Today we visited Stratigraphy Viewpoint. The view was fantastic! We had seen Mt. St. Helens from a distance, but never this close. Our job was to document the different layers of sediment and pumice. The layers were exposed when Mt. St. Helens had a volcanic eruption. The heat of the eruption caused Shoestring Glacier to melt creating a massive amount of water, which collected with pumice, sediment, and other rocks. The end result was a lahar which altered the land and built the layers that we saw today. Each group was given a specific area to document and the teams had to work together to draw, describe, measure, identify rocks, describe the matrix, and give reasoning and their interpretation. Since each section is unique, we all had different data to present to our group. For example, our group observed layers caused by an air fall tephra (mainly rocks with some sediment) and a pyroclastic flow (mainly sediment). Our first layer was about three feet and ten inches, and caused by an air fall tephra. There were many different colors of tiny pumice in this layer alone. From the bottom going up, we had brown, dark orange, light orange, and tan, resulting in a multi-color layer. Other groups, however, had the aforementioned layer later on, as their first layer was created by a lahar. This layer had big jagged rocks and a uniformed tan color. The most interesting layer was caused by a pyroclastic flow. It was sediment that looked like it had brushstrokes carved into it. It was a light gray that crumbled easily. By the end of the data collection, we not only learned about different layers of sediment and pumice, but we were able to see how the stories hidden in the rocks can reveal the history of the mountain.

Your GeoGirls,

The Power Parrots

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