2010 eruptions of Eyjafjallajökull

Between March and June 2010 a series of volcanic events at Eyjafjallajökull in Iceland caused enormous disruption to air travel across Western Europe.

The disruptions started over an initial period of six days in April 2010. Additional localised disruption continued into May 2010, and eruptive activity persisted until June 2010. The eruption was declared officially over in October 2010, after 3 months of inactivity, when snow on the glacier did not melt. From 14 to 20 April, ash from the volcanic eruption covered large areas of Northern Europe. About 20 countries closed their airspace to commercial jet traffic and it affected approximately 10 million travellers.

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

Beginning on 14 April 2010, the eruption entered a second phase and created an ash cloud that led to the closure of most of the European IFR airspace from 15 until 20 April 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 resulted in an estimated of ejected tephra and an ash plume that rose to a height of around , which rates the explosive power of the eruption as a 4 on the Volcanic Explosivity Index.Erica R. Hendry
What We Know From the Icelandic Volcano
," '' Smithsonian'', 22 April 2010. Retrieved April 2010. By 21 May 2010, the second eruption phase had subsided to the point that no further lava or ash was being produced.

By the evening of 6 June 2010, a small, new crater had opened up on the west side of the main crater. Explosive activity from this new crater was observed with emission of small quantities of ash. Seismic data showed that the frequency and intensity of earth tremors still exceeded the levels observed before the eruption, therefore scientists at the Icelandic Meteorological Office (IMO) and the Institute of Earth Sciences, University of Iceland (IES) continued to monitor the volcano.

In October 2010, Ármann Höskuldsson, a scientist at the University of Iceland Institute of Earth Sciences, stated that the eruption was officially over, although the area was still geothermally active and might erupt again.

Background

Eyjafjallajökull () is one of Iceland's smaller ice caps located in the far south of the island. Situated to the north of Skógar and to the west of the larger ice cap Mýrdalsjökull, Eyjafjallajökull covers the caldera of a volcano high, which has erupted relatively frequently since the last ice age. The most recent major eruptions occurred in 920, 1612, and from 1821 to 1823. Previous eruptions of Eyjafjallajökull have been followed by eruptions at its larger neighbour, Katla. On 20 April 2010 Icelandic President Ólafur Grímsson said, "the time for Katla to erupt is coming close ... we celandhave prepared ... it is high time for European governments and airline authorities all over the world to start planning for the eventual Katla eruption."

The volcanic events starting in March 2010 were considered to be a single eruption divided into phases. The first eruption phase ejected olivine basaltic andesite lava several hundred metres into the air in what is known as an effusive eruption. Ash ejection from this phase of the eruption was small, rising to no more than into the atmosphere.

On 14 April 2010, however, the eruption entered an explosive phase and ejected fine glass-rich ash to over into the atmosphere. The second phase was estimated to be a VEI 4 eruption, which was 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. This second phase erupted trachyandesite.

This volcanic activity so disruptive to air travel because of a combination of factors:
# The volcano is directly under the jet stream.
# The direction of the jet stream was unusually stable at the time of the eruption's second phase, continuously southeast.
# The second eruptive phase happened under of glacial ice. The resulting meltwater flowed back into the erupting volcano, which created two specific phenomena:
## The rapidly vaporising water significantly increased the eruption's explosive power.
## The erupting lava cooled very fast, which created a cloud of highly abrasive, glass-rich ash.
# The volcano's explosive power was enough to inject ash directly into the jet stream.

Public observations

"Volcano tourism" quickly sprang up in the wake of the eruption, with local tour companies offering day trips to see the volcano. The Civil Protection Department of the Icelandic Police produced regular reports about access to the area, including a map of the restricted area around Eyjafjallajokull, from which the public was forbidden. Teams from the Icelandic Association for Search and Rescue were stationed at the eruption site as part of standard safety measures and to assist in enforcing access restrictions.

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 Þórólfsfel also includes a thermal imaging camera.

Scientific observations

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

A study by the Icelandic Meteorological Office published in 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 (200 events), 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 depth east of the volcano's top crater. At the end of December 2009, seismic activity began around the Eyjafjallajökull volcano area, with thousands of small earthquakes (mostly of magnitude 1–2  M_w), beneath the volcano.

The radar stations of the Meteorological Institute of Iceland did not detect any appreciable amount of volcanic ashfall during the first 24 hours of the eruption. However, during the night of 22 March, they reported some volcanic ash fall reaching the Fljótshlíð area ( northwest of the eruption's location) and Hvolsvöllur town ( northwest of the eruption location) leaving vehicles with a fine, grey layer of volcanic ash. At around 07:00 on 22 March, an explosion launched eruption columns as far as straight up into the air. This was the highest plume since the eruption started. On 23 March, a small vapour explosion took place, when hot magma came into contact with nearby snowdrifts, emitting a vapour plume which reached an altitude of , and was detected on radar from the Meteorological Institute of Iceland. After that, many further vapour explosions occurred.

By 26 February 2010, the global positioning system (GPS) equipment used by the Iceland Meteorological Office at Þorvaldseyri farm in the Eyjafjöll area (around southeast of the location of the recent eruption)Measurements made by using maps and measurement tools from Fasteignaskrá Íslandskort had shown 3 cm of displacement of the local crust in a southward direction, of which a 1-cm displacement had taken place within four days.

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 Eyjafjallajökull's magma chamber and that pressure stemming from the process caused the crustal displacement at Þorvaldseyri farm. The seismic activity continued to increase, and from 3 to 5 March, close to 3,000 earthquakes were measured having their epicentre at the volcano. Most of these were too small (magnitude 2) to be interpreted as precursors to an eruption, but some could be detected in nearby towns.

The grounding of European flights avoided about 3.44 kg of CO₂ emissions per day, while the volcano emitted about 1.5 kg of CO₂ per day.

Phase 1: Effusive eruption

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

Evacuations

About 500 farmers and their families had to escape from the areas of Fljótshlíð, Eyjafjöll, and Landeyjar were evacuated overnight (including a group of 30 schoolchildren and their three teachers from Caistor Grammar School in England), and flights to and from Reykjavík and Keflavík International Airport were postponed, but on the evening of 21 March, domestic and international air traffic was allowed again. 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 22 March 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 29 March, though only for suitable four-wheel drive vehicles. 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 1 April.

Effects on the river

On 22 March, a flow meter device 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 water temperature – the total water temperature rose by over a two-hour period, which had never happened so quickly in the Krossá river since measurements began. Shortly afterward, the water level returned to normal and water temperature decreased. This rise in water temperature was thought to be related to the eruption nearby and was 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 was flowing, was recently recorded by geologists to be between , indicating that the river was cooling the lava in that canyon.

Fissure

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

The initial visual report of the eruption was at 23:52 GMT, when a red cloud was seen at the north slopes of Fimmvörðuháls mountain pass, lighting up the sky above the eruptive site. The eruption was preceded by intense seismicity and high rates of deformation in the weeks before the eruption, in association with magma recharging of the volcano. Immediately before the eruption, the depth of the seismicity had become shallow, but was not significantly enhanced from what it had been in the previous weeks. Deformation was occurring at rates up to a centimetre a day since 4 March at various GPS sites installed within from the eruptive site.

A fissure opened up about in length running in a north-east to south-west direction, with 10 to 12 erupting lava craters ejecting lava at a temperature around up to into the air. The lava was alkali olivine basalt and was relatively viscous, causing the motion of the lava stream to the west and east of the fissure to be slow. The molten lava flowed more than to the north-east of the fissure and into Hrunagil canyon, forming a lava fall more than long and slowly approaching Þórsmörk, but had not reached the flood plains of Krossá.

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

A new fissure opened on 31 March, around northwest of the original fissure. Many witnesses were present while the new fissure opened. It was a bit smaller, around long according to witnesses, and lava coming from it started to flow into Hvannárgil canyon. These two erupting fissures shared the same magma chamber, according to geophysicists. No unusual seismic activity was detected at the time the new fissure appeared, nor any crustal expansion according to many seismometers and GPS recorders situated in nearby areas.

Geophysicist Magnús Tumi Einarsson said (at a press meeting in Hvolsvöllur on 21 March) that this eruption was small compared to, for example, the eruption of Hekla in 2000. The eruption, rather than taking place under the ice cap of the glacier, occurred in the mountain pass between the Eyjafjallajökull and Mýrdalsjökull glaciers. As long as the fissure was not near the glacier, the risk of flooding was minimal; however, the fissure could extend into the ice cap, thereby greatly increasing the risk of flooding.

Phase 2: Explosive eruption

After a short hiatus in eruptive activity, and a large increase in seismic activity 23:00 on 13 April and 1:00 on 14 April, a new set of craters opened early in the morning of 14 April 2010 under the volcano's ice-covered central summit caldera. The earthquake swarm was followed by the onset of a seismic eruption tremor. Meltwater started to emanate from the ice cap around 07:00 on 14 April and an eruption plume was observed in the early morning. Visual observations were greatly restricted due to cloud cover over the volcano, but an aeroplane of the Icelandic Coast Guard imaged eruptive craters with radar instruments. A series of vents along a two-kilometre-long north–south-oriented fissure was active, with meltwater flowing mostly down the northern slopes of the volcano, but also to the south. An ash-loaded eruption plume rose to more than , deflected to the east by westerly winds.

Ash analysis

Samples of volcanic ash collected near the eruption showed a silica concentration of 58%—much higher than in the lava flows. The concentration of water-soluble fluoride was one-third of the concentration typical in Hekla eruptions, with a mean value of 104 mg of fluoride per kg of ash. Agriculture is important in this region of Iceland, and farmers near the volcano have been warned not to let their livestock drink from contaminated streams and water sources, as high concentrations of fluoride can have deadly renal and hepatic effects, particularly in sheep.

Impact on farming

The Icelandic Food and Veterinary Authority released an announcement on 18 April 2010, asking that all horse owners who keep their herds outside be on the alert for ash fall. Where ash fall was significant, all horses had to be sheltered indoors. The thick layer of ash that had fallen on some Icelandic pastures and farms at Raufarfell had become wet and compact, making it very difficult to continue farming, harvesting, or grazing livestock.

Timeline of the second eruption phase

Unlike the earlier eruption phase, the second phase occurred beneath glacial ice. Cold water from melted ice quickly chilled the lava, causing it to fragment into highly abrasive glass particles that were then carried into the eruption plume. This, together with the magnitude of the eruption (estimated to be VEI 4) and being 10 to 20 times larger than the eruption of Fimmvörðuháls on 20 March, injected a glass-rich ash plume into the jet stream.

In addition to volcanic ash being very hazardous to aircraft, the location of this eruption directly under the jet stream ensured that the ash was carried into the heavily used airspace over northern and central Europe.

Phase 3: Return to dormancy

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 bluish haze caused by 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.

On 21 June 2010, data from seismic recorders in the area indicated that the frequency and strength of earth tremors had diminished, but were continuing.

In October 2010, Ármann Höskuldsson, a scientist at the University of Iceland Institute of Earth Sciences, stated that the eruption was officially over, although the area was still geothermally active and might erupt again.

During the eruption, the BBC
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