Thursday, August 23, 2007

The Trip - Mt. St. Helens

We left the Seattle area Tuesday under a thick layer of clouds. In Olympia, we started seeing tiny slivers of blue sky, but they were short-lived. By the time we got to Chehalis, a blue circle had opened up in the sky, like the top of a Catholic monk's head crowned by a wreath of billowy white hair. It stayed with us for most of the day, changing shape once in a while.

Some of the trees in Washington have already started changing colors, and I'm concerned that autumn might come early this year, with our luck while we're stopping at home for a few weeks in early September.


When we leave for our Northeastern loop, we'll probably hurry to New Brunswick, Canada, for the world's longest covered bridge (hopefully before snowfall), and then make our way leisurely southward. If we're lucky, we should see autumn leaves somewhere along the way. But that's later. We're still in the West.

Near Mt. St. Helens there are three visitor centers, the first run by the state of Washington, and the other two run by the US Forest Service. We got to the first one late Tuesday afternoon in time to watch the movie about the 1980 eruption. I learned a lot that I hadn't known.

Beginning March 20, 1980, when the mountain "woke up," it built a bulge on the northern face, accompanied by hundreds of earthquakes. On May 18, 1980--a Sunday--at 8:32am, a 5.1 earthquake sent the bulging northern face tumbling down in a landslide. Without its support, more of the northern slope followed. The landslide, with the snow that had rested on that land, followed the course of the North Fork of the Toutle River, sending rock and mud through the valleys.

The loss of the mountainside gave the underlying magma an enormous weak spot, and it exploded laterally, sending rock and ash and gases over 270 square miles and as far as 17 miles away, and a cloud of ash 80,000 feet in the air. Pyroclastic flows contined throughout the day as the cloud of ash made its way eastward, reaching Spokane around 2:00 in the afternoon.

When the day was over, the blast had left debris from the top of Mt. St. Helens 230 feet deep where the landslide and the blast had settled. The debris formed dams that created two new lakes, Castle Lake and Coldwater Lake, both now 27 years old. Here is a picture of the mountain (hidden inside an unseasonal cloud, center) and the remains of the 1980 eruption (beyond the near ridge).


Wednesday we went to the Coldwater and Johnston visitor centers. At Coldwater we attended a ranger talk about the regrowth of the area.

In the picture just above, you can barely see the stumps of trees on the left side of the near (green) ridge. Those stumps were already there when the mountain blew. The area around Mt. St. Helens was Forest Service land, managed in a checkerboard pattern, with one square having been logged in a clearcut and the square next to it unlogged. Because the eruption happened in May, when there was still some snow on the ground under the unlogged trees, the recovery has progressed differently for the two types of land.

The explosion's force, debris, and incredibly hot gases flowed over the ridges the way water flows over rocks and sandbars in a river bottom. In the clearcut areas, the blast destroyed everything. In the unlogged areas, where there was still snow under the trees, the blast burned and knocked over the standing trees, but the snow protected the shade-tolerant undergrowth. The trees of the protected undergrowth, now exposed to the sunlight, have thrived in a way they couldn't before the blast. Biologists have been surprised by the speed of their recovery.

In the clearcut areas, primary regrowth is happening. Grasses and wildflowers took root first, and insects came in, inviting rodents, inviting birds of prey. The meadows have also brought elk, and recently, larger predators--bears and lions--have returned.

At the same time, all the new water--not just the two new lakes, but the new ponds formed in the depressions left by the blasts of rocks from the mountain--invited grasses and cattails, inviting amphibians that multiplied without predators for a time. The ranger said that the biodiversity around the mountain is greater now than it was before the eruption.

He also said the recovery started in the water and has been gradually moving out from there. In the photo above, the top of the near ridge is the only part that still doesn't have trees, but they should come soon.

A better example is the delta of Coldwater Lake. In the drawing on this sign, the delta was mostly barren (see green arrow).


But now, the delta is completely tree-covered. I believe he said the sign was made six years ago.


Mt. St. Helens is busy rebuilding itself again, as it does each time it erupts. The previous eruption was in the 1800s, so all the "Before" pictures are really the rebuilt mountain after the last time. The rebuilding and regrowth by nature may be new to modern observers, but it's as old as nature itself.

My mom and I drove beyond Coldwater to the Johnston visitor center, hoping the cloud would lift and give us a good view. But the cloud settled down even more, so I went with the flow and photographed the rolling mists. Here is a downed tree by the walkway.


And a trail that may be tough to follow.

2 comments:

Delta said...

Skye!

You said my name! (delta)

I feel so special...LOL

Thanks for sharing your trip and the beautiful photos.

SkyePuppy said...

Delta,

We aim to please!