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Powerful Eruption at Iceland’s Grimsvotn

May 22, 2011, by Ken Jorgustin

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Ash could begin to reach parts of Scotland as early as Tuesday followed by Britain, France, and Spain while a powerful Icelandic volcano named Grimsfjall (also known as Grimsvotn) continues to erupt there at the Vatnajökull ice cap (Europe’s largest glacier).

One insider said, “There was no warning at all…approximately 20 minutes from first quake to eruption,” “First estimations show this is 10x larger than the 2004 eruption.” There were some expectations that the next eruption at Grimsfjall/Grimsvotn would be stronger, due to increased bulging inflation in the area, but the powerful explosion and ash plume reaching as high as 25 km, caught many out.

A curious observation followed the initial quake swarm and eruption – Once the magma reaches the surface, the quakes typically stop. With Grimsfjall/Grimsvotn, another earthquake swarm persisted to the east. There is also renewed earthquake activity to the south, at the Katla volcano region, which itself is a time-bomb waiting to unleash its fury.

Locally, the immediate threat is ash-fall, which this time is of a heavy consistency. Threats of glacial water flooding persist due to the intense volcanic heat melting the ice.

Further away, European air traffic control are working with Meteorology Offices to determine the path of the ash cloud and the impact it may have on European air traffic this week. One year ago, much of European air traffic was shut down for 6 days from another Icelandic volcano that blew its top (Eyjafjallajokull), leaving countless stranded travelers and a dent in the economy.

Magnus Tumi Gudmundsson, Professor of Geophysics at the University of Iceland, said “We see some signs that the power is declining a bit, but it is still quite powerful,” and also said that the eruption was the most violent at the volcano since 1873.

The potential disruption during the upcoming week will depend on the atmospheric wind patterns, and the ongoing strength of the eruption itself.

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Spectacular Image of Grimsfjall – Grimsvotn Eruption, Ash Plume
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Update: 23-May-2011

Icelandic Meteorological Office and Institute of Earth Sciences, University of Iceland

Eruption Plume Height (a.s.l.): The ash plume reached heights of 8 to 10 km last night and this morning. In the last hours, the plume has reached heights of 5 to 9 km, but northerly winds have been very strong which can effect the height.

Eruption Plume Heading: Most of the ash cloud heads to the south. At altitudes of 8 km and higher, part of the plume heads to the west.

Eruption Plume Colour: Brown- or grayish and sometimes black close to the eruption site.

Tephra fallout: The amount of fallout is great from Vík in the west to the east of Öræfajökull. The amount of ash fall is the greatest close to the village Kirkjubæjarklaustur. Ash has been detected in several areas throughout the country, except in the northwest. A sample from Kirkjubæjarklaustur has been analyzed, which was taken around 1h on 22 May. The grains are glassy with micro crystals of plagioclase. Samples well sorted. Whole rock analysis: Basalt, with 50-51 Wt% SiO2 Leachate results: 5-10 mg/kg of waterdissolvable flour Grain size distribution: about 10% of the volume of the analyzed samples is finer than 10 micrometers Lightning: From 17-18h yesterday, about 300 lightning strikes were detected but much less thereafter. The strikes were most frequent south of Grímsvötn.

Noise: No noise from the volcano has been reported.

Meltwater: No changes in water level have been recorded in the rivers Gígja and Núpsvötn. Since the eruption is practically at the same site inside the Grímsvötn caldera as the last eruption, ice-melt is not expected to be great and therefore swelling of rivers in the next few days is not
expected. Conditions at eruption site: The eruption site is in the southwest corner of the Grímsvötn caldera, in the same site as the 2004 eruption. The basaltic magma is fragmented into tephra in violent magma-water interaction. Very powerful explosions occur at the eruption site.

Seismic tremor: Seismic tremor at the Grímsfjall station was fairly stable last night. After midnight andtoday, the tremor levels have been fluctuating and decreasing slightly.

Earthquakes: No earthquakes have been recorded in the volcano since yesterday afternoon.

GPS deformation: Rapid deformation was detected at the CGPS station Grimsvotn (GFUM) in the first hours of the eruption. GFUM is located 5 km east of the eruption site. In the first four hours the site moved ~ 20 cm in the north direction, 15 cm towards west and subsided 10 cm. The deformation rate has since slowed down, with the total displacement in the first two days of the eruption about 50 cm to the northwest, with 25 cm subsidence. These displacements are ~60% larger than comparable measurements made after the 1998 and 2004 eruptions of Grímsvötn.

Overall assessment: The eruption has abated slightly since yesterday. No effusion of lava has been observed.



Stunning Video of Grimsvotn Eruption put to music
Credit: Jon Gustafsson
Music: Veigar Margeirsson
Pilot: Reynir Petursson
Helicopter Service of Iceland
[vimeo]http://vimeo.com/24084400[/vimeo]



Update: 24-May-2011
First statistics show that in the first 3 days of the Grímsvötn eruption, output had already surpassed the total output of Eyjafjallajokull (VEI 4). Eyes are currently on Katla (Godabunga – west side) where there is some activity, however this may not be related to the new activity of Grimsvotn. We’ll see.



Update: 25-May-2011
Yesterday evening there was still active explosivity in Grímsvötn. The activity is in three to four tephra cones surrounded by meltwater. The activity is pulsating with explosions producing ash clouds that rise up from the craters, some reaching a few km. The eruption plume is not continuous and all the material falls out nearby.

Today:
Eruption has stopped for now but unlikely to be over. Many things going on in and adjacent to the eruption site that leads to the conclusion that it’s not over yet.



Update: 26-May-2011
“Tremor plots show activity as if an eruption is still ongoing. What this means area is still very active but also could be due to deflation and hydrothermal activity.”



Update: 28-May-2011
Activity is very minimal at the moment and tremor plot has dropped. This could mean it’s over.

See Grimsvotn Volcano web cam for live info http://live.mila.is/grimsvotn2/

If you have wondered why is it called Grímsfjall and Grimsvotn. Grímsfjall is the main volcano and is under the ice sheet. The fjall means mountain and votn means lake.



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