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Under construction Tower Falls to Dunraven Pass Mt. Washburn and its pyroclastic flows Paul explaining how the andesitic lava from Mt. Washburn flowed into this area. As andesite, it weathers and becomes rich soils supporting grasses (which displace trees), white bark pine, and other vegetation which also attracts megafauna such as grizzly bears and elk. This area is often populated with grizzlies as opposed to other side of Mt Washburn which is inside the Yellowstone Caldera (we are outside of it here) and which is composed of rhyolite lava which makes a less nutrient rich soil. The predominant plant life on rhyolite is the lodgepole pine which provides much less nutrients to large mammals. The apparently never ending forest of lodgepole pines has been termed as forests of pinus monotonous.
Here you can see the relationship of Mt. Washburn to the pyroclastic flows by the road. As we traverse past Mt. Washburn on the right in this picture, we will cross Dunraven Pass which is adjacent to the Yellowstone Caldera. Pyroclastic flows as shown in these pictures can move up to and above 100 miles per hour. While no one was around (we think) to see these particular flows, it is likely that they had a lot of energy as noted by the large "grain" sizes of the elements in the flows (the material appears quite "chunky" - I hate to use technical terms but sometimes that is the best way).
Before we leave, we see a native grizzlie (with cowboy hat!) along side a whitebark pine (5 needles in a bundle for those wanting to identify the tree). In the fall, the grizzlies will sniff out caches of the nuts (cones) that squirrels would have hidden away. Apparently that is considered to be a calorie rich treat for the bears preparing to hibernate.
Here we are at Dunraven Pass. Paul is invoking the volcano gods to once again unleash the forces of darkness and give us a new eruption event for the class. Fortunately for us, the Lord of the Rings incantations do not work this day. They will appear to have taken effect in Norris Basin when we visit there tomorrow.
Here is the view from Dunraven Pass on the side looking into the caldera (a largely eastward view).
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