Commentary Par VIII 70

Tifeo (Typhon [or Typhoeus]), also referred to by the variant Tifo [[Inf XXXI 124]]), was a hundred-headed monster who attempted to acquire power over all creatures. Jupiter struck him down with his thunderbolt and buried him in Tartarus under Mt. Aetna, the eruptions of which were supposedly due to his exertions to escape (see Ovid, Metam. V.346-358, where Typhon's two hands are said to be pilloried by Pelorus and Pachynus). Dante dispenses with 'classical erudition' in the name of 'modern science': The clouds of smoke hanging over the area are not the result of Typhon's struggles to escape, but of sulphur burning in the earth. For this explanation, Tozer (DDP Tozer.Par.VIII.72) suggests that Dante found a source in Isidore of Seville (Etym. XIV.8).