An eruption over 520,000 years ago shows South Aegean Volcanic Arc was far more dangerous

Newly discovered evidence of one of the most massive eruptions ever recorded in the South Aegean Volcanic Arc suggests that the field was much more explosive in the distant past than previously believed.

According to the research published in the journalCommunications Earth & Environment,scientists have extracted an enormous pumice deposit from the seafloor of coastal sites of the Greek archipelago in Santorini.

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The 60-kilometre chain of over 20 volcanoes makes up the volcanic field in the Greek Aegean. Most of these dangerous volcanoes are underwater and have a history of highly explosive eruptions.

Dr Steffen Kutterolf, a volcanist at the GEOMAR Helmholtz Centre for Ocean Research in Kiel and Dr Timothy Druitt from the University of Clermont-Auvergne led the expedition in Santorini.

Dr Kutterolf said, "For example, the Late Bronze Age eruption of Santorini around 3,600 years ago probably triggered the downfall of the Minoan civilization on Crete—an important event for both volcanology and archaeology."

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The deposit suggested that a more explosive eruption took place over 520,000 years ago. "The newly discovered tuff deposit has a volume of more than 90 cubic kilometres and is up to 150 meters thick, making it six times larger than the pyroclastic flow deposits of the Minoan eruption and ten times larger than those of the Hunga Tonga-Hunga Ha'apai volcanic eruption of 22 January 2022," Dr Kutterolf added.

The streams of hot ash, rock, and gas originating from a submarine volcano are known as pyroclastic flows. When combined with water, they transform into turbid flows and mud.

Pyroclastic flows transported large quantities of volcanic material up to 70 kilometres into the nearby sea basins. Researchers have also found layers of rock belonging to the same eruption as the deposit on three neighbouring islands.

Dr. Kutterolf said, "The first dating and estimation of the water depth at which the eruption took place were possible directly on board thanks to micropalaeontology." Since the geological age and preferred water depths are known, the research team used microfossils (foraminifera) found above and below the pumice deposit to determine its location on the seafloor.

However, researchers believe that the chances of the volcanic field experiencing another eruption of high magnitude are low. "But knowing the past is also an essential building block for predicting the future," says Dr Kutterolf.

(With inputs from agencies)