How were the forests at Mount St. Helens influenced by the eruption?
The 1980 eruptions of Mount St. Helens blew down or scorched 230 square miles (500 square km) of forest. The catastrophic failure of the volcanos summit and topographic channeling of the lateral blast produced a complex gradient of disturbance that ranged from complete scouring and burial by high temperature material in the Spirit Lake basin to a dusting of volcanic ash that fell on forests northeast of the blast zone. The massive size of the 230 square mile blast zone as seen from space is revealed in this 1980 false color composite image from the Landsat MSS satellite. [Landsat, MSS Composite, 1980] For purposes of description the gradient is simplified into six discrete disturbance zones. The following is a brief description of each zone starting with the most heavily disturbed surfaces closest to the volcano and then working outward toward the margins of the blast zone where disturbance was less and more organisms survived. Pyroclastic flow: Hot pumice and gas flowed down the north
