For our last day on the river, we climbed into Kelly’s boat. We had already ridden with her through Warm Springs rapids, but we wanted to ride with Emmett for a final geology “lesson” and he had not been in her raft yet. What a lesson we got! As we moved through each rock formation, Emmett would describe the terrain millions of years ago that had created the geologic conditions that, in turn, had created the rock types and layers.
Early on we came to the mouth of Whirlpool Canyon, which is marked by the Island Park fault. Here sharply folded Round Valley limestone and Morgan formations (of Mesozoic Pennsylvanian times) dive into the river and are replaced by younger (Jurassic and Triassic eras of the Cenozoic age) Glen Canyon sandstone.
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