Jökulhlaup
U.S. National Park Service photo (fair use policy)
A jökulhlaup is a glacial outburst flood, something that happens when a moving glacier forms a dam. Because ice makes a poor dam, being lighter and softer than rock, the water behind the dam eventually breaks through. This example is from Yakutat Bay in southeastern Alaska. Hubbard Glacier pushed forward in the summer of 2002, blocking the mouth of Russell Fiord. The water level in the fjord began to rise, reaching 18 meters above sea level in about 10 weeks. On 14 August the water burst through the glacier and ripped out this channel, about 100 meters wide.
Jökulhlaup is a hard-to-pronounce Icelandic word meaning glacier burst; English speakers say it "yokel-lowp" and people from Iceland know what we mean. In that land of ice and fire, jökulhlaups are familiar and significant hazards. The Alaskan one just put on a good show—this time. A series of gigantic jökulhlaups transformed the Pacific Northwest, leaving behind the great Channeled Scabland, in the late Pleistocene; others occurred in central Asia and the Himalayas at that time. (Read more about jökulhlaups)
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Geologic Features and Processes
Glaciers and Ice
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