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  • Location: Coventry,Warwickshire
  • Location: Coventry,Warwickshire

    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

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    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.

    Bioko.thumb.png.b81733c948788a8d547c631ac7afab22.png

    Malabo the capital of Equatorial Guinea is on the north coast of the Island.

    Equatorial-Guinea-Malabo.thumb.jpg.904f54d5dde33c507f1c01ed8849849f.jpg

     

     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

    847554483_Cameroonline.thumb.png.89031ccc062a32b9507d87f63a8af9ac.png

    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?
     

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