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Scientists Name Mt Rainier America's Most Dangerous Volcano

natureJun 4, 2026·347 words·3 min read

Scientists are warning that Mount Rainier, a 14,000-foot peak in Washington State, is the most dangerous volcano in the United States, even though its molten rock has not erupted in centuries. The greatest threat, they say, is not lava but a lahar — a violent slurry of rock, mud, and meltwater that can flow downhill at over 100 miles per hour.

Lahars do not need a volcanic eruption. Heavy rain, a sudden warm spell, or a broken dam can start one. Mount Rainier has 25 large glaciers — slow rivers of ice. They hold more than five times as much ice as all other Cascade volcanoes combined. So a small amount of melting can cause a huge lahar. The wall of mud can grow hundreds of feet tall and travel over 50 miles.

This danger is real. In 1985, a lahar from a volcano in Colombia killed more than 23,000 people in just minutes. To stop the same thing happening here, the Cascades Volcano Observatory (CVO) has placed special sensors to detect lahars and earthquakes. Two years ago, over 45,000 students and staff joined a huge evacuation drill. They learned that running uphill on foot is the best way to stay safe.

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