Jökulhlaups: their associated landforms and landscape impacts

Abstract: Glacial outburst floods also known as jökulhlaups are important features connected with glaciers globally. They may induce catastrophic floods as well as new landforms. This review describes and synthesizes jökulhlaup trigger mechanisms as well as associated landforms and landscape impacts of jökulhlaups with a special focus on Skeiðarársandur, south Iceland, and the 1996 jökulhlaup. Important sources of water for jökulhlaups are rapid melting of glacier ice, heavy rainfall, and most importantly the release of stored water from glacial lakes. The release of water may be due to three main initiating processes; overspilling, failure of the dam or changes in the hydraulic pressure. Some scholars divide them into further categories depending on their drainage mechanism. It is quite hard to draw a strict line between what should be classified as only jökulhlaup induced landforms and what should not. There is one landform that is mentioned together with jökulhlaups more than any other and this is the sandur or the glacial outwash plain. An abnormally large fissure eruption in conjunction with storage of melt water that exceeded the usual threshold for drainage from the lake Grímsvötn made the 1996 jökulhlaup at Skeiðarársandur to an unusually large event.