Colorado Piedmont

The Colorado Piedmont is an area along the base of the foothills of the Front Range in north central Colorado in the United States. The region consists of a broad hilly valley, just under 5000 ft (1500 m) in elevation, stretching north and northeast from Denver in the valley of the South Platte River, as well as along the Arkansas River valley southward from Colorado Springs. The region includes much of the populated and cultivated area of Colorado. The name Colorado Piedmont also refers to the physiographic section of the Great Plains province.

The Colorado Piedmont elevation is lower than the foothills, but is also slightly lower elevation than the High Plains to the east. According to current geologic theory, the Piedmont was formed approximately 28 million years ago, during the broad bowing of the North American Plate that lifted the continent between present-day Kansas and Utah to its present elevation of approximately 5000 ft (1500 m). This uplift resulted in increased streamflow and rapid erosion on the eastern side of the Rocky Mountains. The erosion scraped away the top layer of Upper Cretaceous sandstone (which still exists as the top layer on the High Plains), exposing the underlying layer of Pierre Shale, which had been formed during the Cretaceous, when a shallow sea covered present-day Colorado. It was during this time that the South Platte River, which had previously flowed eastward across the Plains, rerouted northward along the mountains to join the Cache la Poudre River. In some areas of the Piedmont, a loose veneer of gravel overlays older shale and which accumulated during glaciation in the mountains, when streams descending onto the Piedmont became overburdened with sediment.

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