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While volcanoes are certainly one of California's most prominent natural hazards, they are by far one of the least common. Seasonal hazards such as...

Debris flows or mudflows that form from volcanic material are called lahars. The word lahar comes from Javanese, the language spoken on the island of...

Photographs can be a huge help in interpreting the mechanics and timelines of volcanic eruptions. For example, he 1914–1917 eruptions of Lassen Peak...

"An avalanche of mud...covering the countryside like a tidal wave."

A short earthquake swarm in the southern part of the Lassen Volcanic Center reminds us that volcanoes can shake, rattle, and roll even when they're...

Before there was a California Volcano Observatory or even a Long Valley Observatory, a tiny cabin in northern California housed the first full-time...

Since May 11, 2023, a series of M5+ earthquakes and aftershocks have rattled the area around Lake Almanor, a reservoir about 20 miles (32 km)...

How does hot water bring down volcanic slopes?

If you've noticed any changes to the earthquake counts released in CalVO's weekly updates, don't worry - some behind-the-scenes improvements to our...

USGS Volcanic Threat Assessment updates the 2005 rankings.