Wednesday, 27 June 2018

Evacuations ordered after eruption on Sierra Negra volcano, the Galápagos.

Around 250 people have been evacuated from homes around Sierra Negra, a 1124 m shield volcano (dome shaped volcano made up of layers of lava) on the eastern end ot Isabela Island, the Galápagos, on Tuesday 26 June 2018. The Instituto Geofísico-Escuela Politécnica Nacional recorded a sudden rise in seismic activity (Earthquakes) beneath the volcano from about 11.15 am local time, with Earthquakes between three and five kilometres beneath the surface, and with a maximum Magnitude of about 4.7. At about the same time, the GOES-16 Satelite, which is operated by the US National Oceanic and Atmospheric Administration and which is in a geostationary orbit, enabling it to monitor the region permanently, detected a thermal anomaly in the area of the volcano, probably indicating lava on the surface., with the eruption being directly observed by witnesses later that afternoon.

Eruption on Sierra Negra volcano, Isabela Island, on 26 June 2018. Xavier Garcia/Tarsicio Granizo/Twitter.

Sierra Negra  is the largest volcano in the Galápagos in terms of area, covering an area of about 7.2 by 9.3 km, and one of the most active, having last erupted in October 2005. It is estimated to be about 535 000 years old from its volume and rate of eruption, though it is hard to precisely date, as Isobela Island is made up of a series of overlapping volcanoes, making it difficult to assess the origin of the oldest lava deposits.

The volcanos of the Galapagos are fuelled by a mantle plume, the Galapagos Hotspot, an upwelling of hot magma from deep within the Earth’s mantle which pierces the overlying Nazca Plate, and moves independently of it. This plume transverses the plate at a rate of 0.46 degrees per million years, which has led to the formation of the string of volcanoes which form the Galapagos Islands. However analysis of the geochemical composition of the lavas of Wolf Volcano has shown that these are distinct from the lavas of the neighbouring Ecuador and Darwin volcanoes, but show strong similarities to lavas produced on the Galapagos Spreading Center over 200 km to the north, a trait shared with lavas from other Galapagos volcanoes, most notably Santa Cruz and Genovesa, suggesting that there is some interplay between these two sources.

The relative positions of the Galapagos Islands and Galapagos Spreading Center. School of Ocean and Earth Science and Technology/University of Hawaii at Manoa.

See also...

http://sciencythoughts.blogspot.com/2018/02/british-tourist-attacked-by-shark-while.htmlhttp://sciencythoughts.blogspot.com/2015/05/eruption-on-wolf-volcano.html
http://sciencythoughts.blogspot.com/2012/06/death-of-lonesome-george-and-extinction.html
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