Flooding due to the outburst of a glacier lake. A glacier lake outburst flood occurs when a lake — dammed by a glacier or a terminal moraine - fails. The outburst can be triggered by erosion, a critical water pressure, a mass movement, an earthquake or cryoseism. A jökulhlaup is a special type of a glacier lake outburst flood related to the outburst of an ice-dammed lake during a volcanic eruption