Jökulhlaup

As a glacier run is defined as the sudden caused by natural processes emptying a located below a glacial lake in the form of tidal waves.

• 4.1 The concept
• 4.2 Examples

Term glacier run

The term glacier run is a literal translation of the Icelandic term Jökulhlaup. Isl Jökull in German means glaciers, isl. hlaup is running; Clot.

This term is very common in Iceland, as it vA has experienced numerous often catastrophic glacier runs to the south of the country, there were triggered by lying under glaciers volcanoes.

Glacial cycles caused by volcanism

Emergence of forms: high-temperature areas and volcanic eruptions

The typical glacier runs in volcanic regions are formed either by continuous melting of the glacier via a high-temperature area, or when a from a glacier -covered volcano erupts.

Situated beneath glaciers high temperature areas continuously melt from the glaciers located above them. The water collects in pools or in the form of bubbles. If its volume exceeds a certain limit, it breaks the ice barrier in front of it and usually not very significant tidal wave pours into regular intervals by low-lying valleys to the sea, such as approximately every 2 to 3 years in the river Skaftá in Iceland, with about flow rates from 2,000 to 5,000 m³ / s are produced, as well as of regular thawing above the geothermal area of Grímsvötn every 4 to 5 years

Far more significant, and unpredictable, however, are caused by volcanic eruptions, glacier runs.

The heat of the eruption melts a portion of the ice cap on the Volcano. Water collects often in a lake under the ice cover now thinner. Breaks, which consists of water, ice cubes of various magnitude and sediment tidal wave, the upstream ice barrier, the lake drained in a short time and the floods rush down below location valleys and plains into the sea.

The glacier water running from it through tunnels under the ice or it is distributed under the ice on more important areas, until it occurs at the edges of the glacier into the open. The exact course is also influenced by factors such as ice thickness, slope and water temperature.

The phenomenon is similar to the lahars in non- ice-covered surfaces of volcanoes.

Glacier run in 1996 in South Iceland

1996 The last major glacier run occurred on river Skeiðará due to an outbreak in the volcanic system of Grímsvötn. The 10 km from the central volcano remote volcano Gjálp broke out in October and had melted a lot of ice. The melt water flowed into the subglacial lakes located beneath Grímsvötn, located above the central volcano itself.

One had the water level of the Grímsvötn lakes measured accurately so you could the timing of flooding including situated levels predict relatively accurately. The running of these levels southern east-west transport connection, the Ringstrasse 1, could in time be locked so that no people were harmed. The glacier run in 1996 after all, reached a volume of up to 45,000 cubic meters of water per second and ripped parts of the ring road and a bridge away with it. Up to ten meter high blocks of ice were transported and were after the end of the glacier run in the outwash plain Skeiðarársandur.

Katla and Mýrdalsjökull

Also known for its glacier runs is located in the extreme south of Iceland Mýrdalsjökull with the volcano Katla underneath. It is continuously monitored.

Glacier runs in other parts of the world

Especially in all areas where volcanic activity and glaciers meet, there is also the danger of glacial streams, eg also in Alaska, New Zealand, Chile, on the Kamchatka Peninsula, etc.

Nichtvulkanische causes

The term is also used for other flooding events that are associated with glaciers, such as when a terminal moraine no longer withstand the dammed water masses, or when the ice prevents the draining of an adjacent to the glacier lake and breaks by the water pressure.

One example is the 2002 was fracture of the Hubbard Glacier, had the Russell Fjord cut off from Disenchantment Bay. This was the second largest recorded human glacier run .. Another example would be the fairly regular emptying of glacial lakes on Tulsequah Glacier, also in Alaska.