Grímsvötn

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Grímsvötn
Ash from Grímsvötn volcano across Vatnajökull ice cap, November 7, 2004
Elevation	1,725 m (5,659 ft)
Location	Austur-Skaftafellssýsla / Vestur-Skaftafellssýsla, Iceland
Coordinates	64.42° N 17.33° W
Type	volcanic caldera
Last eruption	2004

The Grímsvötn (Icelandic vatn, or "lake") are lakes in Iceland. They lie in the highlands of Iceland at the northwestern side of the Vatnajökull glacier and are covered by its ice cap. Beneath them is a large magma chamber of a powerful volcano. The location of the lakes is 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 Laki fissure eruption of 1783-1784 was a part of the same fissure system. In fact, 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 eruptions have been subglacial in nature.

1 Jökulhlaup
2 Last eruptions
3 Bacteria in the lakes
4 References
5 See also
6 External links

[edit] Jökulhlaup

Eruptions under the icecap 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 didn't occur until several weeks after the eruption finished, but the monitoring allowed the closing of the Icelandic ring road (Hringvegur) when the burst occurred. A section of road across the Skeiðará sandur was washed away in the ensuing flood, but no-one was hurt.

[edit] Last eruptions

Ash plume from Grímsvötn Volcano, November 2, 2004

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 run followed the eruption.

[edit] Bacteria in the lakes

In summer 2004 scientists found bacteria in the water of the Grímsvötn lakes under the glacier, the first time subglacial lake–dwelling bacteria have been found ^[1]. The lakes do not freeze totally because of the volcanic heat. The bacteria are also able to 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.