The USGS provides monitoring updates, data, images, and preparedness tips about volcanoes throughout the United States and U.S. territories through the Volcano Hazards Program (VHP). The mission of the VHP is to enhance public safety and minimize social and economic disruption from volcanic unrest and eruption through their National Volcano Early Warning System. The VHP delivers forecasts, warnings, and information about volcano hazards based on a scientific understanding of volcanic behavior. Volcanic eruptions occur roughly 100-2000 years.
There are 170 potentially active volcanoes in the United States. All volcanoes in the Cascade Range of Oregon and Washington (Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, Mount Adams, Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake) are at normal background activity levels.
Below is a diagram of historical volcanic eruptions in the Oregon, Washington, and northern California over time.
(Content and image from the USGS)
At 8:32 Sunday morning, May 18, 1980, Mount St. Helens erupted, shaken by an earthquake measuring 5.1 on the Richter scale, the north face of this tall symmetrical mountain collapsed in a massive rock debris avalanche. This slab of rock and ice slammed into Spirit Lake, crossed a ridge 1,300 feet high, and roared 14 miles down the Toutle River.
The avalanche rapidly released pressurized gases within the volcano. A tremendous lateral explosion ripped through the avalanche and developed into a turbulent, stone-filled wind that swept over ridges and toppled trees. Nearly 150 square miles of forest was blown over or left dead and standing.
A mushroom-shaped column of ash rose thousands of feet skyward and drifted downwind, turning day into night as dark, gray ash fell over eastern Washington and beyond. Wet, cement-like slurries of rock and mud scoured all sides of the volcano. Searing flows of pumice poured from the crater. The eruption lasted 9 hours, but Mount St. Helens and the surrounding landscape were dramatically changed within moments. A vast, gray landscape lay where once the forested slopes of Mount St. Helens grew.
In 1982 the President and Congress created the 110,000-acre National Volcanic Monument for research, recreation, and education. Inside the Monument, the environment is left to respond naturally to the disturbance.
The USGS has several volcano observatories stationed throughout the Pacific Northwest, in addition to Alaska and Hawaii. Learn more about the observatories at the Cascade Volcano Observatory (CVO) site.