Volcanoes don't sleep as long as you think, study shows
If you've ever thought of camping in the vicinity of a volcano, you may want to rethink your plan. Contrary to popular belief, volcanoes do not remain inactive for centuries. Researchers from France and the US, partly funded by the EU, have shown that volcanoes can burst within a matter of weeks, rather than years. Their discovery could encourage scientists to reassess the threat from dormant volcanoes, potentially leading to new emergency planning and evacuation procedures. The study, presented in the journal Nature, was funded in part by the DEMONS ('Deciphering eruptions by modelling outputs of natural systems') project, which has clinched a European Research Council (ERC) Starting Grant worth EUR 1.36 million under the Seventh Framework Programme (FP7). Dr Alain Burgisser of France's Institut des Sciences de la Terre d'Orléans, (CNRS/INSU (Centre national de la recherche scientifique/Institut national des sciences de l'univers), Université d'Orléans, Université François Rabelais-Tours), along with Professor George W. Bergantz from the Department of Earth and Space Sciences at the University of Washington in the US, developed and tested a theoretical model on two major eruptions, providing fresh insight into an age-old theory about slumbering volcanoes. According to the researchers, the reawakening of a magma chamber could occur within just a few months. Magma chambers are large underground pools of molten rock found many kilometres (km) beneath the surface of the Earth. The molten rock tolerates high pressure levels, and as time passes, this pressure can fracture the rock around it, opening channels for the magma to escape. The magma surfaces, triggering a volcanic eruption. While magma chambers are for the most part difficult to detect, scientists have located them close the surface of the Earth, anywhere between 1 km and 10 km underground. The big question is: what happens to the magma chamber when a volcano is dormant? Scientists say the chamber cools down to thick mush until fresh magma 'reawakens' it. The magma chamber is then 'fluidised' when heated via thermal contact. So the size of the magma chambers - from a few tenths to a few hundred cubic kilometres - has a direct impact on how quickly a volcano comes back to life. Conventional volcanologists say it could take anywhere between several hundred or 1,000 years for the entire reservoir to feel the heat, and then kick-start the volcano's flow of lava. Here is where the findings unearthed by this Franco-US team become interesting. The new mathematical model suggests the reheating occurs in three stages. The fresh hot magma melts the viscous magma at the base of the reservoir after rising from below and reaching the chamber. The molten magma becomes less dense and surfaces via the chamber, thus helping mix the remaining viscous mush. This mix allows the heat to move through the chamber at significantly faster speeds than what scientists thought possible. So the size of the chamber and the magma's viscosity plays a critical role in fuelling a volcano's reawakening much earlier than previously thought. The researchers tested their model's validity against the 1991 Mount Pinatubo (Philippines) eruption and the ongoing eruption of the Soufriere Hills volcano in Montserrat in the Caribbean. Their findings show that the seismic shocks preceding the eruption are an indication of the emergence of fresh magma beneath the cooling reservoir. They reproduced the time intervals between the warming signals and eruptions after considering the physical parameters of both volcanoes, namely chamber size, magma temperatures and crystal concentration inferred from the study of magmas. The Pinatubo case, for instance, suggests that contrary to the 500 years previously thought, 20 to 80 days were enough to remobilise the underlying chamber. The sophisticated model developed by the team could help scientists estimate the time lapse between a volcano's first tremors and its eruption in the future. For more information, please visit: Nature: http://www.nature.com/ Institut des Sciences de la Terre d'Orléans: http://www.isto.cnrs-orleans.fr/ University of Washington: http://www.washington.edu/European Research Council (ERC): http://erc.europa.eu/ FP7-IDEAS:http://ec.europa.eu/research/fp7/index_en.cfm?pg=ideas DEMONS project factsheet on CORDIS, click: here //RMK
Countries
France, United States