Mount Etna otherworldly associations of the great, volcanic mountain of their new home. Mediaevalist Roger Sherman Loomis quotes passages from the works of Gervase of Tilbury and Caesarius of Heisterbach (dating from the late twelfth century) featuring accounts of Arthur's returning of a lost horse which had strayed into his subterranean kingdom beneath Etna. Caesarius quotes as his authority for the story a certain canon Godescalcus of Bonn, who considered it a matter of historic fact of the time of Emperor Henry's conquest of Sicily "circa" 1194. Caesarius employs in his account the Latin phrase "in monte Gyber" ("within Etna") to describe
Mount Etna volcanic edifice, forming a stratovolcano in alternating explosive and effusive eruptions. The growth of the mountain was occasionally interrupted by major eruptions, leading to the collapse of the summit to form calderas. From about 35,000 to 15,000 years ago, Etna experienced some highly explosive eruptions, generating large pyroclastic flows, which left extensive ignimbrite deposits. Ash from these eruptions has been found as far away as south of Rome's border, to the north. Thousands of years ago, the eastern flank of the mountain experienced a catastrophic collapse, generating an enormous landslide in an event similar to that seen in the 1980