AMU Emergency Management Public Safety

Mount St. Helens Tremors Bring Renewed Focus to Volcano Danger in PNW

Mt. Rainier, Mt. Hood, Mt. Baker, other peaks have high threat potential

U.S. Geological Survey (USGS) scientists reported earlier this month that more than 100 small earthquakes have shaken beneath infamous Mount St. Helens in southern Washington State since mid-March. While scientists do not believe that the group of seismic events introduces any immediate danger to the Pacific Northwest (PNW), the weeks long shaking is bringing a renewed focus to the volcano danger that looms in the region.

In scientific terms, a small-magnitude earthquake swarm struck underneath Mount St. Helens from March 14 to May 5, 2016. All told, 130 small earthquakes ranging from magnitude-0.5 to magnitude-1.3 at depths ranging from 1.2 to 4 miles occurred under the peak in that time period.

Despite the fact that the quakes were all too small to be felt at the surface, the swarm has received considerable media coverage since the [link url=”” title=”USGS reported the group of seismic events on May 5.“] Some are wondering if the coverage is warranted. Given the relatively low magnitude of this recent earthquake swarm, EDM Digest’s own John Pennington questioned, [link url=”” title=”should we care?“]

Larger threats loom

Mount St. Helens forever holds its place in U.S. history texts after its [link url=”” title=”massive 1980 eruption,”] but, according to the USGS’ Cascades Volcano Observatory (CVO), is just one of nine peaks in Washington and Oregon that are considered to have [link url=”” title=”high to very high threat potential“] of significant volcanic activity.

In Washington state, Mount St. Helens is joined by Mount Rainier, Mount Baker and Glacier Peak on the USGS’ “highest priority” list. Washington’s Mount Adams is just one notch lower, listed at “high priority.”

Mount Rainier is the highest peak in the Cascade Range, and one of the tallest peaks in the contiguous U.S., at 14,410 ft. It sits as a massive backdrop to millions of residents of Seattle, Tacoma and other neighboring cities and towns. Because of Mount Rainier’s sheer size and its proximity to major populations, the USGS consistently calls “The Mountain,” as it is referred to by Seattle-region locals, [link url=”” title=”one of our nation’s most dangerous volcanoes“].

In Oregon, Crater Lake, Mount Hood, Newberry, and Three Sisters are all listed as “highest priority” by the USGS, and there are also two peaks of high interest in Northern California, not far from the California-Oregon border, Mount Shasta and Lassen Peak.

Putting the recent Mount St. Helens earthquake swarm in perspective

USGS scientists called the March-May events at Mount St. Helens “volcano-tectonic in nature” and clarified the activity as “indicative of a slip on a small fault.” In non-scientific terms, the activity likely indicates that magma is moving around under the mountain, and that its system is recharging.

So, there are no signs of clear and immediate danger, no signs of a forthcoming eruption, but there are some signs that maybe Cascade volcanoes deserve a little more attention as possible threats as years pass by and populations grow in the PNW.

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Matt Mills has been involved in various aspects of online media, both on the editorial side and on the technology side, for more than 16 years. He holds a Master's Degree in Journalism from Northwestern University's Medill School of Journalism, and is currently involved in multiple projects focused on innovation journalism.

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