Hraunfossar is a series of waterfalls formed by rivulets streaming over a distance of about 3,000 feet out of the Hallmundarhraun lava field which flowed from an eruption of one of the volcanoes lying under the glacier Langjökull. The waterfalls pour into the Hvítá river from ledges of less porous rock in the lava. The name comes from the Icelandic word for lava (hraun) and the word for waterfalls (fossar).