volcanoes in other rifts, notably in the East African Rift. This very evolved Magma may have had 96% of the starting material removed through fractional crystallisation. The quick differentiation time at Pantelleria means that there is less chance for the Sulphur to escape, and hence more will be released all at once during an eruption. In total, they calculated that about 80-160 million tons of Sulphur would be released from a Green Tuff–sized eruption. Compare that to the 9 million tons of Sulphur from Pinatubo, an eruption almost three times the size. Pinatubo lead to a 0.4–0.5ºC drop in global temperatures, so imagine what an eruption of Pantelleria might do. Historic Eruptions Most of the information about Pantellerias eruption which occurred between 24 May 1890 and the end of November 1891, comes from a report by Annibale Riccò. The First warning of the eruption was the earthquakes of 24 and 25 May 1890 which had upset the inhabitants and the rapid uplift of the North East coast of the island by nearly a meter pushing the shoreline back. On October 14, 1891, a long sequence of earthquakes began in the town of Pantelleria lasting 10 days and forcing the inhabitants to flee inland. The climax of the crisis was reached on October 17 when the sea offshore became agitated by a strange boiling and a column of steam began to rise. Soon afterwards the first blasts were heard and there was no doubt an underwater volcanic eruption had begun. Many dead fish were sighted and the temperature of the water was warmer by a few degrees. The strangest thing observed was a long strip of floating blocks formed by a black spongy magma. A further oddity was the fact that these blocks, when they came out of the depths of the sea, emitted gas under pressure, which often made them literally fly 15-20 meters into the air, before falling back into the water. Closer observation from a naval ship showed blocks jumping into the air while others exploded throwing dangerous fragments. Once the gas was expelled, the blocks sank again and the smell of Sulphur was very strong. In the following days the explosions slowly ceased and no more blocks of lava were seen rising to the surface. The eruption had ended. After the eruption a period of deflation began with the source of deflation thought to be a Magma chamber 4 km below sea level. Radiocarbon dating of the alignments of encrusting organisms along the entire coast of the island two previous periods of uplift have occurred, 500 and 900 years ago. More recent investigations of the volcano show lava balloons were likely formed from the rapid cooling of extremely vesicular magma fragments as a result of a gas-rich frothy magma source. The exterior of these fragments hyper quenched forming a vesicular glassy shell that acted as an insulating layer preventing magmatic gas in its interior from escaping and thus allowing flotation. Current Activity The Island of Pantelleria is characterized by two contrasting processes. The First is a tilting process toward the SW related to strong uplift of the northeastern shoreline. The second is a marked deflationary process occurring in the area of the Cinque Denti caldera and centered in the area between Montagna Grande and Monte Gibele. The results of a seismic survey in 2006–2007, as well as the signals recorded by a permanent station in 2010–2014, show Pantelleria is characterized by a very low rate of seismicity. This would suggest there is no suggestion of volcanic activity in the near future. Discussion Any volcanic region that can produce ten times the amount of Sulphur emissions as Pinatubo released which dropped global temperatures half a degree is worth understanding. There is no suggestion of near future activity yet maybe some point in the future this idyllic island could change the world.
  23. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano Irazu Reason for Interest When a volcanologist describes a volcano as the highway to hell due to magma being able to rise from the mantle to eruption over a few short months then this peaks my interest. Knowing that it eruptions roughly every 20 years and has been quiet since 1994 makes this a volcano to be monitored closely especially since its close proximity to a major city. The Setting Volcano Irazu is part of the central mountain range in Costa Rica in Central America. Costa Rica borders with Nicaragua in the North and Panama in the South and lies between the Caribbean Sea and the Pacific ocean and can be split into four main geographical environments. Climate varies by elevation and proximity to the coast. The Caribbean lowlands are in the east of the country with a lot of Rain Forest Cover due to trade winds bringing hot and moist air and rain all year round. The much drier leeward Pacific lowlands lie to the west bordering the Pacific and consists of a surfers paradise of sandy beaches and mangroves. The Central Valley, including the capital city of San José and other major cities, have a more temperate climate constantly cooled by the coastal breeze. Costa Rica’s dry season runs from December through May and the rainy season from May to November. Major storms occasionally hit the Carribean coast between the months of September and February. The country’s average annual rainfall is roughly 100 inches, but some areas receive as much as 25 feet of precipitation. Costa Rica has one of the most diverse range of trees, animals and birds with around a quarter of its national territory protected by a system of conservation areas and national parks. From huge ficus trees, almond trees, cedar, balsa, heliconaias, pineapples, epiphytes to a large range of different orchids. Home to the jaguar ,agouties, sloths the elusive Margay, or the wonderful birds like the green or scarlet macaws. Around half of Costa Rica is cloaked in trees, with tropical rainforest, tropical dry forest and cloud forest. The country’s coastal waters are also home to a whole host of marine life, including sea turtles, manatees, swordfish, sharks and rays. The Tectonic environment The Volcanoes of Costa Rica take up much of the country, and exist due to the subduction of the Cocos plate underneath the Caribbean plate. Plate convergence rate increase southward along the subduction region rising to a maximum of 8.5cm per year in western Costa Rica. Seismicity suggests that the northeast dipping slab has descended to a maximum depth of 200 km in western Costa Rica. Meanwhile the Nazca Plate is pushing both plates to the northwest. Earthquakes in this country are caused by the downward movement of the Cocos Plate, plus the slippage of all three plates to the northwest. The Volcano Irazu the highest volcano in Costa Rica towers more than 10,000 feet High and covers almost 200 square miles. The word “Irazú” is actually derivative of an Indigenous word which means “thunder and earthquake mountain”. Radioactive dating has shown an age of at least 854,000 years with eruption peaks at 570,000 years and the most recent active phase from 136,000 years to present. The most recent activity includes lava flows along with strombolian and phreatomagmatic explosions. Lava types include basalt and andesite erupted during different events suggesting the volcano is fed by two distinct magma chambers. At the top of Irazú there are five craters with two major ones. The Principal Crater is 1050 meters wide and 300 meters deep while the Diego de la Haya Crater is 690 meters wide and 100 meters deep and contains a blue lake. From the summit it is possible weather permitting to see both the Caribbean and Pacific. There are few inhabitants in this harsh environment, but two you should keep an eye out for are the aptly named Volcano Junco and Volcano Hummingbird. At the top the Temperatures hover around freezing, and constant winds and saturating humidity contribute to the bitter cold at the crater. Close to the top is an array of telecommunication towers which are a main part of the country's communication infrastructure. On the Caribbean side is the Prussia Rain Forest Reserve which offers visitors the opportunity for strolls amid magnificent arboreal specimens and the source of the majestic Reventazón River. The forest is made up of conifers and exotics with a native forest consisting mainly of oaks and alder. Travelling up the volcano you will see the potato, onion, and cabbage fields give way to dairy farms at higher elevations and finally near the top is the tree line. On the road leading up to the summit is the the Sanatorio Duran which used to be a TB retreat and is reported the most haunted building in Costa Rica. After the partial collapse of the NW sector of the Irazú volcano in 1994 three caves were revealed. These caves contain some of the rarest collections of sulfurous based hydrated minerals. This includes the first occurrence in cave environments of minerals such as aplowite and bieberite. Past Eruptions Irazú’s first eruption was recorded on Feb. 16, 1723, by Costa Rican Governor Diego de la Haya Fernández, who noted that a dark column of smoke was visible over the volcano and that ashes were blown as far as Curridabat. Eruptions continued throughout the year, with major blocks of material exploding into the air and ash falling on Cartago, which was then the capital. Several eruptions followed in the 19th century and early 20th century, with wind-carried ashes at one point falling 120km to the west in the Gulf of Nicoya. In 1933 ash accumulated on the streets of San José, and there were reports of eye and nose problems. Irazú’s most famous eruption coincided with a visit to Costa Rica by President John F. Kennedy in March 1963. On March 13, the volcano began a series of Strombolian eruptions, which are considered small to medium in volume and violence, and in which incandescent cinder and lava bombs were ejected. Irazú’s eruptions, which would continue for two years, covered the Central Valley with up to 1.5m in ash. In towns near the volcano, roofs collapsed from the weight of the ash. The ash dammed a nearby small river, flooding the city of Cartago and causing serious damage to coffee crops. The prolonged ashfall severely damaged dairy, vegetable, and coffee farms, and for a while made daily life in the affected cities extremely difficult. Accelerated runoff of rainwater from the ash-covered slopes of the volcano caused destructive floods, mudflows, and landslides. Irazú’s last possible eruption (disputed) was in 1994 involved an explosion of steam, rocks. The eruption spread material over the northwest side of the volcano and later caused avalanches in the Río Sucio. Recent Activity In April 2010 the lake within Irazú's crater dwindled to only a few centimeters depth and from May to August the lake was dry enough to allow plants to grow up to 10 cm high. Water began to accumulate in September 2010 but disappeared again during the following month. Since November 2010 water returned to the crater and as late as April 2011, a shallow turquoise-blue lake was maintained. During a visit during March 2019 Volcanlogists observed some changes to the bubbling sulfur water in the Lake of the crater with some additional fumaroles on the volcano flanks. In August 2020 there was a landslide South West of the main crater with debris falling into the Sucio river. The massive landslide is reported to not have caused loss of life but did affect communications equipment which will be relocated. Specialists from the Volcanological Observatory and the National Emergency Commission analyzed the slide and reported the presence of new fissures. Discussion This is not a volcano that appears on the edge of eruption and on the face of it not the most threatening volcano if it does erupt. Lahar run off channels being illegally being built on, emergency responses possibly threatened by damaged communication channels, a history of building fires getting out of control, eruption earthquake damage and I see potential for a lot of lives being affected by an eruption especially since it can become active very quickly (highway to hell). You may see a benign volcano but are there factors that would worry you?
  24. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Pico Basile Reason for Interest There are places in the world that seem remote from the rest of world and where volcano monitoring is very rudimental. An active volcano in such a place where volcanic hazards are almost dismissed and where the volcano forms part of a dangerous line of volcanoes concerns me. The Setting Pico Basilé Volcano (formerly Pico de Santa Isabel) is on the island of Bioko (formerly Fernando Poo and Formosa). Bioko is an island some 60 miles of the western coast of Africa and is part of Equatorial Guinea. The Island is about 40 miles long and 20 miles wide with much of the south of the Island uninhabited. Malabo the capital of Equatorial Guinea is on the north coast of the Island. Equatorial Guinea is made up of the mainland (Río Muni) as well as five volcanic islands. The mainland is bordered by Gabon and Cameroon, and separated from the islands by the Gulf of Guinea. The other islands are Corisco, Great Elobey, Little Elobey and Annobón. The further south you go on the island the thicker the rainforest becomes interspersed with stately ceiba trees. Seven monkey species which are in danger of becoming extinct are on the Island along with the second largest nesting rookery for green turtles in the world. During the dry season Arena Blanca Beach (White Sand) near the western town of Luba, teems with butterflies. During the dry season the village of Ureca at the southern tip of Bioko has dark sand beaches where up to four different types of turtles come ashore. The climate would be described as tropical monsoon with the capital receiving about 70 inches of rain per year. There is a sunnier (but still cloudy) dry season from December through February. It also has a very long cloudy wet season that covers the remaining nine months (March–November). On average, the months hit hardest by the wet season September to October receive 20 inches of rain each. Daytime temperatures do not vary by a few degrees throughout the entire year with average night-time temperatures around 20–21°C in every month of the year. The capital Malabo is one of the cloudiest, wettest and most lightning-prone capitals of the world, with fog and haze even when it's not raining. The Tectonic Environment Bioko was formed along the Cameroon line, a major northeast-trending geologic fault that runs from the Atlantic Ocean into Cameroon. This line includes other volcanic islands in the Gulf of Guinea such as Annobón, Príncipe and São Tomé, along with the massive stratovolcano of Mount Cameroon. Volcanism along the Cameroon line is related to rifting – where a continent breaks into two pieces. About 110 million years ago a giant rift broke apart what became Africa and South America and the South Atlantic Ocean began to form. A smaller rift formed within the African continent. This older rift, called the Benue Trough, is north of and parallel to the Cameroon line. About 80 million years ago, during a reorganization of plate boundaries, the African plate rotated counterclockwise. Then a new rift formed that failed to split Africa but apparently did form conduits that allowed magma to ultimately reach the surface and form the volcanoes of the Cameroon line. The Volcano Pico Basilé is the highest point of Equatorial Guinea With an altitude of 3,011m.It is the largest and highest of three over lapping basaltic shield volcanoes which form Bioko island. Pico Basilé lies close to the city of Malabo with a population of 300,000 people (2018). The very top is used as a broadcast transmitting station for Radio Television Guinea Equatorial and microwave relay station for various communication networks. The peak forms a part of Pico Basilé National Park, created in April 2000.The volcano has numerous satellite cinder cones and is the only Bioko volcano with reported historical eruptions. Volcano History and Research There have been three eruptions (1998, 1903, 1923) during the late-19th and early-20th centuries reported from SE flank vents. During 2012 steam vents were observed. The eruption of 1903 formed a crater explosion and a lot of ash a new cinder cone and a small lava flow at 2400 m. GeoChemistry analyses suggests two types of volcanic products found on the Bioko Island: pyroclastic ejection (spheroid bombs, cognate blocks, lapilli, coarse and fine ash, and shiny and black scoriae) and lava flows. The majority of eruptions produced on the Bioko Island are typically strombolian. Vents are often more or less opened fractures, and many of them can be simultaneously active. Explosive vents are mild, with average projected height up to 300–400 m high. In November 2017 Drexel University researchers including Amanda Lough who specializes in Deep long period earthquakes installed 4 broadband seismometers on Bioko. Preliminary results show there is seismicity associated with Bioko Island as well as Cameroon. Surprisingly many of the seismic events from Bioko Island were from the southern end of the island and offshore. Discussion Putting together even this basic introduction was difficult any I am surprised that it is difficult to answer even basic questions about eruptive history. Considering this volcano overlooks a capital city and that capital city sits on the rim of an extinct volcanic crater, you would think there would be more documentation. I suspect the hazards to people is limited from the Volcano but there is so little study it is hard to know for sure. The question for me is why there is no global interest and ambition or funding to find out. Since this is Netweather perhaps the real question is how do people cope with such a wet climate?
  25. Introduction My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles. Introducing Volcano San Salvador (El Boquerón and the Quezaltepeque volcanic center) Reason for Interest The volcano El Boquerón (Big Mouth) towers above the capital city San Salvador of El Salvador. Historical landslides, earthquakes and eruptions have affected populated areas. This is a volcano which can cause problems without eruption yet in many ways seems so benign. The Setting El Salvador is a small central American Pacific Coast country with Honduras to the North and East and Guatemala to the West with an Ocean to the south. The Sierra Madre Mountain range is in the North along the border with Honduras. Further south is the coastal Mountain range which is split into five groups of active volcano groups. The lowlands along the coast have a tropical climate with mango, coconut and Cashew trees, the plateau between the mountain ranges has a semitropical climate and mountain areas experience more temperate weather with pine and oak. Temperatures typically ranging from 60 to 85 Degrees Centigrade with a wet winter season from May to September. The wet season rain comes from low pressure systems forming in the Pacific often leading to Thunderstorms (often in the afternoon or overnight). The country has frequent earthquakes with a history of significant damage to buildings in the past (1951, 1965, 1982, 1986 and 2001). Volcanic activity occurs periodically with the large VEI6 eruption of llopango in the 5th century most notable. The economy is notable for indigo, coffee, fruit and more recently for surfing. Due to the use of the U.S. Dollar as a currency El Salvador is becoming more Americanized with shopping malls and boutique Hotels beginning to crop up. Parts of El Salvador are troubled by gangs and corruption so it can be risky to visit despite its growing Americanization. El Salvador is known for its gorgeous flowering trees, the Maquilishuat the pink-tufted national tree, the beautiful Roble Colorado with its fuchsia and the Arbol de Fuego a tree with brilliant orange flowers. This is also home for armadillos, anteaters, sloths, ocelots, jaguar, spider monkeys, parrots, parakeets, boa constrictors, turtles, coatis and the national animal the Turquoise-Browed Motmot. The Tectonic Environment Most of Central America rests on the relatively motionless Caribbean Plate. The Cocos Plate close offshore in the Pacific is being carried northeast and sub-ducting below the Caribbean Plate. The Pacific relatively dense ocean floor is forced down under the lighter land mass, creating the deep Middle America Trench that lies off the coast of El Salvador. The subduction of the Cocos Plate accounts for the frequency of earthquakes near the coast. As the rocks of the ocean floor are forced down, they melt, and the molten material pours up through weaknesses in the surface rock feeding volcanoes. The Volcano The summit area of the volcano just below 6000 feet high is within a national park (Parque El Boquerón). The park is covered with a pine forest with exotic flowers such as cartuchos, hydrangeas, hibiscus, calla lilies and begonias to be seen along the trails through the park giving a sensual overload of fragrances. The park also has a visitor center and trails leading up to the 5km wide crater with four viewing points along about a 50m section of the rim. Within the 558m deep crater is Boqueroncito (Little mouth) a cinder cone from the last eruption which can be visited by those intrepid enough to venture down the steep walls of the crater. Timeline of the last eruption On June 7th 1917 after the celebrations of the Eucharist, the population surrounding the volcano of San Salvador felt the devastating effect of a large earthquake at approximately 6:55 pm. This earthquake and the subsequent tremors caused severe damage to nearby towns and villages. At 8:11 pm the Pinar hill on the northern side of the volcano, developed small craters (Boqueroncitos), from which clouds of black smoke rose to the sky. This was followed by a 250m wide and 2km long river of magma that flowed passed the community of Las Granadas. At around 8:45 pm another slightly lesser earthquake was felt. This earthquake coincided with the start of a new eruption from the craters of “los chintos” specifically from the lower crater “el tronador”. Magma flowed to the north covering a length of 6.5 km and had a width of 100m. This large blanket of magma sliced the railway line from Quetzaltepec to El Sitio del Niño. On the 9th of June the main crater began to erupt. During the afternoon the water that had once formed the lake in the crater slowly began to evaporated, forming a thick cloud of smoke. By the 28th the water had completely disappeared and there were explosions that sent up columns of hot mud and ash. The ashes expelled from the eruption fell over many nearby towns and villages. In November 1917 the eruption that began on the 7 of June came to an end. The most devastating event being the initial earthquake which destroyed most of the buildings nearby with later ash fall further destroying buildings. It was reported that although the death toll was relatively low that a large percentage of houses in San Salvador were uninhabitable, water supplies were severely damaged, and the entire business section destroyed by fire. Most Recent Activity On the 22nd of Mar 2012 t the Mexican 7.4 magnitude earthquake near Acapulco might have affected the currently dormant San Salvador volcano by triggering an earthquake swarm under the volcano. The swarm consisted of 25 quakes, including 8 quakes between magnitude 2.2 and 3.3. The quakes were located at shallow depths between 0.5 and 5.8 km under the volcano. During October 2020 at least nine people were killed after torrential rain caused a landslide on the northeast flank of the volcano. The landslide tore a 4 km path through the village of Los Angelitos, and Nejapa where 60 homes were buried and 75 damaged. Volcano History Eruptions have typically been flank eruptions along two or three fault zones with most recent ones being along a N40W fault zone through the central volcano. Some of these flank eruption craters are “La Joya”, “Boqueroncillo”, “Los Chintos” and “El Playón”. The last eruption south of the main caldera was 1700 years ago with most recent activity to the North West furthest from the city of San Salvador. One historic eruption of San Salvador involved a caldera collapse and left deposits up to 4m deep up to 4km away and lighter deposits up to 18km. A further major eruption and caldera collapse in 1200 AD covered an area of 300km2 with ash. In 1976, a bulldozer operator leveling ground uncovered a building covered in volcanic ash. The building was part of a peasant community of Mayans later found to be to be 1400 years old. Dan Miller, a USGS geologist determined the ash came for a hydro magmatic explosion crater approximately 400 m. away. The village was covered by more than 4m of volcanic material. Sediments suggest that the eruption was explosive and hurled material at a high velocity. Discussion Ideas For me the most disturbing and perhaps overlooked hazard is the simple risk of water supply damage and fire risk to a city from a volcanic earthquake. There also seems to be a lot of communications equipment on the volcano which is a bit worrying. Perhaps you have a different view and the risks are minimal or different? Maybe you want to explore some of the things I skipped over a bit, like deforestation, El Salvador gangs, civil wars, history, llopango, wildlife, trees and flowers.
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