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2h ago

Mount St. Helens, 46 Years Later, Is Quiet Under Watch

Expanded sensors give early warning that supports a continued green alert.

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360995 06: A cloud of ash covers a mountaintop May 22, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
In this May 18, 1980, file photo, Mount St. Helens sends a plume of ash, smoke and debris skyward as it erupts. On that day, the Mount St. Helens volcano in Washington state exploded, leaving 57 people dead or missing.
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Overview

  • The 46th anniversary observed Monday marks the deadliest and most destructive U.S. eruption, with 57 people killed and 230 square miles of forest flattened.
  • A magnitude 5.1 quake set off the north face collapse and the largest landslide on record, driving a lateral blast and an ash column reported up to 80,000 feet.
  • The USGS reports activity at background levels under a green alert, and says a September 2025 ash cloud was old material lofted by wind rather than new unrest.
  • Monitoring now forms one of the densest networks in the Cascades, with about 18 seismometers within seven miles and more than 20 stations on and around the volcano.
  • A 2014 project that deployed roughly 3,500 seismic sensors mapped linked magma zones beneath the mountain, giving scientists better data to spot changes before future eruptions.