Extinction and Dinosaur National Monument
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Dinosaur National Monument lies in western Colorado and eastern Utah. The key rocks were deposited in swamps and along rivers during the Jurassic in the middle of the Mesozoic, and are called the Morrison Formation. Before the modern Rockies were raised, sluggish streams flowed across the basins of this region, with numerous low, wet floodplains. Dinosaurs flourished. After some died, their bodies were washed up on sandbars, where their bones were buried before scavengers and gnawers could consume the bones. Over time, minerals carried in groundwater reacted chemically with the bones, depositing silica in them. (For a little more on petrification, see the Module 11 Enrichment—no magic is involved, and replacement by stone is a normal process that really is expected to occur in some places!)
After the bone was turned to stone at what would become Dinosaur National Monument, the rocks of the region were raised and tilted during the mountain-building that formed the Rockies. Streams, including the Green River, cut through the rocks. The Canyon of Lodore on the Green is a favorite destination for serious white-water rafting. The first scientist in the region was John Wesley Powell, who went on to run the Grand Canyon. In 1909, workers from the Carnegie Museum of Pittsburgh found Dinosaur Ledge, a sandbar-turned-to-stone on which many dinosaur bones had been deposited and fossilized. Today, some of those petrified bones are on display in the Carnegie Museum and in other great museums, but many of the bones have been left on the ledge to be viewed in the park (see the picture above).