Grímsvötn

Grímsvötn
Grímsvötn and the Vatnajökull glacier, Iceland, July 1972
Highest point
Elevation	1,725 m (5,659 ft)
Listing	List of volcanoes in Iceland
Geography
Grímsvötn Austur-Skaftafellssýsla / Vestur-Skaftafellssýsla, Iceland
Geology
Mountain type	volcanic caldera
Last eruption	22 May 2011

The Grímsvötn sub-glacial lakes (Icelandic pronunciation: ['kriːmsvœʰtn̥]; vötn = "waters", singular: [vatn] Error: {{Lang}}: text has italic markup (help)) and the volcano of the same name are in South-East Iceland. They are in the highlands of Iceland at the northwestern side of the Vatnajökull ice-cap. The lakes are at 64°25′N 17°20′W, at an elevation of 1,725 m (5,659 ft). Beneath the lakes is the magma chamber of the Grímsvötn volcano.

Grímsvötn is a basaltic volcano which has the highest eruption frequency of all the volcanoes in Iceland and has a southwest-northeast-trending fissure system. 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 and the interaction of magma and meltwater from the ice causes phreatomagmatic explosive activity.

On 21 May 2011 at 19:25 UTC, an eruption began, with 12 km (7.5 mi) high plumes accompanied by multiple earthquakes, disrupting air travel in Iceland, and in Greenland, Scotland and Norway on 22-23 May. The eruption scale has been much larger than that of the 2010 eruption of Eyjafjallajokull .

Jökulhlaups

See also: Jökulhlaup

Subglacial eruptions regularly give rise to glacial bursts 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. Consequently, the Grímsvötn caldera is monitored very carefully. 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 monitoring ensured that the Icelandic ring road (Hringvegur) was 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.

1998 & 2004 eruptions

A week-long eruption occurred at Grímsvötn starting on 28 December 1998, but no glacial burst occurred. In November 2004, a week-long eruption occurred. 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.

2010 glacial flood

Harmonic tremor were recorded twice around Grímsvötn on 2 and 3 October 2010, possibly indicating an impending eruption. At the same time, sudden inflation was measured by GPS in the volcano, indicating magma movement under the mountain. On 1 November 2010 meltwater from the Vatnajökull glacier was flowing into the lake, suggesting that an eruption of the underlying volcano might be imminent.

2011 eruption

Harmonic tremors were recorded twice around Grímsvötn on 2 and 3 October 2010, possibly indicating an impending eruption. At the same time, sudden inflation was measured by GPS in the volcano, indicating magma movement under the mountain. On 1 November 2010 meltwater from the Vatnajökull glacier was flowing into the lake, suggesting that an eruption of the underlying volcano might be imminent.

On 21 May 2011 at 19:25 UTC, an eruption began, with 12 km (7.5 mi) high plumes accompanied by multiple earthquakes. The ash cloud from the eruption rose to 20km/12 miles, and is so far 10 times larger than the 2004 eruption, and the strongest in Grímsvötn for 100 years.

During 22 May the ash plume fell to around 10 km altitude, rising occasionally to 15 km.

As of writing, the eruption has been releasing about 2000 tons of ash per second, making it 120 million tons in the first 48 hours . This makes the 2011 eruption of Grimsvotn a confortable VEI4 in the scale of volcanic explosive index (VEI), releasing more ash in the first 48 hours than Eyjafjallajokull during its entire 2010 eruption .

Disruption to Air Travel

Disruption air travel in Iceland commenced on 21 May, followed by Greenland, Scotland and Norway (Svalbard) on subsequent days.

Bacteria in the subglacial lakes

In summer 2004, bacteria were detected in the water of the Grímsvötn lakes under the glacier, the first time that bacteria were found in a subglacial lake. The lakes do not freeze totally because of the volcanic heat. The bacteria can also survive at low concentrations of oxygen. The site is a possible analogue for life on the planet Mars, because there are also traces of volcanism and glaciers on Mars and thus the findings could help identify how to look for life on Mars.

See also

• Volcanism in Iceland
• List of volcanoes in Iceland
• Geography of Iceland
• Glaciers of Iceland
• Glacial lake outburst flood
• Iceland plume
• Iceland hotspot
• Lakes of Iceland
• List of islands of Iceland
• Timetable of major worldwide volcanic eruptions
• Plate tectonics

External links

• Update on Grímsvötn Activity - from the Icelandic Met Office and University of Iceland (updated at least daily)
• Current seismology around Grímsvötn – Earthquakes in last 48 hours
• Grímsvötn statement from Eurocontrol European Air Traffic Control (updated frequently)
• Grímsvötn volcanic ash advisory from regional Volcanic Ash Advisory Centre, London (updated every 6 hours)
• Grímsvötn updates from NATS - UK air traffic control plus the Eastern part of the North Atlantic
• Live air traffic and ash cloud position
• BBC news report of the 23 May 2011 eruption
• Report on the start of the Grímsvötn eruption from the Icelandic Met Office
• "Grímsvötn". Global Volcanism Program. Smithsonian Institution.
• Formation and emptying of glacier lakes
• Photo report of the November 2004 eruption
• Independent news report of the 2004 eruption
• Grimsvötn eruption – frequently asked questions