Icelandic term "Jökulhlaup" - a glacial outburst flood.

Jökulhlaup is an Icelandic term that refers to a glacial outburst flood. It occurs when water accumulates beneath a glacier and is suddenly released, resulting in a rapid and powerful flood. Jökulhlaups are typically triggered by volcanic activity, subglacial eruptions, or the melting of ice due to geothermal heat.

The process leading to a jökulhlaup begins when water accumulates in subglacial lakes or channels beneath a glacier. This water can come from melting ice or from geothermal sources that provide heat to melt the ice. As the water volume increases, pressure builds up until it exceeds the strength of the ice holding it back. This causes the ice to rupture, resulting in a sudden release of water from beneath the glacier.

The unleashed floodwater flows rapidly down the glacier's surface, carrying large amounts of sediment, rocks, and ice. Jökulhlaups can be incredibly powerful, with floodwaters reaching high velocities and carrying significant amounts of debris. The floods can cause erosion, alter river courses, and deposit sediment over large areas downstream.