nThe steam-and-ash plume from Eyjafjallajokull in Iceland, March 22, 2010.
Overnight, the Eyjafjallajokull eruption in Iceland added to its oeuvre, producing what is being reported to be a 8-km plume. Images of the plume (above) suggest (to me) that it is very water-rich, so likely this is the expanding(?) fissure interacting with snow, ice or groundwater, producing steam explosions. These explosions have some minor ash component to them, mostly from the shattering of rapidly cooled lava, but are dominated by steam.
The eruption appears to be continuing into its third day unabated. Flights have resumed to and from Iceland as well. Minus the phreatomagmatic explosions of earlier today, the eruption has been relatively passive (in the grand scheme of volcanic eruptions) and the hazard of ash at high altitudes right now is low. However, many things can change quickly. The AP has posted a little bit more daylight footage from the eruption, showing the pulsing fire fountains along the fissure vent. There have also been some nice, sensational headline like “Eruption of Dormant Volcano Causes Panic in Iceland” (the evacuations actually seem to be calm) and “Iceland will maybe get blown up by huge volcano soon” (OK, so that was from Gawker), but on the whole, the coverage of the Icelandic eruption has been fairly calm and rational.
Here is the official press release from the Nordic Volcanological Center and Icelandic Meteorological Office:
An eruption began in South Iceland in late evening of 20 March 2010 at the
nEyjafjallajökull volcanic system (also known as Eyjafjöll volcano – Global
nVolcanism Program Volcano number 1702-02=). The initial visual report of
nthe eruption was at 23:52 GMT, when a red cloud was observed at the
nvolcano, lightening up the sky above the eruptive site. The eruption was
npreceded with intense seismicity and high rates of deformation in the
nweeks before the eruption, in association with magma recharging of the
nvolcano. Immediately prior to the eruption the depth of seismicity had
nbecome shallow, but was not significantly enhanced from what it had been
nin the previous weeks. Deformation was occurring at rates of up to a
ncentimetre a day since March 4 at continuous GPS sites installed within 12
nkm from the eruptive site.
The eruption broke out with fire fountains and Hawaiian eruptive style on
nabout 500 m long NE-SW oriented eruptive fissure at N63º 38.1′, W19º
n26.4′ on the northeast shoulder of the volcano at an elevation of
nabout 1000 m. It was observed from air from 4-7 A.M. on March 21. Lava
nflows short distance from the eruptive site, and minor eruption plume at
nelevation less than 1 km was deflected by wind to the west. Volcanic
nexplosive index (VEI) is 1 or less. Tephra fall is minor or insignificant.
nThe eruption occurs just outside the ice cap of Eyjafjallajökull, and no
nice melting is occurring at present.
Satellite data is being used to study the eruption and associated
nintrusion. Several MODIS thermal images on 21 March show a temperature
nanomaly where the eruption is occurring. ENVISAT ASAR images before and
nduring the eruption have been acquired, and a series of TerraSAR-X images
ncover the area.
The eruption is located on about 2 km wide pass of ice-free land between
nEyjafjallajökull and the neighbouring Katla volcano with its overlying
nMyrdalsjökull ice cap. Katla volcano is known for powerful subglacial
nphreatomagmatic eruptions producing basaltic tephra layers with volumes
nranging from ~0.01 to more than 1 cubic kilometer.
Three previous eruptions of Eyjafjallajökull are known in the last 1100
nyears (historical time in Iceland). The most recent began in December 1821
nand lasted intermittently for more than a year. The neighbouring volcano
nKatla erupted then on 26 June 1823. Other eruptions include an eruption in
n1612 or 1613, and about 920 A.D.
Episodes of unrest are known at Eyjafjallajökull, with documented sill
nintrusions in 1994 and 1999.
For information see:
and the following references:
nSturkell, E., P. Einarsson, Freysteinn Sigmundsson, A. Hooper, B. G.
nÓfeigsson, H. Geirsson and H. Ólafsson, Katla and Eyjafjallajökull
nvolcanoes, In: The Mýrdalsjökull Ice cap, Iceland – Glacial processes,
nsediments and landforms on an active volcano. Developments in Quaternary
nSciences, vol., 13, eds. Anders Schomacker, Johannes Krüger and Kurt H.
nKjær, p. 5-21, 2009.
Hjaltadottir, S., K. S. Vogfjord and R. Slunga, 2009. Seismic signs of
nmagma pathways through the crust at Eyjafjallajokull volcanoe, South
nIceland, Icelandic Meteorological office report, VI 2009-013
Hooper, A., R. Pedersen, F. Sigmundsson, Constraints on magma intrusion at
nEyjafjallajökull and Katla volcanoes in Iceland, from time series SAR
ninterferometry, In: The VOLUME project – Volcanoes: Understanding
nsubsurface mass movement, eds. C. J. Bean, A. K. Braiden, I. Lokmer, F.
nMartini, G. S. O’Brien, School of Geological Sciences, University College
nDublin, p. 13-24, 2009
Larsen, G., 1999. Gosið í Eyjafjallajökli 1821-1823 (The eruption of the
nEyjafjallajökull volcano in 1821-1823). Science Institute Research Report
nRH-28-99. 13 p. Reykjavík.
Oskarsson, Birgir Vilhelm 2009. The Skerin ridge on Eyjafjallajökull,
nSouth Iceland: Morphology and magma-ice interaction in an ice-confined
nsilicic fissure eruption. M.Sc. thesis, Faculty of Earth Sciences,
nUniversity of Iceland. 111 p.
Pedersen, R., Freysteinn Sigmundsson and Páll Einarsson, 2007: Controlling
nfactors on earthquake swarms associated with magmatic intrusions;
nConstraints from Iceland, Journal of Volcanology and Geothermal
Pedersen, R., Sigmundsson, F., Temporal development of the 1999 intrusive
nepisode in the Eyjafjallajökull volcano, Iceland, derived from InSAR
nimages, Bull. Volc., 68, 377-393, 2006.
Pedersen, R., F. Sigmundsson, InSAR based sill model links spatially
noffset areas of deformation and seismicity for the 1994 unrest episode at
nEyjafjallajökull volcano, Iceland, Geophys. Res. Lett., 31, L14610,
Sigmundsson, F., Geirsson, H., Hooper, A. J., Hjaltadottir, S., Vogfjord,
nK. S., Sturkell, E. C., Pedersen, R., Pinel, V., Fabien, A., Einarsson, P.
nGudmundsson, M. T., Ofeigsson, B., Feigl, K., Magma ascent at coupled
nvolcanoes: Episodic magma injection at Katla and Eyjafjallajökull
nice-covered volcanoes in Iceland and the onset of a new unrest episode in
n2009, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract V32B-03