Does Portland, Oregon have a volcano within its metropolitan area?

Like Auckland, New Zealand, the town of Portland, Oregon has most of a Plio-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.


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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...

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...

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...

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 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 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 19th, 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...

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...

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,...

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...

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...
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Date published: September 12, 2016


It’s not flirting for submarines, but this week’s EarthWord does feature the ocean...

Date published: August 22, 2016


Look! In the sky! It’s a bird, it’s a plane! Wait, run, it’s this week’s EarthWord!

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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
three dimensional conceptual drawing of a tectonic plate being pushed down under another plate.
March 6, 2017

Cascadia Subduction Zone

Block diagram illustrating an idealized geological setting offshore the state of Washington. As the subducting Juan De Fuca tectonic plate dives beneath North America, it can generate an earthquake, and trigger a tsunami.

Image shows a diagram of a subduction zone
July 18, 2016

Subduction Fault Zone Diagram

A figure showing the oceanic plate sliding beneath the continental plate. Credit: USGS

snow-capped volcano, Mount Hood on the horizon, with city of Portland, Oregon in foreground
December 31, 2012

Mount Hood and Portland, Oregon

Mount Hood in the not-so-far distance beyond downtown Portland, Oregon. Photograph taken at the top of the Portland Aerial Tram line on Marquam Hill.

Mount Hood with Portland, Oregon in the foreground.
May 23, 2012

Mount Hood dominates the skyline outside of Portland, Oregon

A major eruption of Mount Hood would pose a great hazard to the regional economy.

muddy Willamette River
December 15, 2010

Willamette River through downtown Portland, OR

Photograph of the Willamette River passing through downtown Portland, OR.

June 23, 2009

What is tuff?

Listen to hear the answer.

Image: Cinder Cones on Mauna Kea
February 16, 1991

Cinder Cones on Mauna Kea

Cinder cones at the summit of Mauna Kea. Mauna Kea is a dormant shield volcano on the north end of Hawaii Island. Astronomical observatories in the foreground.

Cinder cones (otherwise known as scoria cones) are the most common type of volcano on Earth. They’re also one of the smallest. They can often be found growing on larger volcanoes, in which case they’re dubbed