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Trip to
Mount St. Helens, Washington
Even though this was mostly a “business” trip, we decided we had to make time to at least drive up to Mt. St. Helens, since we both really, really wanted to see it. We both graduated high school just weeks after the big eruption on May 18, 1980, so it was something we remembered very well; and Brad said it was a primary factor in his desire to study geology in college. I had been there to see it when I lived out there, but that was in 1991-92 – about 12 years after the eruption, and it is now another 12 years later, and I was eager to see the changes.
Well, as is so often the case in the Pacific Northwest, it was a bit rainy. The weather was beautiful the few
days before we got there, but as we flew in Friday evening (June 4th), there was a fairly solid cloud layer
building, though we thought we could see the summits of Mt. St. Helens and Mt. Rainier poking through as we came
in to land – and that was the last we saw of mountaintops for days. Saturday was really rainy. Sunday and Monday
were cloudy, with intermittent rain – but not enough to hinder us in loading up the truck. By Monday night, that
was done. We had been watching the weather forecasts and it looked like we might get lucky with some clearing of
the clouds on Tuesday – which was good, since we were out of time and had to start our drive back. But we could
spare half a day to go take a look at the volcano.
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The Mount St. Helens visitors Center is only a little over an hour’s drive from Portland – but it’s only about 5 miles off I-5, and not all that close to the mountain. I don’t know if you can see the volcano from there on a clear sunny day (they do have those – pretty much all of July and August, even late June, but any other time is iffy), but we sure couldn’t see it from there. We did see a 20-25 minute movie about the eruption and the aftermath that was pretty good, a bunch of exhibits, and stopped in the gift shop for postcards and souvenir ash. We’d planned to drive on to the Johnson Ridge Observatory -- as close as you can get by driving (this time of year) and really pretty darn close – but that was another hour-plus drive along Route 504, and while the clouds did seem to be showing signs of maybe breaking up, they sure weren’t gone yet at 10:30 or so when we were ready to leave the visitor’s center. But we decided to spend the time for the drive and hope. |
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Much of the drive is along the Toutle River, which is the one that bore the brunt of the onslaught of mud / debris from the landslide, the pyroclastic flow, and the draining of the displaced water from Spirit Lake. It’s not normally a very big river, and it was filled quite a bit beyond capacity sending a massive lahar (mudslide) down the watercourse, taking out the banks and bridges on its way down to the Columbia. The damage is still quite evident – though changing in interesting ways. You can see areas where 5-20 feet of newly-deposited (and so still fairly soft) mud / ash / whatever are eroding quite quickly – at least in geologic terms. What would take thousands or millions of years to erode from sandstone or shale has taken only 2-1/2 decades to be carved into those characteristic hills, valleys and runnels, hindered only slightly by the root systems of brush and young trees trying to get established. Parts of it looked to be well on the way to growing over, and other parts still looked like a moonscape. |
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When I saw it 12 years ago, there were still thousands of naked tree trunks lying just where the pyroclastic flow had blown them down, like tooth-picks dumped from their box but strangely oriented all in the same direction. Now those trees appear to have washed away – they were within the Volcanic Monument area, and so nothing has been removed by man (or added, except the road and observatories, no planting) – only the stumps are left, and the occasional washed-away and buried trunk being exposed again. Also, most of that eerie gray moonscape look is gone – even 12 years ago, it looked mostly gray with a bit of green starting to sneak in everywhere if you looked closer; now the green is dominating, with patches of gray showing through. |
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You can see from the pictures that while there was plenty of cloud left, there were also beginning to be good-sized patches of sky, and by the time we got to Johnson Ridge, parked, and walked up to the overlook, this is what we saw: |
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The valley below the blown-out north side of the crater shows again signs of rapid erosion of soft ash / mud deposits, which could be clearly seen between the cloud shadows chasing across the valley. And while Mt. St. Helens had a permanent snowcap before the eruption, there is now about 3000 feet less mountain, so this snow will likely all be melted by now. |
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The building at the Johnson Ridge Observatory is much smaller than the Visitor’s Center. Pretty much, it has a small gift shop, a few displays, and a lot of windows facing the view towards the crater – in case you want to look for breaks in the clouds without standing outside and getting drenched. One cool display was this stump of one of the trees that got blown down – takes a bit of force to knock over a tree that size. They also have a recording seismograph, listening to the current gurgles and grumbles the mountain still gives out. The lava dome still burps out another layer every now and then. Soon it will fill out that hollow crater – should only take a couple hundred years or so, and you’d never know anything had happened – unless you dug through the layers of sediment and deposition to try to piece together the volcano’s history. This eruption gave geologists a much better idea of what’s possible, and how to interpret such backward-looking deposit data. |
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