Around 3,500 years ago, a series of colossal explosions tore apart Thera, the largest of the five Santorini islands, today one of Greece’s most popular vacation spots. Current estimates suggest Thera’s eruption was the biggest volcanic cataclysm since the last Ice Age—ten times more powerful than Indonesia’s Krakatau in 1883, which triggered 140 feet-high tsunamis that killed at least 36,000 people. It must have been a terrifying experience for the Minoans. Thera’s blasts hurled a plume of ash and rock 20 miles high into the stratosphere, turning day into night.

Yet for decades, hard evidence for Thera’s impact on the Minoans has proven surprisingly elusive. And now, new findings cast doubt on the most compelling evidence for a devastating tsunami. Speaking this week at the American Institute of Archaeology meeting in New Orleans, geoarchaeologist Rachel Kulick of the University of Toronto announced the preliminary results of her fieldwork at Palaikastro, the site of a major Minoan town on Crete’s northeastern coast. Kulick’s work reopens the tsunami question and deepens the mystery surrounding Thera’s toll on the Minoans 3,500 years ago.

This mega-tsunami scenario has been an irresistible theme for popular writers and TV shows, since it seems to echo the story of Atlantis recounted by the philosopher Plato. In his fanciful tale, Atlantis, a giant island continent, was the center of an advanced civilization until the ocean swallowed it up in a single day and night. Perhaps the fate of the Minoans conjured up the Atlantis legend.

In 1939, leading Greek archaeologist Spyridon Marinatos was the first to suggest that Thera’s eruption doomed the Bronze Age Minoans, who created Europe’s first great civilization on the island of Crete, only 70 miles south. Ash flows and landslides may have triggered huge tsunamis, which could have swamped Cretan ports and wiped out the Minoan trading fleet.

Palaikastro has been the focus of a major excavation project since the 1980s, supported by the British School at Athens and the Greek Ministry of Culture. The dig has unearthed seven blocks of the Minoan town, originally consisting of substantial two-story houses arranged in a tidy network of paved and drained streets. In 2001, the project invited geoarchaeologist Hendrik Bruins from Ben Gurion University to investigate an unusual soil layer about 300 feet northeast of the town, exposed in a sandy cliff side overlooking the present-day beach.

When Bruins showed me this layer in 2006, I saw a thick layer containing a chaotic jumble of broken Minoan pottery, rocks, lumps of grey volcanic ash, and mashed-up animal teeth and bones. It looked as if a giant fist had smashed through an ancient neighborhood and then dumped the churned-up refuse on the beach with great force. While a violent storm surge could have been responsible, Bruins carried out careful tests that implicated a tsunami generated by Thera’s eruption. Radiocarbon dating of seashells and cattle bones, and chemical fingerprinting of the ash, all seemed to check out. What’s more, volcanic ash found in one of the streets in the Minoan town had evidently been washed in by water. With the help of computer simulations run by a leading tsunami expert, Bruins and his colleagues concluded that a giant wave—at least 30 feet high—had swept into the bay and deluged the town.

A chaotic layer of animal bones, ash, and Minoan pottery exposed in the side of a cliff overlooking the beach at Palaikastro, identified by Hendrik Bruins and his colleagues as evidence for a massive tsunami.

This research, published in 2008 and 2009, won wide media attention. A leading expert on ancient volcanoes, Clive Oppenheimer of the University of Cambridge, described the work as meticulous and providing “a strong case.”

But last summer, Rachel Kulick began questioning the study’s conclusions when she carried out an intensive analysis of soil blocks that had been saved from earlier digs in the Minoan town. If a tsunami had surged into the town, the same chaotic mixing of materials should have been obvious in these layers as in the cliffside at the beach. But under the microscope, the soil and ash layers looked very different. The ash from Thera had fallen in many fine layers just above the surface of the Minoan street. There were signs of gentle water action, perhaps by rain, but it had not been enough to disturb the ash layers or churn up the underlying paved street, as a tsunami almost certainly would have done.

Another new soil section dug last summer told the same story. The location of this section—a major, 13-foot-deep sample—is particularly significant. It comes from a relatively low elevation compared with the rest of the site, so if a massive incoming wave had crashed across town, it should certainly have registered in the layers there.

“But there is no evidence of a high energy water event in the section,” Kulick said, “only sand and gravel deposited by ordinary processes of drainage and erosion.” These negative findings from the town suggest there must be another explanation for the chaotic layers at the beach—perhaps a storm surge that disturbed Minoan refuse pits in a neighborhood now lost to the sea. Whatever had transpired to disrupt the remains at the coast had apparently not been powerful enough to penetrate inland and seriously damage the Minoan town.

Next summer’s dig, directed by Carl Knappett of the University of Toronto, will provide another opportunity to check out these preliminary findings. But if Kulick is right, then Palaikastro would join a long list of at least 40 Minoan sites where efforts to identify tsunami layers have proven frustratingly elusive. The most convincing tsunami deposits yet found have come from the sea floor southeast of Santorini and from Bronze Age sites on the Turkish coast. So it’s possible that destructive waves were mainly focused eastward, away from Crete.

A similar story applies to Thera’s plume of destructive ash. At the time of the eruption, the wind was evidently blowing toward the southeast, so much of Crete escaped the ash fall, while Palaikastro received a relatively light dusting of around two to four inches. However, even this amount would have had serious consequences, choking wells and poisoning pastures and olive groves. At Palaikastro, new wells were dug and parts of the site were abandoned and rebuilt. But what was Thera’s long-term impact on the Minoan world?

A microscope thin section of soil from the Palaikastro excavations shows a grey lump of ash from the Thera eruption.

According to one influential view, the traumatic effects of the eruption may have triggered religious and social unrest out of all proportion to any physical damage. Perhaps that led to increasing internal conflict and a gradual unraveling of the Minoan world. The emphasis is on “gradual,” since the record is clear that their brilliant civilization continued for another century or so; in fact, some of the most famous works of Minoan art and architecture post-date the eruption.

Science will continue to clarify the picture of what happened to the Minoans, but many archaeologists argue that we too readily underestimate the resilience of ancient peoples in the face of natural disaster and oversimplify the stories we tell about the fate of ancient peoples.