Eruption delivered hammer blow to the Norse gods

If Thor had to die, this, surely, is how he would have wanted to go. Across Europe, the skies turned blood-red. Famine, drought and pestilence stalked Eurasia. In Egypt, the Nile failed to flood, in China there was a great freeze.

And in Iceland itself, Norse writings record a terrible event. "The Sun starts to turn black, land sinks into the sea . . . flame flies high against heaven itself." With that farewell, the pagan gods began to leave the island.

A team of geographers and historians has used ice cores to date a spectacular eruption in Iceland to AD939. They have also argued that the eruption of the Eldgja (fire gorge), which lasted over a year, probably became the source of one of the most famous Icelandic poems of the time. This poem, Voluspa, described an event that preceded the destruction of the pagan pantheon and the arrival of Christianity.

The eruption more than fitted the bill. "Huge fire fountains would have risen kilometres into the sky," said Clive Oppenheimer, from Cambridge University. "There would have been voluminous lava flows, spread over the regions where Icelanders had livestock and farms."

Beneath the glaciers, where fire met ice, there would have been violent explosions. Elsewhere, rain fell as acid.

Taken together it would have been enough to make anyone question their gods. But did they? Although the eruption was known to have occurred after settlement in 874, no one knew exactly when. However, Oppenheimer, in a paper for Climatic Change, has dated it precisely. Using the known date of an eruption in North Korea, 946, he could count down seven years through the Greenland ice record to find ash from the Eldgja. That was when he spoke to a colleague, who studied Norse literature.

Andy Orchard, from Oxford University, suggested that Voluspa can be dated to just after this event and contained exactly the kind of apocalyptic imagery associated with an eruption. One verse in particular struck him. "[The wolf] is filled with the life blood of doomed men, reddens the powers’ dwellings with ruddy gore; the sun beams turn black the following summers, weather all woeful".

The poem then talks about steam spurting and flames shooting into the sky. For a people used to volcanic activity, this suggested no ordinary eruption.

Connecting the eruption to this poem was doubly significant though, because Voluspa was the text used as tenth century propaganda to Christianise Iceland. It begins with Odin seeking a prophecy, ends with all the old gods dead in battle and promises a new, single god to replace the pantheon and bring renewal. "It ties them in to a pagan past of Odin and Thor," said Orchard, ‘‘But also looks forward to the coming of a new god who is going to be the one great god who will bring peace and stability." At the turn of the first millennium, within living memory of the Eldgja eruption, the island converted to Christianity.