The study contradicts earlier explanations that the tsunami must have been the result of a caldera collapse, which occurs when the crust above a volcano’s magma chamber slips swiftly downward as the chamber empties during an eruption. At Santorini, the thinking went, much of the island — the caldera was huge — sank suddenly into the Aegean, triggering the tsunami.

The new data suggests that the caldera was cut off from the sea. “When the caldera collapsed, it was isolated — there was no water inside,” said Paraskevi Nomikou, a geologist at the National and Kapodistrian University of Athens and the lead author of the study in Nature Communications.