Lars is on a roll, so here is the follow-up to yesterday's post on seismic events in Iceland. If you did not read yesterday's post, it provides useful background info for this one.
A Recent Case History--the 2010 Eruption of Eyjafjallajökull
We initially planed to go to Iceland back in the spring of 2010, but Eyjafjallajökull (EYE-yah-fyet-lah-YO-kutl) volcano erupted on 20 May and would have greatly disrupted our trip, making much of it impossible.
Because of the extensive network of seismometers in place in Iceland, it was possible to follow the course of early seismic events related to this eruption, starting in 2006, right up to and during the actual eruption, something that was not possible previously in Iceland. See http://en.wikipedia.org/wiki/2010_eruptions_of_Eyjafjallaj%C3%B6kull. Scroll down in this report to section "SCIENTIFIC OBSERVATIONS", to 3rd paragraph, starting with the sentence "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." This and subsequent text briefly describes the results of using small earthquakes to follow the years-long development of what became an actual, highly disruptive volcanic eruption. Basically, about 250 small earthquakes were recorded in the area deep (roughly 10 km) below this volcano in the three year period from September 2006 to August 2009. By December 2009 the number of these small earthquakes had increased to thousands and were centered east of the volcano's summit crater, at a depth of 8 to 12 km. By end of December 2009, this concentration of small earthquakes had migrated upward to a depths of 7 to 10 km. By early March, thousands of these small earthquakes were centered below the volcano's crater.
In addition to the seismic data, in late February 2010 a GPS system at a nearby farm showed that the ground had been raised about 4 cm, indicating movement of magma (molten rock) into the upper parts (magma chamber) of this volcano. The eruption started on 20 March 2010.
The Meteorological Service of Iceland published a report describing the course of this volcanic eruption and how it so disrupted air travel in the North Atlantic, in England, Norway, and Europe and extensively disrupted life and damaged roads and farms in southern Iceland. http://en.vedur.is/earthquakes-and-volcanism/articles/nr/1884 This report contains many striking and informative pictures, as well as lots and lots of scientific information about the eruption. Note that two natural features, position of the jet stream directly over this volcano during the eruption and presence of a glacier on Eyjafjallajökull, greatly enhanced the disruption this eruption caused to airplane traffic. The eruption plume extended into the jet stream, which then carried volcanic ash eastward. Water melted from the glacier was converted to steam in the volcano, further increasing the vertical extent of the eruption plume.
The 2011 Grimsvötn Eruption
See http://en.wikipedia.org/wiki/Gr%C3%ADmsv%C3%B6tn for information about a similar volcanic eruption in May 2011. This eruption was at Grimsvötn (GRIMS-vuht’n), Iceland's most active volcano in recent centuries. While this eruption disrupted air traffic less than the 2010 eruption of Eyjafjallajökull, it did cause President Obama's visit to Ireland to be shortened from 24 to 12 hours.
Additional Information About Volcanic Activity on Iceland
See also http://en.wikipedia.org/wiki/Iceland_hotspot and http://en.wikipedia.org/wiki/Iceland_plume for brief overviews of the volcanic activity that has formed Iceland and ideas about the presumed driver of this activity. For the truly hardcore, here is a link to the 125-page scholarly review paper on which the Wikipedia article on the Iceland plume concept is based: http://www.dtm.ciw.edu/users/ruedas/research/iceland-reviewwww.pdf.
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