Monday, September 19, 2011

Mount St. Helens Crater: At the Glacier (Part 2)

How can this frog...or anything...grow and thrive inside the crater of a volcano??

Mount St. Helens erupted and wiped out every living thing for 230 square miles on May 18, 1980. In the 30+ years since then, what was once a sterile volcanic debris field is gradually transforming.

The first plants to arrive were nitrogen-fixing plants like lupines, because they didn't need to have nutrients in the soil.
 The flower in the foreground of this photo is Indian paintbrush, but the silvery plant in the background is the diminutive prairie lupine. Lots of mosses and lichens are also growing in this photo. I took it down on the pumice plain, before we got to the crater. There are prairie lupines growing in the crater, but not Indian least not yet...

 I don't know what this flowering plant is, but it was growing near the crater. I learned something interesting about the cracked rocks I saw everywhere in the area. I thought they cracked because water got into cracks and froze in the winter, but the geologist explained that the cracks happened shortly after the eruption. The magmatic rocks were incredibly hot. As they cooled, the outside surfaces cooled at a faster rate than the rock's interior, and they cracked in the process.

 Grasses with seed heads growing near the crater.

A tiny Douglas fir growing near the crater.

The chorus frog was able to survive in this environment because there was a small glacial stream. The stream had some algae growing in it because of the minerals and heat from a nearby hot spring. The frog most likely eats algae and insects. The insects come because of the plants that are beginning to grow. I saw two spiders on the hike, one of them in the crater itself.

The post-1980 landscape north of Mount St. Helens has provided a unique laboratory for biologists to study primary succession. Which plants establish themselves first? What plants and animals begin to follow? What are the interactions between the various species?

We saw two herds of elk (no photos--sorry--they were too far in the distance for my little camera) down on the pumice plain. The biologist explained to us that most of the willows that are trying to grow in the area have broken tops because the elk rub their antlers against them to remove the velvet each year. At the same time, tiny little weevils have come into the area, and they attack the willows from the inside out. There is always a constant interplay between the flora and fauna in any region, but here, where the plants and animals have only gradually been reestablishing themselves, scientists have been able to observe their interactions in some unique ways.

In addition to food, the plants and animals need water. Of course there is lots of precipitation in the Northwest. In addition, two streams flow off the crater glacier.

So, the glacier. All morning long, this had been our goal. We would be eating lunch at the crater's snout. I had visions of sparkling ice with deep blue fissures. I think I must have been looking at ads for cruises to Alaska. This is what the Mount St. Helens crater glacier looks like:

 That dark gray flat thing in the distance? That's the glacier. It looks so...volcanic. Duh. It's covered with volcanic ash, grit, and rocks that come tumbling down from the crater walls.

 It's a very active glacier, growing (in length) more than 150 feet each year. (More this year, because we had so much snow.) This photo shows one of the streams coming off the glacier, and the active rock falls slithering down the face of the glacier.

It's hard to get a sense of scale. Everything is so big. The front of the glacier--the snout--is about 100 feet tall.
Face to face (snout to snout?) with the glacier. One of the things that fascinated me about being in the crater was how colorful the rocks were. Ok, they're still mostly shades of gray, but there are bright yellows, greens, and reds mixed in. The geologist explained that the closer a rock is to the effects of magmatism (near magma, heat, etc.) the more likely it is to be changed, and the crater rocks are newer, and showing the effects of their recent contact with magmatism. I confess...I hiked out with 3 or 4 small colorful rocks in my pocket. Please don't turn me in. I don't think the volcano will miss them...

I'd like to wrap up this post by explaining a little more about the structure of the Mount St. Helens crater. When most people envision a crater, they think of something like Crater Lake. Nice and round and symmetrical. But Mount St. Helens isn't like that. The south face of the mountain looks like that. That's the side that people are talking about when they talk about climbing to the summit of Mount St. Helens.

The north side of Mount St. Helens is another story. When it erupted in 1980, almost the entire north side blasted out laterally--to the side--heading north. If you're not familiar with that terrain, here are a couple of interesting videos to bring you up to speed.

This one is only 18 seconds long. It is composed from an amazing series of photos taken by amateur photographer Gary Rosenquist, who happened to be in the right place at the right time. Here is an explanation of his sequence of photos.

This one is 7 minutes long. If you can't spare the full 7 minutes of your life, then fast forward to about 4 minutes in. There's a really good animated diagram / explanation of the lateral blast.

Sunday morning at church, someone asked me if I had to know how to arrest my fall with an ice axe before I could go into the crater. I thought he was joking, until I realized he was thinking of a Crater Lake-ish crater. Hiking into the Mount St. Helens crater was a challenging uphill hike, but we weren't going over the lip of the volcano down into the crater below. We were hiking across the pumice plain and up the debris flow to the opening in the side of the mountain.

What was the coolest thing about being in the crater? Maybe it was just the realization that I was standing inside what had once been deep inside a mountain. As we were hiking up the debris field, in an area called the Goat Rocks fan, the geologist pointed out the moment when we "stepped inside the mountain," inside the imaginary line in the air that had once been the surface contour of Mount St. Helens.

No, I didn't get to see anyone up at the summit waving down at us. I had imagined that we would, because when Mark and I climbed to the (south side) summit a year ago, we had seen scientists about the size of ants way down below us in the crater. Due to the poor visibility, I doubt that anyone actually made it to the summit last Saturday, but if they did, they weren't seeing much of the crater.

I also didn't get to see the lava dome, which would have been a cool thing, but it's not accessible except by helicopter. It's back behind the glacier, which now walls off most of the crater. (It's the only glacier in North America that is growing, not shrinking.)

But I don't care. I was there, and I made it to the crater with a hard climb, in spite of the weather. I was inside the mountain, and I loved it.

Tomorrow: Stay tuned for the descent...and the mountain goat!


Dorothy said...

If you weren't already an English teacher...I'd think you might enjoy teaching SCIENCE. :) That would be cool to realize you were standing in a place that used to be the inside of a mountain.

Bridget said...

The part where you climbed the imaginary line to where the mountain used to be blew my mind! What an adventure.