What Icelandic term means a glacial outburst flood?

The Icelandic term for a glacial outburst flood is jökulhlaup.

The word literally means “glacial run”: jökull means glacier, while hlaup refers to running or a flood. It originally described sudden floods from beneath Iceland’s Vatnajökull ice cap, often triggered by geothermal heating or volcanic eruptions beneath the ice.

Today, glaciologists use jökulhlaup more broadly for abrupt releases of water from subglacial or proglacial lakes. The water may accumulate beneath thick ice, behind an ice dam, or in a depression formed by geothermal activity. Once pressure overcomes the drainage route, discharge can rise dramatically.

Jökulhlaups are easily confused with ordinary glacial meltwater floods and with lahars. A lahar is a volcanic mudflow made from water mixed with ash and debris, whereas a jökulhlaup specifically emphasizes the sudden release of glacier-associated water. Iceland’s Katla and Grímsvötn volcanoes are especially well known for producing them.