November 27, 2020

I, Science

The science magazine of Imperial College

Predicting volcanic eruptions is notoriously tough. Tracking movements of molten rock hundreds of metres below the Earth’s surface is never going to be easy, but scientists now claim they’ll know exactly when Sicily’s Mount Etna is next about to blow.

Etna is one of the world’s most active volcanoes. Its erratic eruptions have claimed 72 lives in the last couple of centuries and, with thousands of tourists scaling its blackened flanks every year, volcanologists have been working to avert a catastrophe.

Using data from the 2001-2003 eruptions, a team from Italy and Spain have discovered that changing seismic wave intensity of Etna’s earthquakes is a clear indicator of an imminent explosion.

When magma – molten rock – forces its way towards the surface, it sets off a series of small tremors as cracks and fissures open up. Seismic waves from these earthquakes can be picked up by sensors placed around volcanoes and scientists monitor activity to predict the magma’s movements.

Seismic waves are affected by the temperature of the rock they’re traveling through – as temperature rises, wave intensity falls. Using data from several sensors at Etna, the team tracked the intensity of seismic waves generated between 2001 and 2003.

Their results, published in this month’s Geology journal, show a sharp intensity drop just before the major eruptions. In 2003, the fall corresponded to a predicted 70-80⁰C temperature rise as magma broke through into the rocks just below the surface.

During the 2001 eruptions, the seismic wave weakening came days before a big explosion. But in 2003, it gave only a few hours notice. The volcanologist are now looking at rapid ways of processing the large amounts of data picked up by Etna’s seismographs, so they can identify the intensity drops and get people off the mountain before it devours them.