Since Friday May 2, the Chaiten Volcano in Chile has been erupting steam and ash in a most spectacular fashion for the first time since 7400 BC. The column of ash and steam rose over 17 km high and drifted over the Andes Mountains into Argentina and over the Atlantic. The terrestrial and aerial/satelite imagery of this event is amazing and frightening. Geology.com has an excellent page covering the latest info on the Chaiten eruption.
There is concern now that the energy of the volcano has leveled off and a collapse of the ash column could happen at any time creating a pyroclastic flow of super-heated ash and vapors much like the one that buried Pompei. The photo at the left is of a lightning storm interacting with the dust and steam from the erruption, it looks like armageddon! (Photo by Carlos Gutierrez / UPV / Landov)