BURLINGTON, Wash. – Ever since steam was spotted rising from Mount Baker two decades ago, the volcano has been a focus of geologists in the North Cascades.
When Mount Baker erupts, crumbles or both, the Skagit Valley may be in trouble, geologist Dave Tucker said. But the extent of the damage will depend on many factors, including which side of the mountain gives way and which way the wind is blowing.
“We’re definitely in the hazard zone here,” he said Thursday at Burlington Public Library during an event about the risks of living in Mount Baker’s shadow.
Geologists say Mount Baker is the second most active volcano in the mountain range behind Mount St. Helens.
An eruption or slide at Mount Baker could crush the Baker River dams, destroy roads and utility systems, and flood land along the Skagit River from Rockport west, according to the U.S. Geological Survey. It could take decades to repair the damage.
That’s the worst-case scenario, said Tucker, who founded the Mount Baker Volcano Research Center.
The scenario assumes a landslide – called a lahar when associated with volcanic activity – from the southeast flank of Mount Baker would spill into Baker Lake and the Baker River north of Concrete, cause dams to fail and send debris and floodwater rushing downstream.
While that outcome is not a pretty picture, experts say the risks are slight compared to the damage a magnitude-9 earthquake could inflict on the region.
“A big magnitude-9 earthquake is going to cause a lot more problems here than an eruption at Mount Baker,” Tucker said.
Geologists say the Cascadia fault – a subduction zone in the ocean along the West Coast – could unleash a major earthquake anytime.
Tucker said there is no known correlation between earthquakes and volcanic eruptions, which means it’s not likely a Cascadia earthquake and a Mount Baker eruption would occur at the same time.
When Mount Baker blows
According to the USGS, at-risk communities likely will be warned days or even weeks before an eruption.
Eruptions are often preceded by a series of earthquakes. The Pacific Northwest Seismic Network monitors movement at Mount Baker with two seismometers that can detect shaking even if nearby residents don’t feel it.
The nonprofit Mount Baker Volcano Research Center also sends volunteers to Sherman Crater on the south side of the volcano once a year, where they collect samples of the gases rising from the rock.
“That gives a possible long-range warning of changes within the volcano,” Tucker said.
Since a dark gaseous cloud drew attention to the crater in 1975, the release of heat and gas has not simmered down, he said.
Changes in the makeup or temperature of gases coming from the volcano, as well as earthquakes or other changes to the rock surface, are key indicators a volcano is likely to erupt, according to the USGS.
When an eruption does happen, it’s not likely to send a lot of material toward Skagit County unless accompanied by a lahar.
Mount Baker is known to produce thick, rocky lava that doesn’t move very fast or get very far, Tucker said.
Ash is likely to cause more trouble following an eruption, since it can damage engines such as those that run cars and electric systems.
How much ash reaches local communities will depend on the day’s weather. USGS models suggest the wind could carry ash as far as Northern California, into the Midwest or into Canada.
The only evidence of ash previously being left in Skagit County is about an inch found in Marblemount, Tucker said. That suggests the wind was blowing east at the time, and the eruption was smaller than Mount St. Helens’ most recent blast in 1980.
Not the only
Mount Baker isn’t the only active volcano looming over the Skagit Valley.
The lesser-known Glacier Peak to the south is believed to have had some of the largest, most explosive eruptions in the U.S., according to the USGS.
Both volcanoes are considered high to very high threats, according to the USGS.
Like Mount Baker, Glacier Peak lahars pose big risks.
Streams flow from Glacier Peak into the Sauk and Skagit rivers – a route lahars are likely to follow as well, according to USGS. About 13,000 years ago, lahars tumbled down the Suiattle, Sauk, Skagit and Stilliguamish rivers, leaving a trail of sediment up to 7 feet deep.
The Skagit County Department of Emergency Management equates that to an eruption 10 times the size of the 1980 one at Mount St. Helens.
Skagit, Whatcom and Snohomish counties have partnered with state, federal and Canadian government agencies to develop the Mount Baker-Glacier Peak Coordination Plan.
The plan lays out the responsibilities of each agency, along with procedures for warning and evacuating the public following signs of volcanic activity.
What’s at risk?
With Mount Baker in Whatcom County and Glacier Peak in Snohomish County, Skagit County is nestled between two active volcanoes. Concrete in particular lies in the potential hazard area for both volcanoes.
Lahars from either volcano could cover the southeastern portion of the town, according to the USGS.
Mount Baker lahars could send debris and floodwater along the Skagit River, inundating most of state Route 20, Hamilton, Lyman, Sedro-Woolley, Burlington, parts of Mount Vernon and areas as far northwest as Samish Island and as far southwest as La Conner and Conway, according to the USGS.
Twenty-eight schools in Skagit County lie in the potential path of Mount Baker or Glacier Peak lahars, according to the 2012 Washington State K-12 Facilities Hazard Mitigation Plan.
“Lahars are the primary threat and present the greatest hazard to Skagit County resulting from volcanic activity at either Mount Baker or Glacier Peak … They can travel more than 60 miles downstream, commonly reaching speeds between 20 and 35 mph,” according to the Skagit County Natural Hazards Mitigation Plan.
Though thousands of years tend to pass between major eruptions, both Mount Baker and Glacier Peak have the potential to wreak havoc on Skagit County, according to the plan.
The steam rising from Mount Baker today signifies the volcano will erupt eventually, Tucker said.
Evidence of an eruption about 6,600 years ago indicates a 280-foot-thick lahar swept over the Nooksack River, which was forced to take on a new route.