glacialoutburst

A glacial outburst, also known as a glacier lake outburst flood (GLOF) or, in Icelandic, a jökulhlaup, is a rapid release of freshwater that has been stored behind a glacier dam or subglacial reservoir. The flood can transport large volumes of ice, sediment, and rock as it travels downstream, sometimes over long distances and into inhabited or economically important areas.

Causes of glacial outbursts include the failure or breach of an ice dam that holds back meltwater in supraglacial or proglacial lakes; the release of subglacial lakes through hydrofracturing or increased pressure; geothermal or volcanic heat melting channels under the ice and creating pathways for sudden drainage; and erosion or structural failure of moraine dams. These mechanisms can act alone or in combination, sometimes triggered by volcanic activity beneath a glacier or by rapid changes in meltwater input.

Characteristics of glacial outbursts include very high discharge rates, often ranging from thousands of cubic meters per second, with durations from several hours to days. The flows are typically highly turbid and debris-laden, and can cause rapid river level rises, downstream flooding, channel incision, and sediment deposition. The paths of outbursts can change as channels scoured by floods reconfigure.

Impacts and management: glacial outbursts threaten infrastructure such as roads, bridges, hydropower facilities, and communities downstream. Risk reduction relies on monitoring lake levels and dam stability, early warning systems, flood-routing infrastructure, and, where possible, controlled drainage or diversion of water.

Examples occur in glacierized regions worldwide, including Iceland, the Himalayas, the Andes, and parts of Alaska, with monitoring drawing on satellite data, seismic networks, and hydrological gauges.