Jökulhlaups (an Icelandic word pronounced yo-KOOL-lahp) are glacial outburst floods. They occur when a lake fed by glacial meltwater breaches its dam and drains catastrophically. These lakes can take a number of forms:
- Ice dammed lakes that are held in by the glacier ice itself
- Moraine, rock, or sediment dammed lakes
- Lakes that lie form beneath glaciers
In order for a jökulhlaup to occur, the lake water levels must reach a critical point such that the lake:
- Causes its ice dam to float
- Overtops its dam, causing rapid incision into the sediment, rock, or ice that contains it
- Carves large meltwater channels beneath the glacier ice that allow for rapid drainage
Jökulhlaups may occur with a somewhat regular periodicity, but others drain without warning.
To learn more about glaciers, glacier features, and glacial landforms, see the Glaciers & Glacial Landforms Page.