It is difficult to predict when a volcano such as Mount Baker or Glacier Peak will erupt.
How it will erupt – spreading lava, spewing ash, blowing mountain tops – and how long the effects will last are even harder to calculate.
While experts said Friday during a talk in Concrete that communities near those volcanoes shouldn’t despair, residents should be aware of the sleeping giants in their backyard and have a plan in case they wake.
“Just keep all of the ‘What if’s’ in the back of your mind,” said Cynthia Gardner of the U.S. Geological Survey’s Cascades Volcano Observatory.
While Mount Baker is in central Whatcom County and Glacier Peak is in east Snohomish County, Skagit County is not in the clear.
“You don’t have any of the volcanoes here, but you could get all the impacts from both of them,” said Brian Terbush, volcano program coordinator with the state Emergency Management Division.
Past eruptions from both volcanoes have left their marks – layers of ash and other volcanic debris unearthed by geologists – in Skagit County.
And while neither nearby volcano has had a major eruption in thousands of years, they remain active and could erupt at any time.
“They will certainly erupt again,” Gardner said. “The bad part is that we can’t tell you when that will be.”
An eruption could be deadly, primarily due to lahars, which are volcanic landslides that may be mixed with water, snow and ice.
Terbush said that’s why it’s important for those living near Mount Baker and Glacier Peak to be aware that they are active volcanoes, to have a plan in case they erupt and to stay up to date with what’s happening at the volcanoes.
If there’s a volcano warning, Terbush and Gardner said not to ignore closures in the Mount Baker-Snoqualmie National Forest and North Cascades National Park and to follow evacuation recommendations.
“You cannot shelter in place,” Gardner said.
The devastation of lahars has been seen in other parts of the world. In the community of Armero, Colombia, 23,000 were killed by a lahar from the volcano Nevado del Ruiz in 1985.
“Most of those people could have gone a quarter-mile or a half-mile away and survived,” Gardner said. “That’s something that has haunted the volcanologist community. We don’t want that to happen anywhere in the world, but especially not here at home.”
Here, lahars from Mount Baker and Glacier Peak have the potential to reach several miles from the volcanoes and send floodwater even farther.
In the event of a major eruption, debris or flooding could reach the lower Skagit River valley, according to the USGS.
In the case of Mount Baker, Concrete is the first Skagit County community in danger. For Glacier Peak, it’s Rockport.
Another concern with a major eruption from Mount Baker is the potential for a lahar to break through the Baker River dams and set loose a major flood, which Skagit County Department of Emergency Management’s Vickie Fontaine said could hit Concrete within minutes.
Gardner said an eruption could impact communities throughout the Skagit Valley for years, with volcanic sediment displacing river water and resulting in flooding.
“Even if you aren’t affected by the original lahar, you could be affected years, decades later by the sediment coming down the river valley,” she said.
At this time, neither Mount Baker nor Glacier Peak is showing signs of what geologists call “unrest,” which is an indication an eruption may be coming, according to the USGS.
Volcanoes show unrest through increased earthquake activity, increased releases of gas or changes in shape, such as bulging that was noted before Mount St. Helens erupted in 1980.
The history and current activity of volcanoes are important for geologists and emergency responders, who use that information to inform and warn the public of potential eruptions or lahars.
The USGS monitors volcanoes including Mount Baker and Glacier Peak with a variety of tools, including some that can sense earthquakes or changes in gases in the air.
Those changes, or signs of unrest, are expected to emerge weeks to months before an eruption occurs, Gardner said.
Volcanoes sometimes erupt from the buildup of pressure far below the Earth’s surface.
The largest Mount Baker eruption geologists have found evidence of happened about 7,000 years ago, Gardner said. It was about one-fifth the size of the well-known eruption at Mount St. Helens, but was powerful enough that it sent lahars into the Nooksack and Baker rivers.
“That would be quite destructive and affect us regionally if it were to happen again,” Gardner said.
The largest known eruption from Glacier Peak was about 13,000 years ago. Gardner said it left about 2.5 feet of ash in some places and sent lahars several miles.
While there has been some activity at Mount Baker and Glacier Peak since their last eruptions, including an increased release of gases at Mount Baker in 1975, neither volcano has major eruptions very often.
“The likelihood of an eruption during our lifetimes is really low, but the consequences … could really affect a broad area,” Gardner said.