The May 18, 1980, eruption of Mount St. Helens came after two months of small earthquakes. During the eruption, an avalanche of debris and mud spread for miles from the former summit, and a blast of steam and hot ash covered an area of about 600 km2 (230 mi2). In the decades since, scientists have studied the recovery of the ecosystem around the mountain using the Landsat series of satellites. By observing different wavelengths of light reflected of the surface, Landsat data can identify differe