Katla is one of the largest volcanoes in Iceland and a difficult neighbour. The broad summit is buried under Myrdalsjokull glacier's thick, icy blanket. When Katla starts to simmer, the threat of a powerful eruption under the ice develops. An eruption causes a glacial burst, forcing a vast quantity of melt water out from under the ice. It doesn't last long but the volume of water in the resulting catastrophic flood can reach an average flow rate equal to that of the largest river in the world, the Amazon.

Katla happened to be the name of the housekeeper in the farming settlement of Thykkvabaejarklaustur. She was a well-known personality and possessed a pair of trousers that would allow anyone who wore them to run without getting tired. One autumn day, Katla came home to discover that Bardi, a shepherd working on the farm, had stolen her trousers to use during the sheep roundup. As punishment, Katla drowned Bardi in a tub of sour whey. As winter approached and the whey began to run out, Katla was heard to mutter to herself "Bardi will appear soon". When Bardi's fate was indeed revealed, Katla jumped into her trousers, ran up onto the glacier and then threw herself into a chasm that's now known as Katla Fissure. Katla was never seen again. But shortly after she disappeared, an eruption occurred under the Myrdalsjokull glacier, causing a glacial burst that swept over the lowland plain and destroyed the settlements of Dynskogahverfi and Lageyjahverfi to create a sandy wasteland that's now called Kotlusandur or Myrdalssandur. The volcano sends a reminder of its sinister past every 80 years or so, usually erupting in the autumn.