Dakota Hogback

The Dakota Hogback is a long hogback ridge at the eastern fringe of the Rocky Mountains that extends north-south from southern Wyoming through Colorado and into northern New Mexico in the United States. The ridge is prominently visible as the first line of foothills along the edge of the Great Plains. It is generally faulted along its western side, and varies in height, with gaps in numerous locations where rivers exit the mountains. The ridge takes its name from the Dakota Formation, a formation with resistant sandstone beds that cap the ridge. The hogback was formed during the Laramide orogeny, approximately 50 million years (50 my) ago, when the modern Rockies were created. The general uplift to the west created long faulting in the North American Plate, resulting in the creation of the hogback.^[1]

While the hogback was created during the Laramide Orogeny, the geologic strata comprising the hogback are much older. For example, fossilized data such as

Before the mountains, the region was a shallow sea. As sediments fell to the bottom of the water, they were compressed into soft sedimentary rock. Thus, oyster and clam shells, sand, and mud built slowly into layers of sandstone, shale, limestone, and "mudstone."^[3] As the Rocky Mountains rose over the last 67 million years, up to nearly 30,000 feet above sea level, the soft sedimentary rocks were quickly weathered and washed away from the high mountains. But on the edge of the foothills, where the layers were scraped and pushed only slightly upward, the western edge of their remnant still stands at about a 45-degree angle - the Dakota Ridge.^[3] The top layer is a hard sandstone, the Dakota Sandstone, from which the ridge gets its name. It protects the softer shales and limestones beneath it from weathering and erosion.^[3]

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