In the fog and pine-covered mountains of the Pacific Northwest, active volcanoes wait patiently above the ridgelines leaving residents on edge. Many fear the impending eruptions of the peaks. Washington state’s volcanoes are particularly dangerous with multiple considered to be at least high threats to volcanologists.
The famous and catastrophic eruption of Mount St. Helens in 1980 is still fresh for those who lived in the Pacific Northwest at the time. An estimated 2.3 billion cubic meters—a volume that would fill more than 900,000 Olympic-sized swimming pools—of ash, pumice, dirt, and rock flowed downslope resulting in the largest landslide in recorded history.
This debris flow continued to travel 14 miles west at up to 25 miles an hour using the North Fork Toutle River as its guide. It turned what was once a river of abundance into a river of concrete by uprooting trees, carrying car-sized boulders along its path, bulldozing 27 bridges, and devastating local communities and farms. Ash continued to pour from the volcano for hours.
While volcanoes are known for producing sinewy streams of lava and billowing plumes of ash, the St. Helens eruption underscored a lesser known but equally potent volcanic hazard: massive debris flows known as lahars. These slurries of water, sediment, and rocky debris originate atop a volcano and tumble rapidly downslope under gravity. The destruction St. Helens wrought had less to do with the eruption itself than the repercussions of the massive landslide it generated.
All told, the eruption and its aftermath took 57 lives and caused $860 million dollars of economic damage to roads, railways, communities, and the logging industry. That summer, the U.S. government established the Cascades Volcano Observatory (CVO) kicking off a gargantuan effort to monitor active volcanoes along the Cascade Range which stretches from Northern California to British Columbia and includes volcanoes like California’s Mount Shasta, Oregon’s Crater Lake, and Mount Rainier in Washington.
Researchers had a lot to learn about how to best communicate the risks of volcanic disasters and adequately prepare the public. Because it wasn’t a question of if another eruption would happen again; it was a matter of when.
Right now in Alaska, the state’s largest city is preparing for an eruption that has a 50 percent chance of happening.
But what is the largest volcano in Cascadia? Which Pacific Northwest volcano is most likely to erupt? When could these volcanoes erupt? The answers might surprise you.
When is the next volcanic eruption likely in the Pacific Northwest?
There are multiple volcanoes with a high or very high threat potential
In the Pacific Northwest, United States Geological Survey (USGS) researchers have called lahars “the most threatening hazard” in the Cascades, largely due to their direct access to communities. In the last 10,000 years, more than 60 lahars have originated from Mount Rainier which is situated about 50 miles northeast of St. Helens and looms large over the Seattle skyline. According to the USGS, 150,000 people in Pierce County live in Rainier’s projected lahar path.
A giant volcano in Alaska is showing signs of an impending eruption. Significantly elevated levels of volcanic gas emissions were recently observed around Mount Spurr which is located 75 miles from Anchorage and is home to nearly 300,000 people.
Geologists, seismologists, volcanologists, and residents in Anchorage have had their watchful eyes on Mount Spurr for the better part of a year after unprecedented seismic activity has heightened beyond the ‘norm’ causing unease and concerns that the mountainous volcano is inching closer to eruption each day.
Last month, the Alaska Volcano Observatory and the USGS stated they measured “significantly elevated volcanic activity with newly reactivated gas fissures or fumaroles seen at Mount Spurr’s Crater Peak.” That activity prompted a swift warning by both agencies and again on Wednesday, March 19th on the agency’s “X” page warning residents to be prepared for an imminent eruption.
As Alaska’s Mount Spurr stirs, shakes, rumbles, and continues to show obvious signs of awakening and erupting, residents are again being urged to brace for an eruption within the coming days, weeks, or months.
After a year-long period of continual and increasing seismic activity, scientists provided an estimated chance of Mount Spurr’s eruption last month at 50/50. Since last month, the Alaska volcano has shown telltale signs that there is a greater than 50 percent chance of eruption and when and if Mount Spurr should erupt, it will be the first major eruption since 1982. That eruption’s plume from its first explosion reached 47,500 feet and its second explosion closed the Anchorage airport for 20 hours.
Small earthquakes were detected at Mount Rainier, Mount St. Helens, and Mount Hood during the past month. These are the Cascade Range. We did have the Volcan de Fuego or Volcano of Fire blowing a thick ash cloud seen from Palin, Guatemala on Monday, March 10, 2025. This is more of a concern. Numerous volcanoes can have an accumulative effect.
Scientists have their eyes on the Cascade Range, a 1,200-mile stretch of volcanoes that form a trail of peaks from British Columbia to northern California.
The Washington portion of this range is especially active and has seen recent eruptions even after the aforementioned 1980 catastrophe. From 2004 to 2008, Mount St. Helens once again erupted though it was a more gradual process than the previous explosion.
There are currently five volcanoes in the Pacific Northwest that are deemed as high or very high threats:
Mount Spurr
- Location: Kenai Peninsula Borough, Alaska
- Elevation: 11,070 feet
- Last erupted: 1992
Mount Baker
- Location: Whatcom County, Washington
- Elevation: 10,781 feet
- Last erupted: 1843
Mount Rainier
- Location: Pierce and Lewis counties, Washington
- Elevation: 14,410 feet
- Last erupted: 1450
Mount St. Helens
- Location: Skamania County, Washington
- Elevation: 8.300 feet
- Last erupted: 2004-2008
Mount Adams
- Location: Skamania, Yakima, Klickitat, and Lewis counties; Washington
- Elevation: 12,276 feet
- Last erupted: 1800 BC–5600 BC
More dangerous volcanoes you need to know about
These volcanoes pose a threat
Alaska contains about 140 volcanoes and volcanic fields active within the last 2.6 million years (the Quaternary).
About 90 of these volcanoes have been active within the last 11,000 years (the Holocene) and more than 50 have been very recently active within the last 300 years or so.
The volcanoes in Alaska make up more than three-quarters of US volcanoes that have erupted in the past 200 years.
Most of Alaska’s volcanoes are located along the 1,500 mile Aleutian Arc which extends westward from the mainland of Alaska towards Kamchatka and forms the northern portion of the Pacific “ring of fire.” Other volcanoes in Alaska that have been active in the last few thousand years exist in southeastern Alaska (Edgecumbe) and the Wrangell mountains. Smaller volcanoes, some active within the past 11,000 years, are found in interior Alaska and in western Alaska as far north as the Seward Peninsula.
Other volcanoes along the Pacific Rim from Alaska to California of note include:
Mount Redoubt
- Location: Kenai Peninsula Borough, Alaska
- Elevation: 10,197 feet
- Last erupted: 2009
Akutan Peak
- Location: Akutan Island, Aleutian Islands, Alaska
- Elevation: 4,279 feet
- Last erupted: 1992
Makushin Volcano
- Location: Unalaska Island, Aleutian Islands, Alaska
- Elevation: 6,680 feet
- Last erupted: 1995
Mount Meager
- Location: Lillooet Land District, British Columbia
- Elevation: 8,790 feet
- Last erupted: 410 BC ± 200 years
Mount Garibaldi
- Location: New Westminister Land District, British Columbia
- Elevation: 8,786 feet
- Last erupted: 8060 BC ± 500 years
Glacier Peak
- Location: Snohomish County, Washington
- Elevation: 10,541 feet
- Last erupted: 1700
Mount Hood
- Location: Clackamas and Hood River counties, Oregon
- Elevation: 11,249 feet
- Last erupted: 1865-1866
Crater Lake
- Location: Klamath County, Oregon
- Elevation: 6,178 feet
- Last erupted: 5700 BC
Mount Shasta
- Location: Siskiyou County, California
- Elevation: 14.179 feet
- Last erupted: 1250
Lassen Peak
- Location: Shasta County, California
- Elevation: 10,457 feet
- Last erupted: 1914-1921
How can you tell when a volcano will erupt?
Most volcanoes provide warnings before an eruption
As volcanoes don’t tend to erupt at timed intervals—for example, every ten years—it can be quite a task for volcanologists to predict when the next volcanic eruption will happen in the Pacific Northwest.
However, scientists state that a volcano could erupt any time particularly in Alaska and Washington State where most of the highest-threat volcanoes are on the West Coast. These sites are looming disasters and beloved recreation areas in the Pacific Northwest. Residents and visitors to the state flock to the towering peaks for scenic hikes, award-winning ski slopes, camping, hiking, mountain biking, and more.
This is not just the case for Washington and Oregon volcanoes. Around the world, the rise of dark tourism is leading to skyrocketing volcano visitor numbers including at Indonesia’s blue lava spectacle. Meanwhile, at Hawaii Volcanoes National Park tourists are flocking to Kīlauea as it erupts and lava spews many feet up in the air.
Note: Volcanoes are considered the most striking evidence of plate tectonics offering visitors a glimpse of a largely invisible process. These peaks are among the few spots where molten rock emerges on the surface.
What would happen if a volcano erupted in the Pacific Northwest?
From lahars to smoke clouds, the effects would be catastrophic
Though volcanic eruptions in the Pacific Northwest aren’t very frequent, they are incredibly violent when they do happen. During an eruption, volcanoes send gas, rock, and ash high into the air making breathing hard and killing swaths of nearby wildlife. This blast leads to volcanic glass, more ash, and minerals going airborne and firm what’s called an eruption column cloud.
One of the world’s most active volcanoes produced ash clouds that were over two miles high. Meanwhile, any large debris that falls from the sky is called volcanic bombs as they damage anything within a few miles of the vent. Together, these results of the initial eruption are called tephra and they can not only damage communities below but also airplanes in the sky if they fly through the cloud. All of this can also put locals at risk of lung damage.
If the blast is strong enough or in the case of volcanic collapse, this can cause a pyroclastic flow or a rapidly moving mix of gas, rock, and ash that spills over the cone and down the slope at top speed—they can reach 100-150 miles per hour. Between the speed and the temperatures that hit over 1,500°F the pyroclastic flow flattens and kills everything it goes near.
After the eruption’s blast and tephra, lava then emerges. As it gets on the move, it destroys everything in its way. Lava with low viscosity (meaning it’s not sticky) like basalt moves quickly and can reach further distances while high viscosity (meaning it’s sticky) lava like rhyolite moves slower and less far. The heat emitted from either melts snow and ice that aren’t directly in the path but are nearby which leads to the most dangerous part of all: lahars.
These are hazardous flows of debris and mud. While the eruption, lava, and ash devastate all infrastructure within ten miles of the eruption, lahars destroy anything within 50 miles and if it’s a low-lying area, it can be even further away and still be a casualty. In Washington State, lahars are known to travel up to 120 miles per hour and some have so much solid material in them like rocks that it looks like a superspeed train of concrete.
Lahars are the deadliest part of a volcanic eruption and if there was another one in the Pacific Northwest, it would be the costliest hazard of all. This is not just due to their force, speed, and reach but also because they can happen at any time. Lahars don’t need a volcanic eruption to occur and can happen during intense rainstorms.
While Seattle would most likely just be at risk of ash, cities in the foothills like Puyallup and Orting would be devastated by all volcanic hazards especially lahars. For this reason, citizens regularly participate in lahar evacuation drills.
Note: The eruption of Mount St. Helens in 1980 blanketed 22,000 square miles with ash. Despite this seemingly large mileage it was considered a relatively modest eruption as far as size goes. Bigger eruptions like that of the South Pacific’s Krakatoa in 1883 produce enough ash to lower the entire planet’s temperature for years.
How to know if a volcanic eruption is imminent in the Pacific Northwest
It’s all about staying informed and practicing ahead of time
Although it can be tricky to pinpoint the exact moment when a volcano will erupt, there are some clues that experts rely on. Eruptions are often paired with earthquakes as the magma in the volcano makes its way up through the cone and to the surface. Although earthquakes aren’t a sure sign of an upcoming eruption even if it’s a “swarm” of them, if they happen alongside gas emission, temperature changes, and deformation events this hints strongly that the volcano will erupt.
For this reason, volcano seismologists track earthquakes and seismic signals that suggest magma is moving. The CVO posts a weekly volcanic activity update in the Pacific Northwest. The big five volcanoes in Washington are detailed as well as Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake in Oregon.
Data is compiled in partnership with the University of Washington Pacific Northwest Seismic Network which publishes a map of volcanic activity accessible to all. Viewing resources like these regularly is a great way to prepare for eruptions in the Pacific Northwest.
Learning about the risks you face in your neck of the Pacific Northwest is key. Even if you’re a visitor to the area, it’s still advised that you understand the volcanic updates before coming. Those living in places like Iceland which is being deemed the volcano capital of the world live by emergency preparedness.
How to prepare for a volcanic eruption in the Pacific Northwest
Have water, food, and emergency supplies ready and stored safely
Having a go-to bag is critical. Every person’s go bag will look different. And it should be easy to carry and maintain.
Consider making an emergency go-bag checklist so you don’t forget anything necessary. Staying updated with your local weather stations and national services is also a great way to be informed and prepared. Note any evolving situations and adapt your packed items accordingly.
Essential items include goggles, breathing masks, essential contact information, important documents.
Plan an evacuation route for both landslides and lahars, prepping a path that directs you and your loved ones away from streams, river valleys, and anywhere that’s low-lying.
Listen to All Hazard Alert Broadcast sirens and local news stations for warnings and evacuation orders.
Subscribe to volcano notification services.
If an eruption does happen but you can’t evacuate, get to high ground and stay inside, closing all windows, doors, and vents until ash stops falling. If possible, head to a designated evacuation area or public shelter once the eruption is over.
While the lush, mountain-speckled landscapes of the Pacific Northwest offer plenty of beauty, they also offer potential danger. However, if you’re informed and prepared, there isn’t any reason why you can’t enjoy and get lost in the scenic wonderland.
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- See Steaming Volcanoes at This Eerie National Park
- Celebrate Volcano Week!
- Mount St. Helens: On the Eruption 40 Years Ago & Future Eruptions
Worth Pondering…
Each volcano is an independent machine—nay, each vent and monticule is for the time being engaged in its own peculiar business, cooking as it were its special dish which in due time is to be separately served. We have instances of vents within hailing distance of each other pouring out totally different kinds of lava, neither sympathizing with the other in any discernible manner nor influencing other in any appreciable degree.
—Clarence Edward Dutton, Report on the Geology of the High Plateaus of Utah (1880)
