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2010 eruptions of Eyjafjallajökull

From Wikipedia, the free encyclopedia

Coordinates: 63°37′59″N 19°36′00″W / 63.633°N 19.6°W / 63.633; -19.6

Volcano plume on 17April 2010.

Composite map of the volcanic ash cloud spanning 14–25April 2010

The 2010 eruptions of Eyjafjallajökull are a sequence of volcanic events at Eyjafjöll in Iceland which, although relatively small for volcanic eruptions, caused enormous disruption to air travel across western and northern Europe over an initial period of six days in April 2010. Additional localised disruption continued into May 2010.

Seismic activity started at the end of 2009 and gradually increased in intensity until on 20March 2010, a small eruption started that was rated as a 1 on the Volcanic Explosivity Index.[1]

Beginning on 14April 2010, the eruption entered a second phase and created an ash cloud that led to the closure of most of Europe's IFR airspace from 15 until 20April 2010. Consequently, a very high proportion of flights within, to, and from Europe were cancelled, creating the highest level of air travel disruption since the Second World War.

The second phase of the eruption started on 14April 2010 and resulted in an estimated 250 million cubic metres (330,000,000 cuyd) (¼km3) of ejected tephra. The ash plume rose to a height of approximately 9kilometres (30,000 ft), which rates the explosive power of the eruption as a 4 on the Volcanic Explosivity Index.[2]

By 21 May 2010, the second eruption phase had subsided to the point that no further lava or ash was being produced.

By the morning of 24 May 2010, the view from the web camera installed on Þórólfsfell showed only a plume of water vapour surrounded by a blueish haze caused by the emission of sulphurous gases.

Due to the large quantities of dry volcanic ash lying on the ground, surface winds frequently lifted up an "ash mist" that significantly reduced visibility and made web camera observation of the volcano impossible.[3]

By the evening of 6 June 2010, a small, new crater had opened up on the west side of the main crater from which explosive activity was observed with the emission of small quantities of ash.[4]

Seismic data showed that the frequency and intensity of earth tremors still exceeds the levels observed before the eruption, therefore scientists at the Icelandic Meteorological Office (IMO) and the Institute of Earth Sciences, University of Iceland (IES) continue to monitor the volcano closely.

Only when the activity of the volcano has ceased for three months will it then be regarded as being dormant.[5]

Background

Dust particles suspended in the atmosphere scatter light from the setting sun, generating 'volcanic lavenders' like this one over the flight path of Leeds-Bradford Airport in England during the aviation shutdown

Eyjafjallajökull (pronounced[ˈɛɪjaˌfjatl̥aˌjœkʏtl̥]( listen)) is one of the Iceland's smaller ice caps located in the far south of the island. It is situated to the north of Skógar and to the west of the larger ice cap Mýrdalsjökull.

The ice cap covers the caldera of a volcano 1,666metres (5,466 ft) in height that has erupted relatively frequently since the last ice age. The most recent major eruptions occurred in 920, 1612 (believed to have lasted only three days) and from 1821 to 1823 .[6] Previous eruptions of Eyjafjallajökull have been followed by eruptions at its larger neighbour, Katla;.[7] On 20April 2010 Icelandic President Ólafur Grímsson said that, "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".[8]

The volcanic events starting in March 2010 are considered to be a single eruption divided into different phases. The first eruption phase ejected olivine basaltic andesite lava[9] several hundred metres into the air in what is known as an effusive eruption. Ash ejection from this phase of the eruption is small, rising to no more than 4kilometres (2.5 mi) into the atmosphere.

On 14 April 2010, however, the eruption entered an explosive phase and ejected fine, glass-rich ash to over 8kilometres (5.0 mi) into the atmosphere. The second phase is estimated to be a VEI 4 eruption, which is large, but not nearly the most powerful eruption possible by volcanic standards. By way of comparison, the Mount St. Helens eruption of 1980 was rated as 5 on the VEI, and the 1991 eruption of Mount Pinatubo was rated as a 6.[citation needed]

What made this volcanic activity so disruptive to air travel was the combination of the following four factors:[citation needed]

1.  The volcano's location is directly under the Jet Stream

2.  The direction of the Jet Stream was unusually stable at the time of the eruption's second phase, maintaining a continuous south-easterly heading

3.  The second eruptive phase took place under 200m (660 ft) of glacial ice. The resulting meltwater flowed back into the erupting volcano which created two specific phenomena:

1.  The rapidly vapourising water significantly increased the eruption's explosive power

2.  The erupting lava cooled very rapidly, which created a cloud of highly abrasive, glass-rich ash

4.  The volcano's explosive power was sufficient to inject ash directly into the Jet Stream.

Without the specific combination of the above factors, the eruption of Eyjafjallajökull would have been a medium sized, somewhat non-descript eruption that would have been of little interest to those outside the scientific community or those living in the immediate vicinity.[citation needed] However, the above factors were precisely those required for the Jet Stream to carry the ash directly over Northern Europe into some of the busiest airspace in the world.

Public observations

People observing the first fissure at Fimmvörðuháls

"Volcano tourism" quickly sprang up in the wake of the eruption, with local tour companies offering day trips to see the volcano.[10]

However tourists should note that the Civil Protection Department of the Icelandic Police produce regular reports about access to the area, including an updated map of the Restricted Area around Eyjafjallajokull, from which the public is excluded.

Vodafone and the Icelandic telecommunications company Míla installed webcams giving views of the eruption from Valahnúkur, Hvolsvöllur and Þórólfsfell. The view of the eruption from Þórólfsfell also includes a thermal imaging camera.

Scientific observations

This eruption has been assigned the volcano number 1702-02 by the Global Volcanism Program.

The London Volcanic Ash Advisory Centre (VAAC), part of the UK Met Office, is responsible for forecasting the presence of volcanic ash in the north-east Atlantic. All ash dispersion models for this geographic region are produced by the VAAC in London.

A study by the Icelandic Meteorological Office published on December 2009 indicated an increase in seismic activity around the Eyjafjallajökull area during the years 2006–2009. The study reported increased activity that occurred between June and August 2009 (200events), compared to a total of about 250 earthquakes recorded between September 2006 and August 2009. It further indicated that the locations of most of the earthquakes in 2009 occurred between 8 to 12 kilometres (5.0 to 7.5 mi) depth east of the volcano‘s top crater.[11] At the end of December 2009, seismic activity began around the Eyjafjallajökull volcano area, with thousands of small earthquakes (mostly of magnitude 1–2Mw), 7 to 10 kilometres (4.3 to 6.2 mi) beneath the volcano.[12]

The radar stations of the Meteorological Institute of Iceland did not detect any appreciable amount of volcanic ashfall during the first 24hours of the eruption.[13] However, during the night of 22March, they reported some volcanic ash fall reaching the Fljótshlíð area (20 to 25 kilometres (12 to 16 mi) north-west of the eruption's location)[14] and Hvolsvöllur town (40kilometres (25 mi) north-west of the eruption location)[14] leaving vehicles with a fine grey layer of volcanic ash. At around 07:00 on 22March, an explosion launched eruption columns as far as 4kilometres (13,000 ft) straight up into the air. This was the highest plume since the eruption started.[15] On 23March, a small vapour explosion took place, when hot magma came into contact with nearby snowdrifts, emitting a huge vapour plume which reached an altitude of 7kilometres (23,000 ft), and was detected on radars from the Meteorological Institute of Iceland. Since then many vapour explosions have taken place.[16]

By 26February 2010 the Global Positioning System (GPS) equipment used by the Iceland Meteorological Office at Þorvaldseyri farm in the Eyjafjöll area (around 15kilometres (9.3 mi) southeast of the location of the recent eruption[14]) had shown 3centimetres of displacement of the local crust in a southward direction, of which a 1centimetre displacement had taken place within four days. (See the GPS Time Series page of the Nordic Volcanological Center's website for detailed information on the degree of movement detected in the Earth's crust in the Eyjafjallajökull locality.)

This unusual seismic activity along with the rapid movement of the Earth's crust in the area gave geophysicists evidence that magma was flowing from underneath the crust into the magma chamber of the Eyjafjallajökull volcano and that pressure stemming from the process caused (in geophysical terms) the huge crustal displacement at Þorvaldseyri farm.[17] The seismic activity continued to increase and from 3 to 5March, close to 3,000earthquakes were measured having their epicentre at the volcano. Most of these were too small (magnitude2) to be interpreted as precursors to an eruption, but some could be detected in nearby towns.[18]

The most up to date scientific observations are available at the website of the Institute of Earth Sciences which details the current's days events for the eruption in Eyjafjallajökull. The Nordic Volcanological Center also maintains an Eyjafjallajökull status page.

Phase 1: Effusive eruption

The first phase of the eruption lasted from 20March to 12April 2010 and was characterised by alkali-olivine basalt lava flowing from various eruptive vents on the flanks of the mountain.

Evacuations

About 500 farmers and their families from the areas of Fljótshlíð, Eyjafjöll, and Landeyjar were evacuated overnight (including a group of 30 schoolchildren and their 3 teachers [19][20] from Caistor Grammar School in England), and flights to and from Reykjavík and Keflavík International Airport were postponed, but on the evening of 21March, domestic and international air traffic was allowed again.[21][22][23] Inhabitants of the risk zone of Fljótshlíð, Eyjafjöll, and Landeyjar area were allowed to return to their farms and homes after an evening meeting with the Civil Protection Department on 22March and the evacuation plan was temporarily dismissed. Instead, the police closed the road to Þórsmörk, and the four-wheel-drive trail from Skógar village to the Fimmvörðuháls mountain pass, but these roads and trails were reopened on 29March, though only for suitable four-wheel drives. When the second fissure appeared, the road was closed again because of the danger of flash floods, which could have developed if the fissure had opened near big ice caps or other snow reservoirs, but the road was again opened at around noon on 1April.[24][25][26]

Effect on river water

On 22March, a flow meter device situated in the Krossá glacial river (which drains Eyjafjallajökull and Mýrdalsjökull glaciers) in the Þórsmörk area (a few kilometres north-west of the erupting location) started to record a sudden rise in water level and in water temperature – the total water temperature rose by 6°C (11°F) over a two-hour period, which had never occurred so quickly in the Krossá river since measurements began. Shortly afterward, the water level returned to normal and water temperature decreased as well.[27] It is thought that this rise in water temperature is related to the eruption nearby and is affecting part of the Krossá drainage basin. The temperature of Hruná river, which flows through the narrow Hrunárgil canyon, into which part of the lava stream has been flowing, was recently recorded by geologists to be between 50°C (122°F) and 60°C (140°F), indicating that the river has been cooling the lava in that canyon.[28]

Fissure

Second fissure, viewed from the north, on 2April 2010

The first phase of the 2010 eruption began late on the evening of 20March at the Eyjafjallajökull.

The initial visual report of the eruption was at 23:52GMT, when a red cloud was observed at the northern slopes of Fimmvörðuháls mountain pass,[29][30] lighting up the sky above the eruptive site. The eruption was preceded with intense seismicity and high rates of deformation in the weeks before the eruption, in association with magma recharging of the volcano. Immediately prior to the eruption the depth of seismicity had become shallow, but was not significantly enhanced from what it had been in the previous weeks. Deformation was occurring at rates of up to a centimetre a day since 4March at various GPS sites installed within 12kilometres (7.5 mi) from the eruptive site.[citation needed]

A fissure opened up about 150metres (490 ft) in length running in a north-east to south-west direction, with 10 to 12 erupting lava craters ejecting lava at a temperature of about 1,000°C (1,800°F) up to 150metres (490 ft) into the air. The lava is alkali olivine basalt [31] and is relatively viscous causing the motion of the lava stream to the west and east of the fissure to be slow. The molten lava has flowed more than 4,000metres (2.5 mi) to the north-east of the fissure and into Hrunagil canyon, forming a lava fall more than 200metres (660 ft) long and is slowly approaching Þórsmörk, but has not yet[update] reached the flood plains of Krossá.[32][33][34]

On 25March 2010, while studying the eruption, scientists witnessed, for the first time in history, the formation of a pseudocrater during a steam explosion.[35] Crustal expansion continued at Þorvaldseyri for two days after the eruption began, but has been slowly decreasing whilst the volcanic activity increased. This indicates that the rate at which magma is flowing into the magma chamber roughly equals the rate at which it is being lost due to the eruption, giving evidence that this phase of volcanic activity has reached equilibrium.[36]