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Over 50 million years ago, during the Eocene Epoch, volcanoes in what would one day be the western United States were erupting and depositing ash in western Wyoming. At this same time, the Rocky Mountains began to form as the earth buckled and uplifted. Heavy rains which drained off of this new mountain range created Lake Gosiute, which covered an area of about 15,000 square miles, and drained an area of approximately 48,500 square miles. Over millions of years, Lake Gosiute expanded and contracted in response to changes in the region’s climate.
The volcanic ash which was deposited was high in sodium, and the decaying plant material in Lake Gosiute produced an excessive amount of carbon dioxide. The increased temperature under the surface and the mixture of sodium, carbon dioxide, and other minerals caused the precipitation of trona and oil shale. This process took several million years to complete.
Today, the results of this time can be seen in the trona mines to the west of this location, and the Green River Formation, which contains many fossil fish and other fossil species from Lake Gosiute.
To log this cache:
1) Using information given at this site, email me the answer as to how many millions of years the volcanoes deposited ash in this area.
Please consider posting photos of yourself, or the local geology, when you log this EarthCache. Photos can be an additional rewarding part of your journey, but posting them is not a requirement for logging this EarthCache, and is strictly optional.
BLM Informational Sign at Site
Black Hills Institute of Geological Research web site on the Green River Formation: (visit link)
OCI Chemical corporation, The OCI Story: (visit link)
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Coordinates are in the WGS84 datum