jökulhlaup A sudden, violent, but short-lived increase in the discharge of a melt-water stream issuing from a glacier or ice cap, sometimes owing to volcanic activity beneath. A lake may develop above the heat source; this is subsequently breached to produce a torrent of melt-water (e.g. Lake Grimsvotn on Vatnajökull, Iceland). Flow velocity may reach 7–8 m/s and the discharge may attain 100 000 m³/s (e.g. the Katlahlaups from Myrdalsjökull, Iceland), comparable to rates of flow of the Amazon river.

jökulhlaup Sudden, violent, but shortlived increase in the discharge of a meltwater stream issuing from a glacier or ice-cap, sometimes due to volcanic activity beneath. A lake may develop above the heat source; this is subsequently breached to produce a torrent of meltwater, e.g. Lake Grimsvotn on Vatnajökull, Iceland. Flow velocity may reach 7–8 m/s and the discharge may attain 100 000 m³/s (e.g. the Katlahlaups from Myrdalsjökull, Iceland), comparable to rates of flow of the Amazon river.