ABOUT 140 generations ago, a massive explosion shook the Aegean island of Thira (Santorini). It was probably audible as far away as modern Iraq or Southern France. The island, including its capital at Akrotiri - hitherto a bustling centre of Aegean trade and in close contact with the great Minoan palaces of Crete, but also with Egypt and the Near East - was buried under up to 50 metres of ash and rock.

Tsunamis devastated much of the Aegean, especially the densely settled northern coast of Crete. Ash rained down on distant areas like Turkey and Crete. A plume of smoke rose tens of kilometres into the air, blowing enormous amounts of dust into the stratosphere and thus affecting the global climate for months or years to come.

More than 2,500 years later, a middle-aged Danish professor stood halfway up the steep edge of the caldera, the crater that now defines the inside of the C-shaped island of Santorini. Awkwardly perched on a ladder placed on the rubble eroding from the cliffs, he was trying to peer into a smallish hole in the cliff face itself. He suspected that a piece of wood just visible in that hollow could help him answer a key question: When exactly did the island explode?

On December 1, the Danish Archaeological Institute hosted a lecture by professors Walter Friedrich (University of Aarhus, Earth Sciences Department) and Walter Kutschera (University of Vienna, Department of Physics) entitled "The Puzzle of Dating the Minoan Eruption - News from Santorini and Egypt". It was the first time that their new, still highly controversial proposal (originally published in Science Magazine in 2006) for the dating of the so-called Minoan eruption was presented in Athens.

That event has long been recognised as a linchpin of Greek prehistory. At some point around the middle of the 2nd millennium BC, during the heyday of the Minoan civilisation of Crete, which controlled much of the Aegean coasts and islands, the long-dormant volcano of Thira erupted. The explosion is estimated to have been 10 times as violent as the famous Krakatoa event (1883, in Indonesia) and stronger than the 1815 eruption of Mount Tambora (Indonesia), which blew so much dust into the atmosphere that it led to a two-year global climate cooling, an event remembered in Europe and North America as "the year without a summer".

Although we do not know exactly what effects the eruption had, apart from burying the now-famous Bronze Age town of Akrotiri, it must have been a devastating blow to the Minoan world, causing tsunamis and weakening the sea-borne power of Crete. Although Minoan culture survived for several more generations, it has been speculated that the end of that civilisation was triggered by the event. More fancifully, some have tried to recognise the origins of the Classical legend of Atlantis in it.