Can volcanoes be dangerous even when they don't erupt?

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Mt. Rainier and a volcanic debris flow that started at Emmons Glacier. Image Credit: USGS
Information on this page was collected from the source acknowledged below:

From the U.S. Geological Survey Volcano Hazards Program FAQs:

"Definitely. Many stratovolcanoes have a plumbing system of hot acid water that progressively breaks down hard rock to soft, clay-rich material. The volcano is gradually weakened, and large parts may suddenly fail. Resulting water-rich landslides are especially dangerous because they can occur without any volcanic or seismic warning.

The risk of mudflows [lahars] formed this way is especially high along rivers downstream from Mount Rainier, because of the large population on floodplains, the huge weakened edifice of the volcano, and a long history of large flows that occurred when the volcano was otherwise dormant."

Learn More

  • Volcanoes and Lahars (Website), Washington Department of Natural Resources
    Resources to learn more about volcanoes, their hazards, who is at risk, and how to prepare for emergencies. Particular focus on volcanoes in Washington.
  • Investigating Volcanic Landslide Hazards (Case Study), American Geosciences Institute
    Case study demonstrating how modern surveying methods are used to assess volcanic landslide and debris flow hazards