<P> The name Mongibel is found in Arthurian Romance, as the name of the otherworld castle (or realm) of Morgan le Fay and her half - brother, King Arthur, localised at Etna, according to traditions concerning them derived from the stories told by the Breton conteurs who accompanied the Norman occupiers of Sicily . What were originally Welsh conceptions concerning a dwarf king of a paradisal, Celtic underworld became attached to the quasi-historic figure of Arthur as "Ruler of the Antipodes" and were then transplanted into a Sicilian milieu, by Bretons impressed by the already 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 the location of Arthur's kingdom . </P> <P> The Fada de Gibel of the Castle of Gibaldar (Fairy of Etna) appears in Jaufre, the only surviving Arthurian romance in the Occitan language, the composition of which is dated to between 1180 and 1230 . However, in Jaufre, while it is clear from her name that the fairy queen in question is Morgan le Fay, the rich underworld queendom of which she is the mistress is accessed, not through a fiery grotto on the slopes of Etna, but through a' fountain' (i.e., a spring)--a circumstance more in keeping with Morgan's original watery, rather than fiery, associations, before her incorporation into the folklore of Sicily . For another Sicilian conception of the fairy realm or castle of Morgan le Fay--see Fata Morgana (mirage) re . an optical phenomenon common in the Strait of Messina . </P> <P> Volcanic activity first took place at Etna about 500,000 years ago, with eruptions occurring beneath the sea off the ancient coastline of Sicily . About 300,000 years ago, volcanism began occurring to the southwest of the summit (centre top of volcano) then, before activity moved towards the present centre 170,000 years ago . Eruptions at this time built up the first major 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 . </P> <P> 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, 800 km (497 mi) to the north . </P>

When was the first time mount etna erupted