In the northwest corner of Colorado, the west-flowing Yampa River meets the south-flowing Green River, which runs into Utah. Stretches of both river canyons upstream and downstream from the junction make up Dinosaur National Monument. The monument takes its name, of course, from the abundant fossils found in exposed valleys and low ridges of the Morrison Formation, a series of rock layers that were formed late in the Jurassic Period, roughly 145 million years ago.
Published Oct 1, 2007
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