Grímsvötn

Infobox Mountain
Name = Grímsvötn
Photo = grimsvotn sat.jpg
Caption = Ash from Grímsvötn volcano across Vatnajökull ice cap, November 7, 2004
Elevation = 1,725 m (5,659 ft)
Coordinates = coord|64.42|N|17.33|W|type:mountain
Location = Austur-Skaftafellssýsla / Vestur-Skaftafellssýsla, ISL
Type = volcanic caldera
Last eruption = 2004. The location of the lakes is coord|64|25|N|17|20|W|, at an elevation of 1,725 m (5,659 ft).

Grímsvötn has a southwest-northeast-trending fissure system, and the massive climate-impacting Laki fissure eruption of 1783-1784 was a part of the same fissure system. Grímsvötn was erupting at the same time as Laki during 1783, but continued to erupt until 1785. Because most of the volcano lies underneath Vatnajökull, most of its eruptions have been subglacial.

Jökulhlaup

Subglacial eruptions regularly give rise to glacial bursts, known in Icelandic as jökulhlaups. Eruptions may melt enough ice to fill the Grímsvötn caldera with water, and the pressure may be enough to suddenly lift the icecap, allowing huge quantities of water to escape rapidly. As a result, the Grímsvötn caldera is monitored very carefully by scientists. When a large eruption occurred in 1996, geologists knew well in advance that a glacial burst was imminent. It did not occur until several weeks after the eruption finished, but the monitoring let the Icelandic ring road (Hringvegur) be closed when the burst occurred. A section of road across the Skeiðará sandur was washed away in the ensuing flood, but no-one was hurt.

Last eruptions

A week-long eruption occurred at Grímsvötn starting on 28 December 1998, but no glacial burst occurred. In November 2004, another eruption of about one week began. Volcanic ash from the eruption fell as far away as mainland Europe and caused short-term disruption of airline traffic into Iceland, but again no glacial burst followed the eruption.

Bacteria in the lakes

In summer 2004 scientists found bacteria in the water of the Grímsvötn lakes under the glacier, the first time that subglacial lake–dwelling bacteria have been found [cite journal |quotes=no |url=http://www.nature.com/news/2004/040712/pf/040712-6_pf.html |journal=Nature |title=Glacial lake hides bacteria |author=Mark Peplow |date=2004-07-13 |doi=10.1038/news040712-6 |format=dead link|date=June 2008 – ^{[http://scholar.google.co.uk/scholar?hl=en&lr=&q=intitle%3AGlacial+lake+hides+bacteria&as_publication=%5B%5BNature+%28journal%29%7CNature%5D%5D&as_ylo=2004&as_yhi=2004&btnG=Search Scholar search]} ] . The lakes do not freeze totally because of the volcanic heat. The bacteria can also survive on a very low quantity of oxygen.

The scientists see a similarity to the planet Mars, because there are also traces of volcanism and glaciers on Mars. This could help identify where to look for life on Mars.

References

See also

* Geography of Iceland
* Glaciers of Iceland
* Glacial lake outburst flood
* Iceland plume
* Iceland hotspot
* Lakes of Iceland
* List of islands off Iceland
* List of volcanoes in Iceland
* Plate tectonics
* Rivers of Iceland
* Volcanoes of Iceland
* Waterfalls of Iceland

External links

*VNUM|1=1703-01=
* [http://volcano.und.edu/vwdocs/volc_images/img_grimsvotn.html Volcanism at Grímsvötn lakes]
* [http://www.lancs.ac.uk/ug/lloydca/formation.html Formation and emptying of glacier lakes]
* [http://news.bbc.co.uk/1/hi/sci/tech/3982273.stm BBC news report of the November 2004 eruption]
* [http://millhouse.nl/grimsvotn2004.html Photo report of the November 2004 eruption]
* [http://www.iol.co.za/index.php?set_id=14&click_id=420&art_id=qw1099460701116T614 Independent news report of the 2004 eruption]