No Dormant Volcanos?

Until now it was thought that once a volcano's magma chamber had cooled down it remained dormant for centuries before it could be remobilized by fresh magma. A theoretical model developed by Alain Burgisser of the Orléans Institute of Earth Sciences (Institut des Sciences de la Terre d'Orléans -- CNRS/Universités d'Orléans et de Tours) together with a US researcher, was tested on two major eruptions and completely overturned this hypothesis: the reawakening of a chamber could take place in just a few months. This research should lead to a reassessment of the dangerousness of some dormant volcanoes.

It is published in the journal Nature dated 3 March 2011.

A magma chamber is a large reservoir of molten rock (magma) located several kilometers beneath a volcano, which it feeds with magma. But what happens to the magma chamber when the volcano is not erupting? According to volcanologists, it cools down to an extremely viscous mush until fresh magma from deep inside Earth 'reawakens' it, in other words fluidizes it by heating it through thermal contact. The large size of magma chambers (ranging from a few tenths to a few hundred cubic kilometers) explains why, according to this theory, it takes several hundred or even thousand years for the heat to spread to the whole reservoir, awakening the volcano from its dormant state.…