Eyjafjallajökull

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

Eyjafjallajökull ([pronunciation?], translated as "island-mountains glacier") (listenⓘ) is one of the smaller glaciers of Iceland, situated to the north of Skógar and to the west of Mýrdalsjökull. The icecap of the glacier covers a volcano with a summit elevation of 1,666 metres (5,466 ft). The volcano has erupted relatively frequently since the Ice Age.[1]

The glacier covers an area of about 100 square kilometres (39 sq mi). The south end of the mountain was once part of the island's Atlantic coastline, but the sea has since retreated some 5 kilometres (3.1 mi), with the former coastline now forming sheer cliffs with a multitude of beautiful 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 volcano, which has a crater 3–4 kilometres (1.9–2.5 mi) in diameter, erupted in 920, 1612 and again from 1821 to 1823 when it caused a fatal glacial lake outburst flood.[2]Most recently it erupted twice in 2010 - on 20 March and 14 April. The March event forced a brief evacuation of around 500 local people[3][4], but the April eruption was ten to twenty times more powerful and caused massive disruption to air traffic across Northern Europe.

Etymology

The name usually describes the small mountains which form the foot of the volcano. The village and museum of Skógar are also part of the region "undir Eyjafjöllum" (under the Eyjafjall mountains).

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.[5] However, fissure vents occur on both (mainly the west) sides of the volcano. [6]

1821 eruption

This event was a rather small eruption,[7] yet some damage was caused. This was especially because the ash contained a large fraction of fluoride, which in high doses may have a negative influence on 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 eruption continued on a more subdued level until June 1822.

From the end of June till the beginning of August 1822, another series 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 the spring of 1823, the nearby volcano Katla under the glacier Mýrdalsjökull 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 68-70% SiO2.

2010 eruptions

Main article: 2010 eruptions of Eyjafjallajökull
A
A photo of Eyjafjallajökull taken from Route 1 in August 2009.

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.[8] On 26 February 2010, unusual seismic activity along with rapid expansion of the Earth's crust was registered by the Meteorological Institute of Iceland.[9] 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.[10] The seismic activity continued to increase and from March 3-5, close to 3,000 earthquakes were measured at the epicentre of the volcano.

The eruption on 27 March 2010

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.[11] This eruption was explosive in nature and is estimated to be ten to twenty times larger than the previous one in Fimmvörðuháls. This second eruption threw volcanic ash several kilometres up in the atmosphere which led to air travel disruptions in northwest Europe starting on April 15th 2010, including the closure of airspace over most of Europe.[12][13]

Eyjafjallajökull and Katla

Eyjafjallajökull in March 2006, viewed from a recreation area on the Sólheimajökull, a glacier on the Katla volcano

Over the past 1,100 years, Eyjafjallajökull has erupted four times: in 920, 1612, between 1821–1823, and in 2010. Each of the first three of these incidents preceded an eruption in the nearby subglacial volcano, Katla.[14] Katla – a much more active volcano known for its powerful subglacial eruptions and its large magma chamber, much larger than that of the Eyjafjallajökull volcano system – has not shown any unusual activity, such as expansion of the crust or seismic activity, in 2010. Some geophysicists in Iceland support the notion that the recent volcanic eruption at Eyjafjallajökull may trigger a second eruption at Katla, one which would cause major flooding due to melting of glacial ice.[15][16]

North view of Eyjafjallajökull on April 4 2010, taken from an altitude of 10,000 meters

See also

References

  1. ^ "Increasing signs of activity at Eyjafjallajökull in Iceland : Eruptions". Scienceblogs.com. doi:10.1016/j.jog.2006.09.005. Retrieved 2010-04-17.
  2. ^ "Last Eyjafjallajökull Eruption Lasted Two Years", Iceland Review
  3. ^ "Iceland's hottest ticket - volcano tourism", The Guardian
  4. ^ "Volcano erupts in Iceland" Hundreds of people evacuated from areas near glacier but no immediate reports of damage or injuries, The Guardian
  5. ^ "Eyjafjallajökull: Eruptive History". Global Volcanism Program. Smithsonian Institution. Retrieved 2010-4-18. {{cite web}}: Check date values in: |accessdate= (help)
  6. ^ "Eyjafjallajökull: Summary". Global Volcanism Program. Smithsonian Institution. Retrieved 2010-4-18. {{cite web}}: Check date values in: |accessdate= (help)
  7. ^ 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. [1] (PDF)
  8. ^ Veðurstofa Íslands (5 March 2010) "Jarðskjálftahrina undir Eyjafjallajökli". Veðurstofa Ísland (The Meteorological Institute of Iceland).
  9. ^ "Fasteignaskrá measurement tools".
  10. ^ Morgublaðið (26.02.2010) "Innskot undir Eyjafjallajökli". Morgunblaðið.
  11. ^ "Iceland's volcanic ash halts flights in northern Europe". BBC News. 15 April 2010. Retrieved 15 April 2010.
  12. ^ ""Icelandic volcanic ash alert grounds UK flights"". BBCNews. Retrieved 15 April 2010.
  13. ^ « Island volcano awakened - volcano with glaciers Eyjafjallajökull », peoplestar.co.uk, 2010-04-16.
  14. ^ Roger Boyes. ""Iceland prepares for second, more devastating volcanic eruption"". TimesOnline. Retrieved 21 March 2010.
  15. ^ Boyes, Roger (21 March 2010). "Iceland prepares for second, more devastating volcanic eruption". Times Online. Retrieved 22 March 2010.
  16. ^ Kastljósið 22.3.2010, Sjónvarpið, "Viðtal við Dr. Pál Einarsson, jarðeðlisfræðing"

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