 Impressive landforms are visible in all parts of Wyoming. For example, just outside Green River Wyoming, this cliff is known as Castle Rock and the Palisades. It's pretty hard to visualize in the arid environment of today, but sediments in these cliffs of sandstone and claystone were deposited in a huge lake that covered much of southwest Wyoming 55 to 50 million years ago. At that time, most of the mountains in Wyoming had been uplifted and were starting to erode. In this corner of the state, sediments and minerals washing down from the new mountains were impounded in a warm shallow lake that teamed with tropical plants, millions of fish, crocodiles, and other critters. Over time, the water in this ancient lake evaporated, as a result the world's largest known deposit of Trona mineral accumulated in this region. Trona is used in many products including glass, soap, paper, and baking soda, and about 90% of our nation's supply of Trona comes from this old lake bed. Thousands of people are employed in Trona mining, and it is a very important export for our state and the nation. Whether you find these landforms magnificent or unattractive, they are a very important part of Wyoming's geologic and economic story. I'm Tom Hill from the University of Wyoming Cooperative Extension Service exploring the nature of Wyoming.