Today, we hiked to the Pumice Plain. We saw outcrops, elk paths, and even a *really* close-up view of Mt. St. Helens. We stopped when we reached an ideal spot to conduct an experiment on the layers of a pyroclastic flow. To find out when the different layers were produced all five of us carved five rocks out of the one of the different layers of the outcrop. Then, all of the teams broke open their rocks with hammers to see the color inside. After that, we sorted the rocks by interior color. Based on the in the color of the rock, we were able to deduce when the layers were created. The bottom layer was created by the May 18th, 1980 eruption. Since this explosion was very large, actually blowing apart around 1/3 of the entire mountain, we could tell this layer was from that eruption because it had so many different kinds of rock from all over the mountain. Both the middle and top layer were created by the later, smaller explosions. These explosions were primarily from the lava dome in the crater, so the layers they created were mostly the type of rock formed when the lava of the dome cooled. This rock was called dacite.

Breaking rocks open with a rock hammer
Breaking rocks open with a rock hammer

After that, we hiked back to our cars, then stopped to use the restroom and climb the 444 steps to the Windy Ridge Viewpoint. Fortunately, the view was worth it. We could actually see four mountains: Mt. Adams, Mt. Hood, and of course, Mt. St. Helens. We were pretty tired after all that hiking (our total mileage came up to around nine miles!), but we were exhilarated after seeing such great views . . . and getting back to camp for a much-anticipated dinner.

Your GeoGirls

The Power Parrots