How many eruptions have there been in the Cascades during the last 4,000 years?

Eruptions in the Cascades have occurred at an average rate of one to two per century during the last 4,000 years. Future eruptions are certain.

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How would an eruption of Mount Rainier compare to the 1980 eruption of Mount St. Helens?

Eruptions of Mount Rainier usually produce much less volcanic ash than do eruptions at Mount St. Helens . However, owing to the volcano's great height and widespread cover of snow and glacier ice, eruption-triggered debris flows ( lahars ) at Mount Rainier are likely to be much larger--and will travel a greater distance--than those at Mount St...

How dangerous is Mount Rainier?

Although Mount Rainier has not produced a significant eruption in the past 500 years, it is potentially the most dangerous volcano in the Cascade Range because of its great height, frequent earthquakes , active hydrothermal system , and extensive glacier mantle. Mount Rainier has 26 glaciers containing more than five times as much snow and ice as...

How old is Mount St. Helens?

The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago. This activity included numerous explosive eruptions over periods of hundreds to thousands of years, which were separated by apparent dormant intervals ranging in length from a few hundred to...

How far did the ash from Mount St. Helens travel?

The May 18, 1980 eruptive column at Mount St. Helens fluctuated in height through the day, but the eruption subsided by late afternoon. By early May 19, the eruption had stopped. By that time, the ash cloud had spread to the central United States. Two days later, even though the ash cloud had become more diffuse, fine ash was detected by systems...

Do earthquakes large enough to collapse buildings and roads accompany volcanic eruptions?

Not usually. Earthquakes associated with eruptions rarely exceed magnitude 5, and these moderate earthquakes are not big enough to destroy buildings and roads. The largest earthquakes at Mount St. Helens in 1980 were magnitude 5, large enough to sway trees and damage buildings, but not destroy them. During the huge eruption of Mount Pinatubo in...

Why is it important to monitor volcanoes?

The United States and its territories contain 169 geologically active volcanoes, of which 54 volcanoes are a high threat or very high threat to public safety. Many of these volcanoes have erupted in the recent past and will erupt again in the foreseeable future. As populations increase, areas near volcanoes are being developed and aviation routes...

When did Lassen Peak last erupt?

The most recent eruptive activity at Lassen Peak (California) took place in 1914-1917. This eruptive episode began on May 30, 1914, when a small phreatic eruption occurred at a new vent near the summit of the peak. More than 150 explosions of various sizes occurred during the following year. By mid-May 1915, the eruption changed in character; lava...

How often does Mount Shasta erupt?

USGS scientists are currently working on this question. Mount Shasta doesn’t erupt on a regular timescale. Research indicates that the volcano erupts episodically with ten or more eruptions occurring in short (500-2,000 year) time periods separated by long intervals (3,000-5,000 years) with few or no eruptions. Evidence suggests that magma most...

What was the largest volcanic eruption in the 20th century?

The world's largest eruption of the 20th century occurred in 1912 at Novarupta on the Alaska Peninsula. An estimated 15 cubic kilometers of magma was explosively erupted during 60 hours beginning on June 6th. This volume is equivalent to 230 years of eruption at Kilauea (Hawaii) or about 30 times the volume erupted by Mount St. Helens (Washington...

Will extinct volcanoes on the east coast of the U.S. erupt again?

No. The geologic forces that generated volcanoes in the eastern United States millions of years ago no longer exist. Through plate tectonics, the eastern U.S. has been isolated from the global tectonic features (tectonic plate boundaries and hot spots in the mantle), that cause volcanic activity. So new volcanic activity is not possible now or in...

Which volcanoes in the conterminous United States have erupted since the Nation was founded?

Excluding steam eruptions, these volcanoes have shown activity: Mount St. Helens, Washington - Eruptions and/or lava dome growth occurred in the late 1700s, 1800-1857, 1980-1986, and 2004-2007. Lassen Peak, California - A series of steam blasts began on May 30, 1914. An eruption occurred 12 months later on May 21, 1915. Minor activity continued...

Where does the United States rank in the number of volcanoes?

The United States ranks third, behind Indonesia and Japan, in the number of historically active volcanoes (that is, those for which we have written accounts of eruptions). In addition, about 10 percent of the more than 1,500 volcanoes that have erupted in the past 10,000 years are located in the United States. Most of these volcanoes are found in...
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February 22, 2018

PubTalk 2/2018 — USGS Cascades Volcano Observatory

Title: The USGS Cascades Volcano Observatory - Research, monitoring, and the science of preparing society for low-probability, high-consequence events

  • Volcanoes in the Cascade Range erupt twice per century on average, with eruptions often lasting for years.
  • Although eruptions are generally not as high-consequence as large earthquakes, they are still
Attribution: Natural Hazards
Lassen Peak Eruption
April 18, 2016

Lassen Peak Eruption

Large snow-covered, cone shaped mountain in background, looming over urban area in foreground
January 18, 2014

Mount Rainier looms over the Puyallup Valley, Washington

Mount Rainier volcano looms over Puyallup Valley, near Orting, Washington.

video thumbnail: Volcano Hazards
July 30, 2012

Volcano Hazards

The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.

Video Sections:

  • Volcanoes: Monitoring Volcanoes
video thumbnail: The 20th Century's Greatest Volcanic Eruption- Mt Katmai 100 Years Later 
June 5, 2012

The 20th Century's Greatest Volcanic Eruption- Mt Katmai 100 Years Later 

Bill Burton discusses the June 6-8, 1912 eruption of Mount Katmai in Alaska which was 30 times larger than the eruption of Mt. St. Helens in 1980. This eruption caused widespread devastation, and inspired heroic efforts at survival by the local people. Burton returns to this topic a century later and explains what lessons the Mount Katmai eruption provides for modern-day

Attribution: Natural Hazards
May 9, 2012

Volcano Web Shorts 2: Debris Flows

Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon. Spectacular debris flow footage, recorded by Franck Lavigne of the

Image of Mount Adams with grassland and trees
December 31, 2011

Mount Adams, WA

A photograph of Mount Adams, Washington. This image was taken as part of the Land Cover Trends Project field varification for land cover data. 

mount hood
December 16, 2010

Mount Hood, OR

View of Mount Hood from Pittock Mansion, Portland, OR.

video thumbnail: Mount St. Helens: May 18, 1980
May 10, 2010

Mount St. Helens: May 18, 1980

USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens. Loss of their colleague David A. Johnston and 56 others in the eruption cast a pall over one of the most dramatic geologic moments in American history.

May 10, 2010

Mount St. Helens: A Catalyst for Change

The May 18, 1980 eruption of Mount St. Helens triggered a growth in volcano science and volcano monitoring. Five USGS volcano observatories have been established since the eruption. With new technologies and improved awareness of volcanic hazards USGS scientists are helping save lives and property across the planet.

December 31, 2006

Mount St. Helens 2004-2008 Eruption: A Volcano Reawakens

Mount St. Helens reawakened in late September 2004. Small magnitude earthquakes beneath the 1980-1986 lava dome increased in frequency and size, and a growing welt formed on the southeast margin of the previous lava dome and nearby portions of Crater Glacier. On October 1, 2004, the first of several explosions shot a plume of volcanic ash and gases from a vent on the