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Grímsvötn

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Grímsvötn
Grímsvötn and the Vatnajökull glacier, Iceland, July 1972
Highest point
Elevation1,725 m (5,659 ft)[1]
ListingList of volcanoes in Iceland
Geography
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Geology
Mountain typevolcanic caldera
Last eruption22 May 2011

The Grímsvötn sub-glacial lakes (Icelandic pronunciation: ['krimsvœʰtn̥];[2] 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 / 64.417°N 17.333°W / 64.417; -17.333, 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 mi) high plumes accompanied by multiple earthquakes,[3][4][5][6] disrupting air travel in Iceland,[7][8] and in Greenland, Scotland, Norway, Ireland and England on 22–24 May. The eruption scale has been much larger than that of the 2010 eruption of Eyjafjallajökull.

Jökulhlaup

The caldera lake is covered by the Vatnajökull ice shelf which is about 200m (650 ft) thick, however only the southern section of the 6 x 8 km caldera is exposed. A geothermal area and subglacial eruptions in the caldera regularly causes glacial outbursts known as jökulhlaup.[9] 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[10] 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 and 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 tremors were recorded twice around Grímsvötn on 2 and 3 October 2010, possibly indicating an impending eruption.[11] 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

On 21 May 2011 at 19:25 UTC, an eruption began, with 12 km (7 mi) high plumes accompanied by multiple earthquakes.[4][5][6] The ash cloud from the eruption rose to 20 km (12 mi), and is so far 10 times larger than the 2004 eruption, and the strongest in Grímsvötn for 100 years.[12]

During 22 May the ash plume fell to around 10 km altitude, rising occasionally to 15 km.[13]

On 23 May, the eruption was releasing about 2000 tons of ash per second, totalling 120 million tons in the first 48 hours.[14] The 2011 eruption of Grímsvötn thus qualified as 4 (VEI4) on the Volcanic Explosivity Index (VEI), releasing more ash in the first 48 hours than Eyjafjallajökull released during its entire 2010 eruption.[15]

On 24 May poor weather prevented visual observation of the eruption plume, but it had an estimated height of below 5 km, implying that the eruption is significantly weaker than on previous days.[16]

Disruption to air travel

See also: Volcanic ash and air safety

Disruption to air travel in Iceland[17] commenced on 21 May, followed by Greenland, Scotland,[18] Norway (Svalbard)[19] and a small part of Denmark on subsequent days. On 24 May the disruption spread to Northern Ireland and to airports in northern England.[20]

By comparison, the 2010 disruption after the Eyjafjallajökull eruption was on a far wider scale.

Bacteria in the subglacial lakes

In summer 2004, a community of bacteria was detected in water of the Grímsvötn lake under the glacier, the first time that bacteria have been found in a subglacial lake. The lakes never freeze 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.[21]

See also

References

  1. ^ "Grímsvötn". Global Volcanism Program. Smithsonian Institution. Retrieved 2006-08-15.
  2. ^ "How to pronounce /grímsvötn/". youtube.com. Retrieved 2011-05-23.
  3. ^ Eldgos í Grímsvötnum
  4. ^ a b Njörður Helgason (2011-04-14). "Vegurinn um Skeiðarársand lokaður". mbl.is. Retrieved 2011-05-22.
  5. ^ a b "Iceland's most active volcano erupts - Europe". Al Jazeera English. 2011-05-21. Retrieved 2011-05-22.
  6. ^ a b "Iceland volcanic eruption 'not linked to the end of the world' | IceNews - Daily News". Icenews.is. Retrieved 2011-05-22.
  7. ^ Eurocontrol news statements
  8. ^ Iceland Volcano and Earthquake blog
  9. ^ [1] Jökulhlaup figure 8.1
  10. ^ Andrew J. RUSSELL, Andrew R. GREGORY, Andrew R.G. LARGE, P. Jay FLEISHER, Timothy D. HARRIS. Tunnel channel formation during the November 1996 jökulhlaup, Skeiðarárjökull, Iceland Annals of Glaciology, 2007, Volume 45, 95 - 103.
  11. ^ "Possible Harmonic tremor pulse at Grímsfjall volcano | Iceland Volcano and Earthquake blog". Jonfr.com. 2010-10-02. Retrieved 2011-05-22.
  12. ^ "Largest Volcanic Eruption in Grímsvötn in 100 Years". Daily News. Iceland Review Online. 2011-05-22. Retrieved 2011-05-22.
  13. ^ "Ash plume and lightning". Icelandic Met Office. 2011-05-22. Retrieved 2011-05-23.
  14. ^ http://www.ruv.is/frett/ekkert-akvedid-um-folksflutninga
  15. ^ http://www.jonfr.com/volcano/?p=969#comments
  16. ^ "Update on volcanic activity in Grímsvötn". Icelandic Met Office. 2011-05-24. Retrieved 2011-05-24.
  17. ^ Eurocontrol news
  18. ^ Scottish flights grounded by Iceland volcanic ash cloud
  19. ^ Iceland eruption hits Norwegian flights
  20. ^ Eurocontrol news
  21. ^ Gaidos, E., et al. A Viable Microbial Community in a Subglacial Volcanic Crater Lake, Iceland. Astrobiology, 2004, Volume 4, Number 3, 327- 344, reported by Peplow, Mark (2004-07-13). "Glacial lake hides bacteria". Nature. doi:10.1038/news040712-6.

External links

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