Specimen Ridge in Yellowstone National Park consists of many layers containing standing petrified trees. These trees were assumed to represent 27 successive forests which were each buried by volcanic eruptions, separated by long spans of time. If this is right, why do trees in different layers have the same ring structure? Where are the soil zones between forests? Why are the roots broken off? The 1980 Mt. St. Helens eruption answered our questions and altered our view of the formation of Specimen Ridge forever. It ripped up trees from a single forest and deposited them in mudflows and also in Spirit lake. There they became water-logged, sank to the bottom, and were buried upright in distinct layers as if they grew during different times.
By Dave Nutting
