2011 eruption of Grímsvötn

The 2011 eruption of Grímsvötn was a Plinian eruption of Grímsvötn, Iceland's most active volcano, which caused disruption to air travel in Northwestern Europe from 22–25 May 2011. The last eruption of Grímsvötn was in 2004, with the previous most powerful eruptions in 1783, 1873 and 1902. The Grímsvötn eruption was the largest eruption in Iceland for 50 years.

Timeline

The eruption is estimated to have started under the glacier at around 17:30 UTC on 21 May 2011 when an intense spike in tremor activity was detected. At around 19:00 UTC, the eruption broke the ice cover of the glacier and started spewing volcanic ash into the air. The eruption plume quickly rose to . A series of small earthquakes had commenced at the time of eruption. Glacial flooding was anticipated, which normally occurs within 10–12 hours after eruption, but it never occurred as a flood had occurred the previous autumn, meaning a smaller chance of another flood appearing.

On 25 May, the Icelandic Meteorological Office (IMO) confirmed the eruption had paused at 02:40 UTC. Later the BBC reported that the volcanic activity appeared to have stopped. At 15:00 the IMO issued an update stating that no further ash plume was expected. Pulsating explosions continued to produce ash and steam clouds, some reaching a few kilometers in height, rising up from the vents. There was widespread ash in cloud layers up to 5 km from the eruption site.

On 26 May the IMO and the University of Iceland reported that ashfall was only occurring adjacent to the eruption site. Visual observations indicated that little ice meltwater was produced during the eruption, so that an outburst flood (jökulhlaup) was not expected.

The eruption ceased at 7am on 28 May 2011.

Ash characteristics

The ash content from the Grímsvötn volcano in Iceland had a much lower silica content (50%) compared to the ash from the 2010 eruptions of Eyjafjallajökull (63%), giving the latter a higher viscosity. The ash emitted from Grímsvötn is also more coarse than the smaller, more abrasive particles emitted from the Eyjafjallajökull eruption as a result of the basalt-based magma of the Grímsvötn volcano exploding through the glacier, rather than reacting with meltwater.

Effect on flights

A total of 900 flights (out of 90,000 in Europe) were cancelled as a result of the eruption in the period 23–25 May.

On 22 May, Iceland closed down its main airport Keflavík International Airport, with domestic flights operated from Reykjavík Airport cancelled as well. Transatlantic flights had also experienced delays, and the threat of further air travel disruption cut US President Barack Obama's state visit to Ireland a day short. Part of Greenland's eastern airspace was also closed, with one flight being cancelled by Air Greenland between Denmark's Kastrup Airport and Greenland's Kangerlussuaq Airport.

By 23 May, authorities in Denmark closed airspace below in the northwestern part of the country, with some delays and cancellations at Copenhagen.

On 24 May, more than 1,600 flights were grounded as ash clouds travelled over Scotland, with airports in Scotland and northern England closed and 250 UK flights grounded. British Airways, KLM, Aer Lingus, Flybe, BMI, Loganair, Eastern Airways, EasyJet, and Ryanair cancelled most flights in the Scotland region, seeing Wales' Cardiff Airport also cancelling inbound and outbound flights by airline Flybe. Certain flights from Northern Ireland were also grounded. The BBC
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