The sound of ocean waves lapping on the beach could prove handy for more than just helping people sleep: they may help predict when a volcano is about to wake up.
When some land volcanoes are preparing to erupt, telltale changes on the surface can reveal a build-up of magma, but if the magma chamber is at depth there may be little sign of a pending eruption, says Florent Brenguier at the University of Grenoble in France.
Now Brenguier鈥檚 team has found a way to monitor such inscrutable volcanoes. When ocean waves break, they send low-frequency shock waves over great distances through the Earth鈥檚 crust. The team found that these shock waves slow down if they pass through the magma chamber of a volcano that is experiencing pre-eruption rumbles. Placing about 20 sensors around a volcano could give a detailed picture of any changes at depth, says Brenguier.
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The team correctly forecasted eruptions of the Piton de la Fournaise volcano on the island of R茅union in the Indian Ocean in July 2006 and April 2007 as much as 10 days in advance (Nature Geoscience, ).
Other natural seismic sources could also be used, says Brenguier, such as wind battering the ground. Even traffic might work, although its high-frequency waves cannot penetrate as deeply as ocean-generated ones, he says.
