Icelandís Grimsvotn Volcano

On May 21, 2011, Icelandís Grimsvotn Volcano erupted, sending an ash plume 12 miles (20 kilometers) high and closing Keflavik Airport, Icelandís largest. Ash fell on much of Iceland, with some areas pitch black at midday on the 22nd. This eruption is not expected to disrupt air travel as much as taht of Eyjafjallajokull in 2010 because the Grimsvotn ash particles are larger and settling out of the atmosphere more quickly.

This natural-color satellite image, acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite, shows the towering ash plume at 1:00 p.m. local time. Beneath the ash plume, clouds cover much of the scene. Lingering snow is visible beneath the clouds to the northeast (upper left). Brown ash covers a portion of the Vatnajokull Glacier near the Atlantic coast (lower right).

Grimsvotn is Icelandís most active volcano, but it hasnít erupted so forcefully since 1902. The lava is basaltic, which typically erupts in non-explosive, Hawaiian-style eruptions. Grimsvotn is located beneath a glacier, however, and the interaction of melting ice with the lava can create an explosive eruption, at least in the initial stages.