Earthquake Swarms on Mt. Hood Days Before 36th Anniversary of Mt. St. Helens Eruption

There are reports today of an earthquake swarm near the vents under Mt. Hood. These small earthquakes are somewhat common, but an exciting movement nonetheless. If you want to learn more about volcanoes, check out June's Ecology Club Night at Bark. It reminded us that Wednesday is the 36th anniversary of the eruption of Mt. St. Helens, another beloved volcano to the north. Bark's Restoration Coordinator, Russ Plaeger was there the day it erupted and wrote this memory of that day.

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Sunday, May 18, 1980 – Stevenson, WA. approx. 8:50 a.m.

Just after breakfast, I received a call from the Forest Supervisor’s office; the message was urgent and brief. “Come to work the mountain blew.” At the time I worked as the recreation program manager on the Wind River district of the Gifford Pinchot National Forest. We’d been watching Mount St. Helens erupt for the past few months and had been present when a convoy of Forest Service trucks and private cars “evacuated” the employees and families who lived at what was then the St. Helens Ranger Station. Due to frequent minor ash eruptions I had spare air filters in my orange VW Bug and a dust mask hanging on the mirror.

As I drove past the old WKO sawmill on the outskirts of Carson I had my first glimpse of the huge eruption column of ash to the northwest. This eruption was different. When I arrived at the ranger station at Hemlock in the Wind River valley there was a quick briefing on the situation; we were put in teams of two and sent out to check campgrounds, dispersed camp sites, and logging roads for people who were in the forest but perhaps unaware of the eruption. I gassed up my pickup, grabbed my fire pack and headed up the Wind River valley to Old Man Pass. Our assigned area was from Old Man Pass north to Lone Butte and east along the boundary of the Indian Heaven Wilderness Area.

When we arrived at Old Man Pass at approx. 10:15 we encountered a car full of scared people. They’d been camping down in the Lewis River valley, near the mountain, and made a quick escape soon after the eruption. Because they’d driven through a zone where a mix of rain and ash was falling their car was coated in gray and looked like it had been under a cement truck that was unloading. They were very happy when we told them to drive down the Wind River to a safe, unaffected area.

The lateral blast went to the north so we were safely out of reach of danger but had a spectacular view of the roiling, dark, ash filled clouds that filled the sky. We were about 18 miles from the volcano. As we drove FS road 65 we checked each of the trailheads for the Indian Heaven Wilderness. During one stop we stood watching the continuing eruption and noticed a fast-moving cloud of ash, in a glacier filled valley, on the east flank of the volcano. A week later while reading a USGS paper that had predicted an eruption much like the one that occurred I learned that the fast-moving cloud was probably a pyroclastic flow, a dense, hot (up to 1000 deg. C) mix of rocks, ash and gas that can travel up to 450 mph. In retrospect, I was very glad that flow stopped near the base of the volcano. I’d been in harm’s way during my summers as a wildland fire fighter but that Sunday was a completely different experience because the scale of the eruption was enormous.

My job changed that day and didn’t get back to normal until late summer. I was assigned to manage the volcano closure area and road blocks on the ranger district; every logger and FS employee who went into the forest had to check in and out daily so we knew where they were in case an evacuation was needed due to another eruption. My maintenance crew and summer recreation staff stopped preparing our campgrounds for the usual Memorial Day opening weekend; instead we set up a temporary information station at the, now defunct, log scaling ramp outside of Carson so we could direct people to campgrounds in the Mt. Hood area and Columbia River gorge. I equipped my trail crew with a stock of dust masks and extra air filters and chains for their saws so they could continue logging out the trees that had fallen across trails during the winter. And each of us had to sign what I recall was a waiver saying we accepted the health risks of working in areas where there was a dusting of ash on everything.

I thought about my St. Helens experience while writing the recreation section of Bark’s comments on the Environmental Assessment for the proposed Polallie-Cooper Timber Sale. People often talk about wildland fires as disasters that ruin the landscape and propose lots of logging to prevent a disaster. I think about fires and volcanic eruptions as natural processes that alter and rejuvenate the areas where they occur. In the case of Mount St. Helens the eruption created a fantastic living laboratory that has attracted scientists and a huge number of visitors to witness the natural recovery in the 36 years since “the mountain blew.” It would be great if we could take the long view and come to see fires and volcanoes as natural forces that have been shaping Northwest forests for many centuries.

 

Photo by Robert Krimmel/USGS