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Not a lake in a volcano, but a ‘lake’ under a volcano

Researchers from the University of Bristol discovered recently that under dormant Uturuncu volcano in the Bolivian Andes lays a massive reservoir of water. However, do not imagine this ‘lake’ as a cavern full of flowing water, but more as a space where water is dissolved in partially molten rock at 950 to 1000 °C. The partially molten lava contains approximately 9-10 % of water. The space is located 15 km beneath the volcano and houses half a million cubic kilometers of water. This is comparable to some of the largest freshwater lakes on the planet.

Beginning in the 1980s (with a peak between 1992-98) Uturuncu actually became known the largest growing volcano on the planet. On average it inflates with a centimeter a year as magma is pumped from the magma chamber into the volcano. Nevertheless, the last time the volcano erupted was about 271,000 years ago. Volcanologists do however believe that if she decided to wake up again, it could be massive. It seems likely that the water reservoir is a major driving force behind eruptions.

Recent discoveries of large volumes of water under volcanoes and in the earth’s interior add to growing evidence that the earths water might have originated from within rather than from outside (icy comets and such). Thus, these large water reservoirs could be the source of today’s oceans. Also, it seems likely that water could be the driving force behind certain (explosive) volcanic eruptions. Examples of other volcanoes that could contain water reservoirs below them are Mt St Helens in the United States and the Taupo Volcanic Zone in New Zealand.

Uturuncu certainly does not host the largest body of water under the surface. In 2014 scientists discovered a reservoir of water deep beneath the earth’s surface that could be three time the volume of the oceans together. The water is hidden in the mantle, 700km below us inside a pocket of blue rock called ringwoodite. The team from Northwestern University, Illinois made this remarkable discovery by detecting seismic waves. These waves can be measured at the surface as they move through the entire interior (even the core) of the earth. The team figured out what types of rocks the waves were moving through by measuring the velocity of waved in different depths. It takes longer for waves to move through wet rock than dry rock and thus, the water reservoir was revealed when the waves slowed down.

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Image 1: 6008m high Uturuncu volcano is the highest peak of Bolivia. http://bit.ly/2eAkafb. Image 2: Courtesy of Oregon State University. References: http://bit.ly/2ewo8pg http://bit.ly/1QFhPNU http://volcano.si.edu/volcano.cfm?vn=355838