Is Ragnarök an ancient pagan prophecy, a Christian borrowing, or a memory of volcanoes?

Ragnarök is the Norse end of the world, and where it comes from is an open debate. In the sources it is a foretold series of events: a great battle in which Odin, Thor, Týr, Freyr, Heimdall and Loki perish, catastrophic natural disasters including the burning of the world, and finally the submersion of the world underwater. Then the world rises again, cleansed and fertile, and two human survivors, Líf and Lífþrasir, repopulate it.

The main source is the poem Völuspá, in which a seeress tells Odin the creation, end and rebirth of the world. It dates to the tenth century, the century before Iceland became Christian. That timing fuels the first theory: some scholars hold that there are Christian influences, noting parallels with the Sibylline Prophecies, and the Christian Last Judgment of the Book of Revelation is similar in imagery, with a final cosmic conflict, devastation and renewal.

The second theory points the other way, to deep roots. Parallels with the beliefs of other Indo-European peoples have led some to see Ragnarök as a later evolution of a Proto-Indo-European belief.

The third theory is volcanic. Hilda Ellis Davidson suggested that the sun turning black, steam rising and flames touching the heavens may be inspired by Icelandic eruptions. In 2018 Cambridge researchers suggested that Völuspá, estimated to date from 961, was a roughly contemporary chronicle of the 939 eruption of Eldgjá, its imagery used purposefully to accelerate the Christianization of Iceland.