The volcano that destroyed Thera erupted roughly 3,500 years ago. Some scholars believe that this massive volcanic blast, one of the strongest in recorded history, was responsible for wiping out Minoan culture, on the island of Crete, directly to the south. And Professor Hans Goedicke, of Johns Hopkins University, goes so far as to argue that the eruption caused a massive tidal-like wave that traversed the Mediterranean, drowned the Egyptian army that was in hot pursuit of the fleeing Israelites during the Exodus and was forever preserved in the Bible as the parting of the Red Sea.

But just when did the volcano erupt?

That’s the crucial question. Goedicke’s scenario, for example, calls for the blast and ensuing tidal wave to have taken place in 1477 B.C., the date required by a pharaonic inscription that he claims describes the same events (albeit from the other side) as the Biblical account of the Red Sea. Until recently, the commonly accepted dating for the volcano’s eruption has been between 1550 and 1500 B.C., seemingly close enough to the 1477 B.C. date proposed by Goedicke.

New evidence, however, from some surprising sources, is creating something of a tidal wave itself—one that threatens to leave Goedicke’s theory in its wake. Dendrochronologists (scienfists who study the rings of ancient trees whose lifespans overlap) have noted narrow growth rings among oaks in Ireland’s bogs for the decade following 1628 B.C. They believe the dust spewed forth by the Thera volcano caused a period of worldwide cooling that stunted tree growth. Fellow dendrochronologists in the United States reached the same conclusion by studying bristlecone pines in California. If this occurred in 1628 B.C. or thereabouts, it is too early to be linked to the Exodus, even by Goedicke’s reckoning.

A late 17th-century B.C. date for the eruption of the Thera volcano is backed up by research in another field. In 1987 Danish geologists examining signs of volcanic acidity in the Greenland ice sheet concluded that the Thera volcano erupted in 1645 B.C., give or take 20 years. Most persuasive of all is the radiocarbon dating conducted by University of Pennsylvania scientists on seeds and wood found in volcanic ash on Thera itself. The researchers put the eruption at no later than 1600 B.C.

The best evidence so far, in sum, has the blast occurring 150 years too early to mesh with Goedicke’s timetable.