Dangerous Glacier Peak Volcano minimally monitored

Glacier Peak is the second-most dangerous volcano in the Cascades, after Mount St. Helens, and yet it has only three seismic monitoring stations.

Glacier Peak is the forgotten volcano

Called Tda-ko-buh-ba by a tribe of American Indians who have lived on its flanks for hundreds of years, it erupts more explosively than any volcano in Washington, including Mount St. Helens.

Glacier Peak is one of 18 volcanoes in the U.S. listed as a “very high threat.” It made the list because its historical record shows it erupts frequently and on a large scale.

Glacier Peak (click or tap image to enlarge)

It last erupted about 240 years ago, just before the Revolutionary War, and its last major eruption was about 1,800 years ago. Of the volcanoes on that list, Glacier Peak, at 10,541 feet, is among those with the fewest seismic monitoring stations.

Even so, volcanic experts believe they have enough seismometers that watch for clusters of earthquake activity to know when an eruption could be imminent. Also, a reverse 911 calling system would allow thousands of people to be notified within minutes.

Only in 2007 did Snohomish County begin requiring landowners to sign a document that, for the first time, makes them acknowledge that they’re buying or building a home within the long reach of Glacier Peak.

St. Helens, Rainier, and, to a lesser extent, Baker are dotted with seismometers. Continuous Global Positioning System monitors are ready to catch even the tiniest movements at the top of those volcanoes. Glacier Peak has only three seismometers and no GPS monitoring stations.

John Ewert, scientist-in-charge at the U.S. Geological Survey’s Cascades Volcano Observatory in Vancouver, Wash. says, “Right now, Glacier Peak is a volcano that we consider to be a very high threat volcano, it is at the present time the least well-monitored of all the Cascade volcanoes.”

Glacier Peak Lahar (click or tap image to enlarge)

Glacier Peak is 10,541 feet high and located southeast of Darrington in the Cascade Mountains, just inside the far eastern edge of Snohomish County. Because it’s tucked behind other mountains, it’s not as visible or as well-known as other nearby peaks.

Glacier Peak has had some huge eruptions in its history, sending walls of mud, rocks, trees and melted glacier water roaring down the Stillaguamish and Skagit valleys, obliterating everything in their path. Darrington is built on the remnants of several of these lahars, as the flows are called. Glacier Peak also has exploded fairly frequently compared to other Cascade volcanoes, Ewert said.

Glacier Peak tends to erupt explosively, and when the volcano reawakens the most serious hazards will impact population centers located relatively far away from the volcano. The mountain is within a wilderness area, and although it is isolated, areas downwind and downstream would be impacted by tephra, pyroclastic flows, and lahars.

Towns of Darrington, Rockport, Concrete, Sedro Woolley, Burlington, Mount Vernon, and La Conner lie in the Sauk and Skagit river valleys, which have been inundated by lahars in the geologically recent past. Winds over Glacier Peak are usually directed to the east; therefore airborne tephra may travel over much of the United States and Canada. Towns to the east, such as Winthrop, Twisp, and the Methow River valley are most likely to receive tephra fall, but if a very large eruption occurs ash fall will be broadly regional, and international, in scope.

Glacier Peak is a small stratovolcano in the Cascade Range of Washington. There are over one dozen glaciers on the sides of this volcano. Most of the loose pyroclastic deposits have been eroded by these glaciers. The tops of the ridges to the northeast of the volcano are covered by lava flows. Small basaltic flows and cones can be found around the sides of Glacier Peak. Lava flows only extend a few km from the top of the volcano.

Three hot springs flow from the ground around the volcano. Fresh looking dacite domes are positioned high on the north and south sides of the volcano. Warm ground and areas without snow surround these domes. Large fans of pyroclastic materials almost entirely fill the valleys on the east and west sides of the volcano.



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