Watching the waves may not only be a relaxing pastime, but could also provide warnings of volcanic eruptions, according to a new paper in the journal Nature Geoscience.

Lead author of the paper, seismologist Florent Brenguier from the University of Grenoble, France, has spent several years working on the island of Réunion in the Indian Ocean, monitoring changes to the Piton de la Fournaise – ‘peak of the furnace’ – one of the world’s most active volcanoes, using the vibrations created by waves breaking on the shore.

According to Brenguier and his team, when a band of seawater strikes the coast, it sends low-frequency waves through the Earth’s crust that can be closely monitored to give a profile of the magma. Small changes to the speed of the seismic waves can indicate a build-up of pressure within the magma reservoir, indicating that an eruption is imminent.

The team placed sensors around the 2,632-metre volcano and found that this gave a detailed profile of pre-eruption activity at depth. Using these data, the team correctly forecasted eruptions in July 2006 and April 2007 as much as ten days in advance, but Brenguier points out that there is still much to be done before this technique can be used to avert disaster.

‘We are now starting to apply the technique on more explosive volcanoes such as the Ubinas (Peru), but we believe that this technique will, in a few years, be widespread and contribute to a better forecasting of volcanic eruptions,’ said Brenguier.