These Multi-angle Imaging SpectroRadiometer (MISR) images from NASA's Terra spacecraft capture the July 22 explosion of the Mt. Etna volcano. Etna is located near the eastern coast of Sicily, to the southwest of mainland Italy. Major eruptions have been issuing from both summit and flank vents. Fine ash falling onto the Province of Catania closed the local airport, and a state of emergency was declared for the town of Nicolosi, which was threatened by lava flows from the southern flanks of the volcano.

Mt. Etna, Italy. Photo: NASA/GSFC/LaRC/JPL

Above is an image set are true-color views from the instrument's 70-degree forward-viewing camera, the vertical-viewing (nadir) camera and the 70-degree backward-viewing camera, concentrating on the area around the volcano. Each of these images covers an area of 143 by 88 kilometers (89 by 55 miles).

The image below is a full-swath view from the instrument's 70-degree backward-viewing camera; the area imaged is approximately 400 kilometers wide (about 250 miles).

Two plumes of differing compositions are seen to be emanating from Etna. The bright, brownish plume drifting southeast over the Ionian Sea is composed primarily of tiny frozen fragments of lava, known as ash. A fainter, bluish-white plume is also visible, especially near the summit, and is most apparent in the 70-degree forward view. It contains very fine droplets of water and dilute sulfuric acid. In addition to the particulate plumes visible in these images, the volcano also expels gases such as water vapor, sulfur dioxide and carbon dioxide.

Although Etna is one of the world's most studied volcanoes, it is difficult to classify, being a mixture of overlapping shield and strato volcanoes, partially destroyed by repeated caldera collapse and partially buried by younger volcanic structures. Eruptions are related to a complex tectonic situation, including subducting plates, numerous major faults intersecting at the volcano and perhaps also hot-spot volcanism.

Mt. Etna is Europe's highest (3,315 meters, 10,876 feet) and most active volcano. In ancient Greek mythology, Etna was identified with the forge of Volcan.

Mt. Etna, Italy. Photo: NASA/GSFC/LaRC/JPL