The Prose Edda 1.4

Gangleri said: "What was the beginning, or how began it, or what was before it?" Hárr answered: "As is told in Völuspá:

Erst was the age when nothing was: Nor sand nor sea, nor chilling stream-waves; Earth was not found, nor Ether-Heaven,— A Yawning Gap, but grass was none."

Then said Jafnhárr: "It was many ages before the earth was shaped that the Mist-World was made; and midmost within it lies the well that is called Hvergelmir, from which spring the rivers called Svöl, Gunnthrá, Fjörm, Fimbulthul, Slídr and Hríd, Sylgr and Ylgr, Víd, Leiptr; Gjöll is hard by Hel-gates." And Thridi said: "Yet first was the world in the southern region, which was named Múspell; it is light and hot; that region is glowing and burning, and impassable to such as are outlanders and have not their holdings there. He who sits there at the land's-end, to defend the land, is called Surtr; he brandishes a flaming sword, and at the end of the world he shall go forth and harry, and overcome all the gods, and burn all the world with fire; thus is said in Völuspá:

Surtr fares from the south with switch-eating flame,— On his sword shimmers the sun of the War-Gods; The rock-crags crash; the fiends are reeling; Heroes tread Hel-way; Heaven is cloven."