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Eyjafjallajökull

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Map showing the location of
Map showing the location of
Location in Iceland
LocationIceland
Area100 km2 (40 sq mi)
Thickness28018

Eyjafjallajökull ([pronunciation?], listenⓘ)—Icelandic for "island-mountain glacier"[1]—is one of the smaller ice caps of Iceland, situated to the north of Skógar and to the west of Mýrdalsjökull. The ice cap covers the caldera of the volcano with a summit elevation of 1,666 metres (5,466 ft) . The volcano has erupted relatively frequently since the last glacial period, most recently from 1821 to 1823 and again in 2010.[2][3][4]

Geography

The ice cap covers an area of about 100 square kilometres (39 sq mi), feeding many outlet glaciers. The main outlet glaciers are to the north; Gígjökull, flowing into Lónið, and Steinholtsjökull, flowing into Steinholtslón.

The mountain, a stratovolcano, stands 1,651 metres (5,417 ft) at it highest point, and has a crater 3–4 kilometres (1.9–2.5 mi) in diameter, open to the north. The crater rim has three main peaks, being (clockwise from the north-east) Guðnasteinn, 1,500 metres (4,900 ft) (approx), Hámundur, 1,651 metres (5,417 ft) and Goðasteinn, 1,497 metres (4,911 ft). The south face of the mountain was once part of Iceland's Atlantic coastline, from which, over thousands of years, the sea has retreated some 5 kilometres (3.1 mi). The former coastline now consists of sheer cliffs with many waterfalls, of which the best known is Skógafoss. In strong winds, the water of the smaller falls can even be blown up the mountain. The area between the mountain and the present coast is a relatively flat strand, 2 to 5 km wide, (misleadingly) called the Eyjafjöll.

The volcano is fed by a magma chamber under the mountain, which in turn derives from the tectonic divergence of the Mid-Atlantic Ridge. It is part of a chain of volcanoes stretching across Iceland. Its nearest active neighbours are Katla, to the northeast, and Eldfell, on Heimaey, to the southwest. The volcano is thought to be related to Katla geologically, in that eruptions of Eyjafjallajökull have generally been followed by eruptions of Katla. The Eyjafjallajökull volcano erupted in 920, 1612 and again from 1821 to 1823 when it caused a glacial lake outburst flood or jökulhlaup.[5] It has erupted twice in 2010—on 20 March and in April/May. The March event forced a brief evacuation of around 500 local people,[6][7] but the 14 April eruption was ten to twenty times more powerful and caused substantial disruption to air traffic across Europe, and is ongoing. It has cancelled thousands of flights across and to Iceland.

Etymology

Active volcanic areas and systems in Iceland

The name Eyjafjallajökull is made up of the words eyja (genitive plural of ey, meaning eyot or island), fjalla (genitive plural of fjall, whose nominative plural is fjöll, meaning fells or mountains) and jökull (meaning glacier, cognate with the -icle in icicle). A literal translation would thus be the "island-fells glacier" or the "island-mountains glacier". The name Eyjafjöll describes the southern side of the volcanic massif together with the small mountains which form the foot of the volcano. The village and museum of Skógar are also part of the region undir Eyjafjöllum (meaning "under the Eyjafjalls").

Geology

The stratovolcano, whose vents follow an east-west trend, is composed of basalt to andesite lavas. Most of its historical eruptions have been explosive.[8] However, fissure vents occur on both (mainly the west) sides of the volcano.[9]

1821 to 1823 eruptions

Some damage was caused by a minor eruption in 1821.[10] Notably, the ash released from the eruption contained a large fraction of fluoride, which in high doses may harm the bone structure of cattle, horses, sheep and humans. The eruption also caused some small and medium glacier runs and flooding in nearby rivers Markarfljót and Holtsá. The eruptive phase started on 19 and 20 December 1821 by a series of explosive eruptions and continued over the next several days. The sources describe heavy ash fall in the area around the volcano, especially to the south and west.

After that event the sequence of eruptions continued on a more subdued level until June 1822.

From the end of June until the beginning of August 1822, another sequence of explosive eruptions followed. The eruption columns were shot to considerable heights, with ashfall in both the far north of the country, in Eyjafjörður, and in the southwest, on the peninsula of Seltjarnarnes near Reykjavík.

The period from August to December 1822 seemed quieter, but farmers attributed the death of cattle and sheep in the Eyjafjörður area to poisoning from this eruption, which modern analysis identifies as fluoride poisoning. Some small glacier runs occurred in the river Holtsá. A bigger one flooded the plains near the river Markarfljót. The sources don’t indicate the exact date.

In 1823, some men went hiking up on Eyjafjallajökull to inspect the craters. They discovered a fissure vent near the summit caldera a bit to the west of Guðnasteinn.

In early 1823, the nearby volcano Katla under the Mýrdalsjökull ice cap erupted and at the same time steam columns were seen on the summit of Eyjafjallajökull.

The ash of Eyjafjallajökull’s 1821 eruptions is to be found all over the south of Iceland. It is dark grey in colour, small-grained and intermediate rock containing about 28-40% silicon dioxide.

2010 eruptions

Main articles: 2010 eruptions of Eyjafjallajökull, Aftermath of the 2010 Eyjafjallajökull eruption, and Air travel disruption after the 2010 Eyjafjallajökull eruption
A
A photo of Eyjafjallajökull taken from Route 1 in August 2009
The eruption on 27 March 2010

Around December 2009, seismic activity was detected in the volcano area, with thousands of small earthquakes (mostly magnitude 1–2 on the Richter magnitude scale, with only a couple greater than 3 magnitude) 7–10 kilometres (4.3–6.2 mi) beneath the volcano.[11] On 26 February 2010, unusual seismic activity along with rapid expansion of the Earth's crust was registered by the Meteorological Institute of Iceland.[12] This gave geophysicists evidence that magma was pouring from underneath the crust into the magma chamber of the Eyjafjallajökull volcano and that pressure stemming from the process caused the huge crustal displacement at Þorvaldseyri farm.[13] The seismic activity continued to increase and from 3–5 March, close to 3,000 earthquakes were measured at the epicentre of the volcano.

The eruption is thought to have begun on 20 March 2010, about 8 kilometres (5.0 mi) east of the top crater of the volcano in a popular hiking region called Fimmvörðuháls. This first eruption, in the form of a fissure vent, did not occur under the glacier and was smaller in scale than had been thought by some geologists.

On 14 April 2010 Eyjafjallajökull resumed erupting after a brief pause, this time from the top crater in the centre of the glacier, causing meltwater floods (also known as jökulhlaup) to rush down the nearby rivers, and requiring 800 people to be evacuated.[4] This eruption was explosive in nature, due to melt water getting into the glacier. It is estimated to be ten to twenty times larger than the previous one in Fimmvörðuháls. This second eruption, which is ongoing, threw volcanic ash several kilometres up in the atmosphere which led to air travel disruption in northwest Europe for six days from 15 April and in May 2010, including the closure of airspace over many parts of Europe. [14] The eruptions also created electrical storms.[15]. On 23rd May 2010, the London Volcanic Ash Advisory Commission declared the eruption to have stopped, but are continuing to monitor the volcano[16].

Eyjafjallajökull and Katla

Eyjafjallajökull in March 2006, viewed from a recreation area on the Sólheimajökull, a glacier on the Katla volcano
North view of (from left to right) Mýrdalsjökull, Fimmvörðuháls and Eyjafjallajökull on 4 April 2010, taken from an altitude of 10,000 metres (32,800 ft)

Eyjafjallajökull lies 25 km[17] west of another subglacial volcano, Katla, under the Mýrdalsjökull ice cap, which is much more active and known for its powerful subglacial eruptions and its large magma chamber. Each of the eruptions of Eyjafjallajökull in 920, 1612, and 1821-1823 has preceded an eruption of Katla.[18] Katla has not displayed any unusual activity (such as expansion of the crust or seismic activity) during the 2010 eruptions of Eyjafjallajökull, though geologists have been concerned about the general instability of the larger volcano since 1999. Some geophysicists in Iceland believe that the Eyjafjallajökull eruption may trigger an eruption of Katla, which would cause major flooding due to melting of glacial ice and send up massive plumes of ash.[18][19] On 20 April 2010 Icelandic President Ólafur Grímsson said "the time for Katla to erupt is coming close...we [Iceland] have prepared...it is high time for European governments and airline authorities all over the world to start planning for the eventual Katla eruption".[20]

See also

References

  1. ^ "A guide to Iceland's volcanoes". BBC News. 15 April 2010. Retrieved 20 April 2010.
  2. ^ "Increasing signs of activity at Eyjafjallajökull in Iceland : Eruptions". Scienceblogs.com. doi:10.1016/j.jog.2006.09.005. Retrieved 2010-04-17.
  3. ^ The 1821-1823 erruptins come from Larsen, G., 1999. Gosið í Eyjafjallajökli 1821–1823 (The eruption of the Eyjafjallajökull volcano in 1821–1823). Science Institute Research Report RH-28-99. 13 p. Reykjavík. [1] (PDF)
  4. ^ a b "Iceland's volcanic ash halts flights in northern Europe". BBC News. 15 April 2010. Retrieved 15 April 2010.
  5. ^ ""Last Eyjafjallajökull Eruption Lasted Two Years", Iceland Review". Icelandreview.com. Retrieved 2010-04-18.
  6. ^ ""Iceland's hottest ticket — volcano tourism", The". Guardian. Retrieved 2010-04-18.
  7. ^ Associated Press (2010-03-25). ""Volcano erupts in Iceland" Hundreds of people evacuated from areas near glacier but no immediate reports of damage or injuries, The". Guardian. Retrieved 2010-04-18.
  8. ^ "Eyjafjallajökull: Eruptive History". Global Volcanism Program. Smithsonian Institution. Retrieved 2010-04-18.
  9. ^ "Eyjafjallajökull: Summary". Global Volcanism Program. Smithsonian Institution. Retrieved 2010-04-18.
  10. ^ The following description is an abstract of Larsen, G., 1999. Gosið í Eyjafjallajökli 1821–1823 (The eruption of the Eyjafjallajökull volcano in 1821–1823). Science Institute Research Report RH-28-99. 13 p. Reykjavík. [2] (PDF)
  11. ^ Veðurstofa Íslands (5 March 2010) "Jarðskjálftahrina undir Eyjafjallajökli". Veðurstofa Ísland (The Meteorological Institute of Iceland).
  12. ^ "Fasteignaskrá measurement tools".
  13. ^ Morgublaðið (26.02.2010) "Innskot undir Eyjafjallajökli". Morgunblaðið.
  14. ^ BBC: Row grows over airspace shutdown costs, 22 April 2010
  15. ^ "'Dirty thunderstorm': Lightning in a volcano".
  16. ^ http://www.metoffice.gov.uk/aviation/vaac/vaacuk.html. {{cite web}}: Missing or empty |title= (help)
  17. ^ "Green.view: Back into the clouds". The Economist. 2010-04-16. Retrieved 2010-04-22.
  18. ^ a b Roger Boyes. ""Iceland prepares for second, more devastating volcanic eruption"". TimesOnline. Retrieved 21 March 2010.
  19. ^ Kastljósið 22.3.2010, Sjónvarpið, "Viðtal við Dr. Pál Einarsson, jarðeðlisfræðing"
  20. ^ BBC Newsnight interview with President Grímsson of Iceland, 20 April 2010
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