Felt earthquakes on Mount Hood (Oregon) occur every two years on average. Seismic monitoring, in effect since 1977, indicates a generalized concentration of earthquakes just south of the summit area and 2-7 kilometers below sea level. A seismic swarm in July 1980, during which nearly 60 earthquakes (mostly 5-6 kilometers deep with a maximum bodywave magnitude of 2.8) were recorded in a 5-day period, prompted development of an emergency response plan to coordinate local authorities in the event of a future eruption.
Related Content
Does Portland, Oregon have a volcano within its metropolitan area?
The town of Portland, Oregon does have most of a Pliocene-Pleistocene volcanic field within its metropolitan boundaries. The Boring Volcanic Field consists of more than 80 cinder cones and small shield volcanoes. The youngest volcano (Beacon Rock) in the Volcanic Field erupted about 57,000 years ago. Since activity began in this area 2.6 million years ago, it is rare for 50,000 years to pass...
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 25 major glaciers containing more than five times as much snow and ice as all the other Cascade volcanoes combined. If...
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. Learn more: Eruptions in the Cascade Range During the Past 4,000 Years USGS Cascades Volcano Observatory
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. Helens in 1980. Furthermore, areas at risk from debris...
What is the greatest hazard presented by Mount Rainier?
Debris flows (lahars) pose the greatest hazard to people near Mount Rainier. A debris flow is a mixture of mud and rock debris that looks and behaves like flowing concrete. Giant debris flows sometimes develop when large masses of weak, water-saturated rock slide from the volcano's flanks. Many of these debris flows cannot be predicted and may even occur independently of a volcanic eruption. Giant...
What is the origin of the name "Mount St. Helens"?
Some Indians of the Pacific Northwest variously called Mount St. Helens 'Louwala-Clough,' or 'smoking mountain.' The modern name, Mount St. Helens, was given to the volcanic peak in 1792 by seafarer and explorer Captain George Vancouver of the British Royal Navy. He named it in honor of fellow countryman Alleyne Fitzherbert, who held the title ‘Baron St. Helens’. Fitzherbert at the time served 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 about 15,000 years. The range of rock types erupted by...
How much ash was there from the May 18, 1980 eruption of Mount St. Helens?
During the 9 hours of vigorous eruptive activity on May 18, 1980, about 540 million tons of ash from Mount St. Helens fell over an area of more than 22,000 square miles (57,000 square kilometers). The total volume of the ash before its compaction by rainfall was about 0.3 cubic mile (1.3 cubic kilometers), equivalent to an area the size of a football field piled about 150 miles (240 kilometers)...
How high was Mount St. Helens before the May 18, 1980 eruption? How high was it after?
Before May 18, 1980, Mount St. Helens' summit altitude of 9,677 feet (2,950 meters) made it only the fifth highest peak in Washington State. It stood out handsomely, however, from surrounding hills because it rose thousands of feet above them and had a perennial cover of ice and snow. The peak rose more than 5,000 feet (1,524 meters) above its base, where the lower flanks merge with adjacent...
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 used to monitor air pollution in several cities of...
When volcanoes fall down—Catastrophic collapse and debris avalanches
2018 update to the U.S. Geological Survey national volcanic threat assessment
U.S. Geological Survey Volcano Hazards Program—Assess, forecast, prepare, engage
Volcanoes!
Airborne volcanic ash; a global threat to aviation
Eruptions in the Cascade Range during the past 4,000 years
Volcano hazards— A national threat
Volcano hazards in the Mount Hood region, Oregon
Living with volcanoes
Related Content
- FAQ
Does Portland, Oregon have a volcano within its metropolitan area?
The town of Portland, Oregon does have most of a Pliocene-Pleistocene volcanic field within its metropolitan boundaries. The Boring Volcanic Field consists of more than 80 cinder cones and small shield volcanoes. The youngest volcano (Beacon Rock) in the Volcanic Field erupted about 57,000 years ago. Since activity began in this area 2.6 million years ago, it is rare for 50,000 years to pass...
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 25 major glaciers containing more than five times as much snow and ice as all the other Cascade volcanoes combined. If...
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. Learn more: Eruptions in the Cascade Range During the Past 4,000 Years USGS Cascades Volcano Observatory
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. Helens in 1980. Furthermore, areas at risk from debris...
What is the greatest hazard presented by Mount Rainier?
Debris flows (lahars) pose the greatest hazard to people near Mount Rainier. A debris flow is a mixture of mud and rock debris that looks and behaves like flowing concrete. Giant debris flows sometimes develop when large masses of weak, water-saturated rock slide from the volcano's flanks. Many of these debris flows cannot be predicted and may even occur independently of a volcanic eruption. Giant...
What is the origin of the name "Mount St. Helens"?
Some Indians of the Pacific Northwest variously called Mount St. Helens 'Louwala-Clough,' or 'smoking mountain.' The modern name, Mount St. Helens, was given to the volcanic peak in 1792 by seafarer and explorer Captain George Vancouver of the British Royal Navy. He named it in honor of fellow countryman Alleyne Fitzherbert, who held the title ‘Baron St. Helens’. Fitzherbert at the time served 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 about 15,000 years. The range of rock types erupted by...
How much ash was there from the May 18, 1980 eruption of Mount St. Helens?
During the 9 hours of vigorous eruptive activity on May 18, 1980, about 540 million tons of ash from Mount St. Helens fell over an area of more than 22,000 square miles (57,000 square kilometers). The total volume of the ash before its compaction by rainfall was about 0.3 cubic mile (1.3 cubic kilometers), equivalent to an area the size of a football field piled about 150 miles (240 kilometers)...
How high was Mount St. Helens before the May 18, 1980 eruption? How high was it after?
Before May 18, 1980, Mount St. Helens' summit altitude of 9,677 feet (2,950 meters) made it only the fifth highest peak in Washington State. It stood out handsomely, however, from surrounding hills because it rose thousands of feet above them and had a perennial cover of ice and snow. The peak rose more than 5,000 feet (1,524 meters) above its base, where the lower flanks merge with adjacent...
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 used to monitor air pollution in several cities of...
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When volcanoes fall down—Catastrophic collapse and debris avalanches
Despite their seeming permanence, volcanoes are prone to catastrophic collapse that can affect vast areas in a matter of minutes. Large collapses begin as gigantic landslides that quickly transform to debris avalanches—chaotically tumbling masses of rock debris that can sweep downslope at extremely high velocities, inundating areas far beyond the volcano. Rapid burial by the debris avalanches them2018 update to the U.S. Geological Survey national volcanic threat assessment
When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location. Assessing the relative threats posed by U.S. volcanoes identifies which volcanoes warrant the greatest risk-mitigation efforts by the U.S. Geological Survey and its partners. This updateU.S. Geological Survey Volcano Hazards Program—Assess, forecast, prepare, engage
At least 170 volcanoes in 12 States and 2 territories have erupted in the past 12,000 years and have the potential to erupt again. Consequences of eruptions from U.S. volcanoes can extend far beyond the volcano’s immediate area. Many aspects of our daily life are vulnerable to volcano hazards, including air travel, regional power generation and transmission infrastructure, interstate transportatioVolcanoes!
Volcanoes is an interdisciplinary set of materials for grades 4-8. Through the story of the 1980 eruption of Mount St. Helens, students will answer fundamental questions about volcanoes: "What is a volcano?" "Where do volcanoes occur and why?" "What are the effects of volcanoes on the Earth system?" "What are the risks and the benefits of living near volcanoes?" "Can scientists forecast volcanic eAirborne volcanic ash; a global threat to aviation
The world's busy air traffic corridors pass over or downwind of hundreds of volcanoes capable of hazardous explosive eruptions. The risk to aviation from volcanic activity is significant - in the United States alone, aircraft carry about 300,000 passengers and hundreds of millions of dollars of cargo near active volcanoes each day. Costly disruption of flight operations in Europe and North AmericaEruptions in the Cascade Range during the past 4,000 years
Volcanoes have been erupting in the Cascade Range for over 500,000 years. During the past 4,000 years eruptions have occurred at an average rate of about 2 per century. This chart shows 13 volcanoes on a map of Washington, Oregon, and northern California and time lines for each showing the ages of their eruptions.Volcano hazards— A national threat
When the violent energy of a volcano is unleashed, the results are often catastrophic. The risks to life, property, and infrastructure from volcanoes are escalating as more and more people live, work, play, and travel in volcanic regions. Since 1980, 45 eruptions and 15 cases of notable volcanic unrest have occurred at 33 U.S. volcanoes. Lava flows, debris avalanches, and explosive blasts have invVolcano hazards in the Mount Hood region, Oregon
Mount Hood is a potentially active volcano close to rapidly growing communities and recreation areas. The most likely widespread and hazardous consequence of a future eruption will be for lahars (rapidly moving mudflows) to sweep down the entire length of the Sandy (including the Zigzag) and White River valleys. Lahars can be generated by hot volcanic flows that melt snow and ice or by landslidesLiving with volcanoes
The 1980 cataclysmic eruption of Mount St. Helens (Lipman and Mullineaux, 1981) in southwestern Washington ushered in a decade marked by more worldwide volcanic disasters and crises than any other in recorded history. Volcanoes killed more people (over 28,500) in the 1980's than during the 78 years following 1902 eruption of Mount Pelee (Martinique). Not surprisingly, volcanic phenomena and attend - News