Between a Rock and a Hard Place

Science snap

Science Snaps (4): vivid volcanoes

This week we couldn’t just stick to one “Science Snap” so we went for four – one from each of the contributors! We’ve all chosen a volcano dear to our hearts being ones we’ve either visited or studied.

James: This photo was taken during fieldwork in 2012. The giant Uturuncu volcano in southern Bolivia has been slowly uplifting for over 45 years. High-precision GPS and micro-gravimetry in the foreground are being used to monitor the volcano and better understand the subsurface dynamics driving its expansion

James: The giant Uturuncu volcano in southern Bolivia has been slowly uplifting for over 45 years. High-precision GPS and micro-gravimetry in the foreground are being used to monitor the volcano and better understand the subsurface dynamics driving its expansion. This photo was taken during fieldwork in 2012. Credit: James Hickey

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Science Snap (3): Earth’s biggest volcano?

Screen Shot 2013-09-10 at 10.09.48James Hickey is a PhD student in the School of Earth Sciences at the University of Bristol. A geophysicist and volcanologist by trade, his PhD project is focussed on attempting to place constraints on volcanic unrest using integrated geodetic modelling.

 

 

 

The newly discovered submarine Tamu Massif (pictured below), approximately 1500 km east of Japan, has been proposed as the world’s largest volcano. At ~450 km x 650 km it dwarfs Mauna Loa of Hawaii by a factor of 50 in its spatial extent, and is comparable in size to Olympus Mons on Mars (as well as the United Kingdom!).

The seismically-imaged Tamu Massif. Image credit: BBC News.

The seismically-imaged Tamu Massif. Image credit: BBC News.

What marks this volcano out as being so special is that rather than consisting of a group of individual volcanoes, it is believed to be one single system. Seismic studies have shown the layers of lava that build up the giant volcano all originate from one single vent. They then slope outwards from the centre to form a very broad shield-like massif.

Samples taken on the volcano by the Integrated Ocean Drilling Program show very little chemical variability and indicate an age of ~145 million years. At this time, Tamu Massif is believed to have formed at a triple junction between three tectonic plates. But quite how so much lava managed to make its way through the crust in potentially one prolonged event remains unclear. Equally intriguing is the prospect of more of these structures existing – now we have unearthed one from its hiding place, maybe many more will follow…

Science snaps (2): Soufrière Saint Vincent

Soufrière Saint Vincent is youngest volcanic centre on the Caribbean island of St Vincent. A stratovolcano some 1,230m in height, La Soufrière has erupted five times in the last three hundred years, most notably in 1902 when 1,680 people were killed. The explosive volcanism here is the surface manifestation of the slow, westwards subduction of the American plate beneath the Caribbean plate, and is part of the 750 km-long volcanic chain of the Lesser Antilles.

The image below shows two views of the summit crater either side of a VEI 3 eruption in 1979. The most striking difference between the two photos is the disappearance of the crater lake; prior to the 1979 eruption it was possible to row out to the lava dome to take samples! Although the blocky andesitic lava dome (~ 130m high and 840m wide) appears in both images, it was in fact destroyed in the 1979 eruption, with the current pile of lava representing new growth. Fumerolic activity was higher in 1972, though the present-day dome does show evidence of gas-venting on one side (aptly, La Soufrière is French for The Sulphurer). Monitoring of the volcanic system on St Vincent is carried out by the Seismic Research Unit of the University of the West Indies.

sourfriere

Soufrière Saint Vincent, Lesser Antilles. Two images taken either side of a VEI 3 eruption in 1979.