Digital terrain models of Spirit Lake blockage and Mount St. Helens debris avalanche, based on 1980-2018 airborne photogrammetry surveys
The lateral blast, debris avalanche, pyroclastic flows, and lahars of the May 18th, 1980, eruption of Mount St. Helens, Washington, dramatically altered the surrounding landscape. The debris avalanche and pyroclastic flows filled upper North Fork Toutle River valley and blocked the outlet of Spirit Lake. To mitigate …