Mount St. Helens

Mount St. Helens is an active stratovolcano in Washington State. Its 1980 eruption triggered a massive north-flank landslide and lateral blast, reshaping the mountain and surrounding landscape.

Lateral blast: A sideways-directed volcanic explosion that expands rapidly from a collapsing or ruptured volcano flank. The north-flank collapse released Mount St. Helens’s pressurized magma laterally.
1980 eruption of Mount St. Helens: A sequence of volcanic events culminating in Mount St. Helens’s catastrophic eruption on May 18, 1980. It is the defining event in the volcano’s modern history.
Cascade Volcanic Arc: A chain of volcanoes in the Pacific Northwest formed above the Cascadia subduction zone. Mount St. Helens is one of the arc’s most active and closely monitored volcanoes.
David A. Johnston: A United States Geological Survey volcanologist killed while monitoring Mount St. Helens during its 1980 eruption. His observations from Coldwater II documented the volcano’s final minutes before the blast.
Ecological succession: The changing composition of an ecological community over time after disturbance or on newly available habitat. Plants and animals recolonized the eruption zone through both gradual recovery and unexpected survival.
Landslide: The downward movement of rock, soil, or debris along a slope under gravity. The volcano’s enormous landslide removed its north flank and exposed pressurized magma.
1980 Mount St. Helens ashfall: The widespread deposition of volcanic ash following Mount St. Helens’s May 1980 eruption. Ashfall carried the eruption’s effects far beyond the blast zone.
Cascadia subduction zone: A convergent plate boundary where the Juan de Fuca Plate descends beneath the North American Plate. This subduction system supplies magma to Mount St. Helens and other Cascade volcanoes.
Harry R. Truman: A lodge owner who refused to leave the Mount St. Helens hazard zone and died in the 1980 eruption. His refusal to evacuate became a lasting story of risk and attachment to place.
Mount St. Helens research: Long-term scientific studies of volcanic processes and ecological recovery at Mount St. Helens. The eruption created a rare natural laboratory for observing disturbance and ecosystem rebuilding.

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