The eruption of some of the largest volcanoes on the
planet could be predicted several decades before the event, according to
researchers.
Analysis of rock crystals from the Greek island of Santorini suggests
eruptions are preceded by a fast build-up of magma underground, which might be
detected using modern instrumentation.
Such volcanoes can produce enough ash and gas to temporarily change the
global climate.
The research
is in the journal Nature.
Volcanologists refer to history's largest volcanoes as "caldera-forming
eruptions", as the magma ejected is so voluminous that it leaves a massive
depression on the Earth's surface and a crater-like structure known as a
caldera.
The largest of these volcanoes have been dubbed "supervolcanoes"
and their eruptions can trigger devastation with global impacts.
Such volcanoes can lie dormant for hundreds of thousands of years before
blowing. But while researchers believe seismic data and other readings would
give us a few month's notice of such an eruption, the new study suggests we
might anticipate these events much earlier.
"When volcanoes awaken and when the magma starts to ascend to the
surface, cracking rock as it does, it sends out signals," Prof Tim Druitt
of France's Blaise Pascal University and lead researcher told BBC News.
"You get seismic signals, you get deformation of the surface,
increasing gas emission at the surface - and this can be detected.
"The question we're addressing here is what's going on at depth prior
to these big eruptions. The classical view was that during long repose periods
over thousands of years, magma slowly accumulates a few kilometres below the
volcano and finally it blows.
"What we're finding is that
there's an acceleration phase of magma build-up on a time scale of a few
decades, and that's surprisingly short given the thousands of years of repose
that have preceded that eruption."
The evidence comes from analysis of
crystals in pumice rock from the Santorini site, which the researchers in
France, Switzerland and Singapore analysed using modern instrumentation
including electron and ion microprobes.
"The changes in composition of
the crystals with time provide |