The 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 ...