Ásbyrgi Canyon was formed by catastrophic glacial outburst floods several thousands of years ago. These floods arose from meltwater from volcanic eruptions under the Vatnajökull ice cap, flowing down the Jökulsá á Fjöllum river. Alternatively,Icelandic legend says that the canyon was formed by a hoof-print of Odin's 8-legged horse Sleipnir as they passed over the land.