PARIS: Around 1630 BC, a super-volcano blew apart the Aegean island of Santorini, an event so violent that some theorists say it nurtured the legend of Atlantis.

More than three and a half millennia later, the big blast is yielding forensic clues which help the search to predict future cataclysmic eruptions, scientists said on Wednesday.

Bigger than the destruction of Indonesia’s Krakatoa in 1883, the Santorini event was a so-called caldera eruption, a kind that happens mercifully only at intervals of tens of thousands of years, sometimes far more.

The chamber of a volcano becomes progressively filled with magma but lacks vents from which to discharge this dangerous buildup of gas and molten rock.

The pressure cooker culminates in catastrophe, ripping off the top of the volcano and leaving a depression called a caldera, the Spanish word for cauldron.

One of the great unknowns is when a caldera-type episode is in the offing.

That question is a particular concern for Yellowstone Park in Wyoming, a truly massive volcano classified as “high-threat” by the US Geological Survey (USGS).

Vulcanologists led by French-based Timothy Druitt scrutinised crystals of a mineral called feldspar that had been ejected from the Santorini eruption.

They looked for traces of magnesium, strontium and titanium, deposited in waves over thousands of years by the slowly advancing magma. The chemicals, they found, were a telltale of events over time.

From these signatures, the picture that emerges is of final, fatal spurts of magma injection which happened in the last decades — maybe even just the final months -— before the great eruption.

The study, reported in the journal Nature, chimes with other research that suggests magma reservoirs in caldera volcanoes undergo a “pulsatory” buildup which probably accelerate before eruption.—AFP