Volcanic Vetting

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Science  28 Oct 2011:
Vol. 334, Issue 6055, pp. 434
DOI: 10.1126/science.334.6055.434-a

The eruption of Eyjafjallajökull in Iceland in 2010 disrupted air travel across large parts of Europe. Just recently, a series of earthquakes has occurred beneath Katla, which has produced much larger historical eruptions. Ash from even modest volcanic eruptions can be preserved as fine layers in lake and bog sediments, and along with historical records, can provide information on likely recurrence rates. Swindles et al. provide a synthesis of these records, improved by recent dating, microscopic identification of thin ash deposits in the sedimentary sequences, and in some cases chemical fingerprinting of ash to sources. The integrated record, which is probably still missing some events, implies that ash from Icelandic eruptions spread across northern Europe on average about every 50 years during the past 1500 years, and a bit less frequently earlier. In a separate study, Taddeucci et al. examined the fallout of ash from Eyjafjallajökull and show, through direct high-speed videos and simulations, that fine-ash aggregated within the cloud, accelerating its fallout. This effect increased the amount of fine ash particles close to the vent but depleted the downstream ash cloud of fine particles by about a factor of 10. This process should be considered in modeling ash clouds, as commented on by Rose and Durant, and in assessing local health effects from eruptions.

Geology 39, 887; 891; 895 (2011).

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