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 without an eruption. However, all existing Boring Volcanic centers are extinct and the probability of an eruption in the Portland/Vancouver metro area is very low.
Learn more: USGS Cascades Volcano Observatory
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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...
Are there earthquakes associated with Mount Hood?
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...
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...
How can we tell when a volcano will erupt?
Most volcanoes provide warnings before an eruption. Magmatic eruptions involve the rise of magma toward the surface, which normally generates detectable earthquakes. It can also deform the ground surface and cause anomalous heat flow or changes in the temperature and chemistry of the groundwater and spring waters. Steam-blast eruptions, however, can occur with little or no warning as superheated...
Is it dangerous to work on volcanoes? What precautions do scientists take?
Volcanoes are inherently beautiful places where forces of nature combine to produce awesome events and spectacular landscapes. For volcanologists, they're FUN to work on! Safety is, however, always the primary concern because volcanoes can be dangerous places. USGS scientists try hard to understand the risk inherent in any situation, then train and equip themselves with the tools and support...
Why is it important to monitor volcanoes?
There are 161 potentially active volcanoes in the United States. According to a 2018 USGS assessment, 57 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 are increasing. As a result, more...
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 2004-2008. 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 through the middle of 1917. Mount Hood, Oregon -...
Related Content
- FAQ
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...
Are there earthquakes associated with Mount Hood?
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...
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...
How can we tell when a volcano will erupt?
Most volcanoes provide warnings before an eruption. Magmatic eruptions involve the rise of magma toward the surface, which normally generates detectable earthquakes. It can also deform the ground surface and cause anomalous heat flow or changes in the temperature and chemistry of the groundwater and spring waters. Steam-blast eruptions, however, can occur with little or no warning as superheated...
Is it dangerous to work on volcanoes? What precautions do scientists take?
Volcanoes are inherently beautiful places where forces of nature combine to produce awesome events and spectacular landscapes. For volcanologists, they're FUN to work on! Safety is, however, always the primary concern because volcanoes can be dangerous places. USGS scientists try hard to understand the risk inherent in any situation, then train and equip themselves with the tools and support...
Why is it important to monitor volcanoes?
There are 161 potentially active volcanoes in the United States. According to a 2018 USGS assessment, 57 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 are increasing. As a result, more...
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 2004-2008. 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 through the middle of 1917. Mount Hood, Oregon -...
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