EARTH SCIENCES
Nailing down the timing of a volcanic eruption is tricky, but gases hissing from vents might be the warning we need.
– Burps from the Earth predict volcanic blasts
The folks living near Campi Flegrei have a right to be nervous. This picture-perfect region of Naples is situated next to a super volcano that has lain dormant for 500 years. Scientists suspect that may be about to change. But when?
A new technique may calm the Neapolitan nerves. A study published in Nature Geoscience in February shows the composition of gases in the magma chamber beneath a volcano changes dramatically in the lead-up to an explosion. Monitoring these changes may give surrounding towns precious time to evacuate.
Predicting when a volcano will erupt is notoriously difficult – especially when it’s lain dormant for centuries. Scientists have tried to translate ground movements, caused by rising pressure from magma in underground chambers, into warnings. But it doesn’t always work. Some volcanoes can build pressure for millennia without exploding.
So researchers led by Mike Stock from the Department of Earth Sciences at the University of Oxford sought a better warning sign. They analysed tiny crystals of apatite found near the volcano. Spewed from Campi Flegrei during an active period 4,000 years ago, some were released in occasional splutters; others from a full-blown eruption. Based on their age (ascertained by radioactive dating), they could compare their composition to the volcano’s activity. In particular the crystals locked gas molecules inside, offering a snapshot of the gas composition of the magma as the volcano rumbled.
During splutters, the magma was relatively bubble-free. Just before an eruption, it became very gassy. The findings suggest, worryingly, that rather than a slow build, eruptions can occur quite suddenly when a big batch of gassy magma percolates from deeper in the mantle.
The good news is some of these gases would vent to the surface. “Our findings suggest that, rather than seismic activity and ground deformation, a better sign of an impending eruption might be a change in the composition of gases emitted at the Earth’s surface … potentially providing an early warning sign,” says Stock.