A
glacial lake outburst flood (GLOF) is a type of
outburst flood that occurs when the dam containing a glacial lake fails. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, is called a
Jökulhlaup. The dam can consist of
glacier ice or a
terminal moraine. Failure can happen due to
erosion, a buildup of
water pressure, an
avalanche of rock or heavy snow, an
earthquake or
cryoseism,
volcanic eruptions under the ice, or if a large enough portion of a glacier breaks off and massively displaces the waters in a glacial lake at its base.