Introducing Volcanic Island Pantelleria

[BrickFielder]

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.