A huge gigantic lake have been unearthed under a dormant volcano by Scientists in South America. The lake was discovered 15 km below the volcano, a finding that could unlock why and how volcanoes erupt.
That’s only partially true. There is no actual lake under Cerro Uturuncu — but there is an incredible amount of water locked up in the melted rock beneath the volcano, approximately enough to fill Lake Superior. This sort of dissolved water is a well known driver of eruptions for volcanoes in subduction zones, where one piece of the earth’s crust is being pushed under another. Still, scientists were surprised at the sheer amount of water trapped beneath Cerro Uturuncu.
Involved in the new research that discovered the massive store of water, Jon Blundy, a petrologist of University of Bristol, said, “It’s probably about twice as much as would have been expected.”
University of Bristol in the UK and colleagues have found the lake, that has led scientists to consider if similar bodies of water may be hiding under other volcanoes and could explain the secret behind volcano eruption.
Blundy said, “The Bolivian Altiplano has been the site of extensive volcanism over past 10 million years, although there are no currently active volcanoes there.”
He added that The Altiplano is underlain by a large geophysical anomaly at depths of 15 km below the surface of Earth. This anomaly has a volume of one-and-a-half million cubic kilometers or more and is characterized by reduced seismic wave speeds and increased electrical conductivity. This indicates the presence of molten rock. The rock is not fully molten, but partially molten. Only about 10%-20% of the rock is liquid and the rest is solid. The rock at these depths is at a temperature of about 970oc.
In order to characterize the partially molten region, the team performed high temperature and pressure experiments at the University of Orleans in France.
This measured the electrical conductivity of the molten rock in the ‘anomalous’ region and concluded that there must be about 8%-10% of water dissolved in the silicate melt.
“This is a large value. It agrees with estimates made for the volcanic rocks of Uturuncu using high temperature and pressure experiments to match the chemical composition of crystals,” said Blundy.
“Silicate melt can only dissolve water at high pressure; at lower pressure this water comes out of the solution and forms bubbles. Crucially – these bubbles can drive volcanic eruptions. The eight to ten per cent of water dissolved in the massive anomaly region amounts to a total mass of water equivalent to what is found in some of the giant freshwater lakes of North America,” Blundy said.
Professor Fabrice Gaillard, University of Orleans in the US said, “Ten per cent by weight of dissolved water means that there is one molecule of water for every three molecules of silicate.”
He added that this is an extraordinarily large fraction of water, helping to explain why these silicate liquids are so electrically conductive.
The researchers hope that better understanding of how water can trigger volcanic eruptions can improve predictions of when it is going to erupt.