Glacier run

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The break of the Hubbard Glacier
World map: Overview of places of glacier runs

A glacier run (outdated: glacier lake eruptions) is the term used to describe the sudden emptying of a lake under a glacier in the form of tidal waves caused by natural processes .

term

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

This term is very common in Iceland , especially in the south of the country, where numerous, often catastrophic glacier runs have been experienced, triggered by volcanoes located under glaciers .

Forms of origin: high temperature areas and volcanic eruptions

The typical courses of glaciers in volcanic areas arise either from the constant thawing of the glacier over a high temperature area or when a volcano covered by a glacier erupts.

High-temperature areas below glaciers continuously melt the glaciers above them. The water collects in basins or in the form of bubbles. When its volume exceeds a certain limit, it breaks through the ice barrier in front of it and a mostly not very significant tidal wave pours at regular intervals through low-lying valleys into the sea, e.g. B. about every 2 to 3 years in the Skaftá river in Iceland, whereby about flow rates of 2,000 to 5,000 m³ / s are produced, as well as regular thawing processes over the geothermal area of Grímsvötn every 4 to 5 years.

Much more significant and unpredictable, on the other hand, are the glaciers created by volcanic eruptions .

The heat of the eruption melts part of the ice cap over the volcano. The water often gathers in a lake under the now thinner ice sheet. If the tidal wave, consisting of water, pieces of ice of various sizes and sediments, breaks through the upstream ice barrier, the lake empties in a short time and the floods pour into the sea over lower valleys and plains.

The glacier water runs off through tunnels under the ice cover or it is distributed under the ice over larger areas until it then emerges at the edges of the glacier. The exact course is influenced by factors such as ice thickness, slope and water temperature.

The phenomenon resembles the lahars of volcanic surfaces that are not covered by ice.

1996 Glacier Run in South Iceland

Glacier run on Skeiðarársandur 1996

The last major glacier run occurred in 1996 on the Skeiðará river due to an eruption in the Grímsvötn volcanic system . Gjálp volcano, 10 km from the central volcano , erupted in October and melted a lot of ice. The meltwater flowed into the subglacial lakes Grímsvötn below, which are located above the central volcano itself.

The water level of the Grímsvötn lakes had been precisely measured, and so the timing of the flooding of the plains below could be predicted with relative accuracy. The south east-west traffic connection running across these levels, Ringstrasse 1 , was closed in good time so that no people were harmed. The glacier run of 1996 reached a volume of up to 45,000 m³ of water per second and tore away parts of the ring road and a bridge with it. Ice blocks up to ten meters high were also transported and, after the end of the glacier run, lay in the Skeiðarársandur plains .

Katla and Mýrdalsjökull

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

Glacier runs in other parts of the world

Especially in all areas where volcanism and glaciers meet, there is also the danger of glacier runs, e.g. B. also in Alaska , New Zealand , Chile , on the Kamchatka Peninsula etc.

Non-volcanic causes

The term is also used for other flooding events that are related to glaciers, for example when a terminal moraine can no longer withstand the dammed water masses or when the ice prevents the emptying of a lake adjacent to the glacier and breaks due to the water pressure.

An example would be the 2002 break of the Hubbard Glacier , which cut off the Russell Fjord from Disenchantment Bay . This was the second largest man-documented glacier run. Another example would be the fairly regular drainage of the glacial lakes on the Tulsequah Glacier in British Columbia, Canada.

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Individual evidence

  1. ↑ HUSchmid: English-Icelandic German. Hamburg (Buske) 2001, p. 123
  2. ↑ HU Schmid, ibid., P. 107
  3. ↑ cf. also Ari Trausti Guðmundsson, Halldór Kjartansson: Land im Werden. An outline of the geology of Iceland. Reykjavík (Vaka-Helgafell) 1996, p. 40
  4. ↑ cf. http://www.jardvis.hi.is/page/jhskaftarkatlar Accessed January 1, 2011
  5. ↑ cf. Ari Trausti Guðmundsson: Living Earth. Facets of the geology of Iceland. Reykjavík (Mál og Menning) 2007, p. 238
  6. ^ Ari Trausti Guðmundsson, 2007, ibid.
  7. ↑ cf. http://wayback.vefsafn.is/wayback/20050622000000/www.earthice.hi.is/page/ies_gjalp1996 Accessed January 1, 2011
  8. ↑ cf. http://wayback.vefsafn.is/wayback/20051102000000/www.earthice.hi.is/page/ies_katla1918 Accessed January 1, 2011
  9. ↑ cf. http://wayback.vefsafn.is/wayback/20100330000000/www.earthice.hi.is/page/ies_katlamonitoring Accessed January 1, 2011
  10. ^ Ari Trausti Guðmundsson, 2007, p. 238
  11. ^ Second-Largest Glacial Flood Worldwide in Historic Times Occurs as Russell Lake Glacier Dam Ruptures (USGS, August 16, 2002) Accessed January 1, 2011
  12. ↑ Archive link ( Memento of the original from May 27, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Accessed January 1, 2011  @1@ 2Template: Webachiv / IABot / pajk.arh.noaa.gov