Iceland's conversion to Christianity was thanks, in part, to a volcanic eruption, according to researchers from the University of Cambridge.

The Eldgjá volcano in southern Iceland erupted 1,000 years ago, covering the entire island with 20cm of lava.

The study, led by Clive Oppenheimer of Cambridge University, concluded the explosion 'began around the spring of 939 [CE] and continued at least through the autumn of 940 [CE]'.

The researchers compared scientific evidence from ice cores and tree rings to correlate the time when the largest lava flow in Iceland's history occurred with the country's most celebrated medieval poem, Vǫluspá, which was written at least as far back as 961 CE.

The poem describes the aftermath of the eruption with cold summers caused by volcanic ash restricting sunlight and the consequent death of livestock. It also used apocalyptic language to describe the events as bringing about the the exit of the many pagan gods, and the coming of one God. 

'The poem's interpretation as a prophecy of the end of the pagan gods and their replacement by the one, singular god, suggests that memories of this terrible volcanic eruption were purposefully provoked to stimulate the Christianisation of Iceland,' Oppenheimer said on Monday.

The research, published online, added: 'The end of the pagan pantheon is foretold in Iceland's renowned medieval poem, Vǫluspá ('the prophecy of the seeress'). Several lines of the poem describe dramatic eruptive activity and attendant meteorological effects in an allusion to the fiery terminus of the pagan gods.

'We suggest that they draw on first-hand experiences of the Eldgjá eruption and that this retrospection of harrowing volcanic events in the poem was intentional, with the purpose of stimulating Iceland's Christianisation over the latter half of the tenth century.'