A Volcanic Explosion 520,000 Years Ago Dwarfed One That Devastated the Minoan Civilization

An undersea eruption a half million years ago was much larger than nearly anything recorded in human time.

Kevin Krajick
January 16, 2024
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Drilling aboard the research vessel JOIDES Resolution revealed a thick layer of ancient volcanic debris around the Greek island of Santorini, seen in the far background. (Thomas Ronge)

The ancient Minoans, generally considered Europe’s first major civilization, flourished on and around the Mediterranean island of Crete starting about 3000 BC. Around 1600 BC, one of the biggest volcanic explosions in human history blasted away much of the nearby island of Thera, obliterating communities and farmlands with hot ash, tsunamis and earthquakes. Some archaeologists think the disaster may have started the decline and fall of the Minoans, whose culture fell apart in following centuries. Others say it could have inspired the legend of Atlantis, the lost world said to have sunk into the sea.

Now, scientists drilling deep into the seabed near the remains of Thera have found evidence of a far greater explosion in this area. Some 520,000 years ago, an underwater eruption hurled a fiery slurry through the sea, and broke through to the air above. As the debris settled, it formed a submarine layer of pumice up to 150 meters thick as far as 70 kilometers from the eruption site. The researchers estimate the event was 30 times bigger than the Minoan eruption. It didn’t disturb humans; there were none around that long ago. But the discovery “highlights the hazards from submarine explosive eruptions” in the center of Europe, the team writes in a new paper just published in the journal Communications Earth & Environment.

The remains of Thera are now known as the spectacularly beautiful Greek island of Santorini. Visited by 2 million tourists each year, it is just a fragment of its former self—a rugged semicircle partly surrounding the sea-filled crater that used to be Thera’s center. Previous research has showed that the 1600 BC Minoan eruption was the last of a dozen such blowups in the area during the last 360,000 years. Since then, things have generally remained calm. A much lesser eruption at a submarine volcano near Santorini killed 70 people in 1650; the last activity at Santorini itself was some minor rumbling and lava flows on small sub-islands within the crater, in 1950.

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At sea on the drill ship, Ally Peccia, a graduate student at Lamont-Doherty Earth Observatory, characterizes cores containing volcanic sediment. (Jonas Preine/University of Hamburg)

Most studies of past volcanism in the area have been confined to land, where erosion of deposits left by eruptions often limits the timeframe that researchers can study. Scientists suspected there was much more to be learned from the seabed, where seismic profiles outlined large deposits of apparent ancient debris. Added motivation to drill came with subterranean rumbling around Santorini in 2010-11, then studies in 2020 and 2022 showing that magma was collecting near the island.

The new research was carried out as part of the International Ocean Discovery Program aboard the specialized drilling ship JOIDES Resolution. Over a two-month period in the winter of 2022-23, the crew drilled cores penetrating as far as 900 meters under the seabed at 12 sites. At most of the sites, they turned up thick deposits of whitish pumice; subsequent work showed that it all dated to the same time. The researchers have named the deposit the Archaeos Tuff.

The scientists are unsure exactly where the great eruption took place, since the landscape and seascape have been repeatedly reshaped by subsequent eruptions and overlapping craters. But they know it had to be along a 100-meter arc of volcanism called the Kolumbo Volcanic Chain, of which Santorini is a part. They also know it was really big; the gigantic Hunga Tonga-Hunga Ha’apai submarine explosion in the south Pacific that shook the world in 2022, one of the world’s biggest documented such events, appears to have been one-tenth the size of the Santorini event.

The expedition included 32 scientists from nine countries. Ally Peccia, a graduate student at Columbia University’s Lamont-Doherty Earth Observatory, was part of a team that analyzed the cores as they were hauled aboard. “We kept seeing the same material, and we could correlate it,” she said. “It was exciting, because we were the first humans to see these massive submarine deposits.”

The scientists say that while the research opens a window to the past, it is highly unlikely that an eruption anywhere near the scale of the ancient ones will take place in modern times. As if to emphasize the point, they will gather in April on Santorini itself for a post-expedition meeting.