Colorado National Monument (Part 2)

The rock layer visible near the top right is the Entrada Formation. This smooth salmon-colored sandstone formed from sand dunes blown from the shores of an inland sea in central Utah 165 million years ago during the Middle Jurassic. It is split into the Slick Rock Member and the thinner, lighter-colored Board Beds Member that overlies it. The Entrada Formation can be seen next to and above Rim Rock Drive and is the same layer responsible for most of the arches at Arches National Park. Above the Entrada Formation is the Wanakah Formation, a thin layer of crumbly, brick red rock (mudstone, sandstone, and green shale) deposited as a shallow lake repeatedly expanded and dried up 160 million years ago during the Middle Jurassic. It can be seen by the road at Artists Point.

Over the Entrada Formation and Wanakah Formation lies the Morrison Formation. It is composed of multicolored sedimentary rocks formed from lake, stream, and floodplain deposits 150 million years ago during the Late Jurassic. The bottom Tidwell Member (sandstone and green mudstone with thin limestone lenses) formed as an ancient delta built out into a shallow lake. The middle Salt Wash Member (sandstone with some red to green mudstone) was deposited by the stream channels that eventually extended across the area. The top Brushy Basin Member (red, green, purple, and gray mudstone and bentonites with some sandstone lenses) includes stream and floodplain deposits along with layers of volcanic ash from ancient volcanoes to the west. The Morrison Formation can be seen in upper elevations along Rim Rock Drive and on Black Ridge Trail. It is well known for abundant dinosaur fossils found at locations such as Dinosaur National Monument.

The last rock layer found within Colorado National Monument is the Burro Canyon Formation. This is rough greenish rock (sandstone, conglomerate, and green shale) formed from stream and floodplain deposits 140 million years ago during the Early Cretaceous. It can only be seen from Black Ridge Trail. 

The canyon walls sink to depths of 500 feet in some places.

The Coke Ovens are a set of rounded pillars named for their resemblance to nineteenth century beehive ovens used to convert bituminous coal into coke, which was then used for smelting iron. These monoliths lost their Kayenta Formation caprock, which exposed the softer Wingate Sandstone to erosion and produced their rounded shapes.

The first road into Colorado National Monument was completed under Superintendent John Otto in 1921. Serpents Trail was called the world’s “crookedest road” for the 54 switchbacks over its two and a half miles. Although the road increased accessibility to the monument, it only brought visitors into the east side. After Rim Rock Drive was completed, Serpents Trail was closed to motorized vehicles and became a hiking trail.

In 1925, John Otto introduced bison into the monument after acquiring two cows and a bull. The bison herd grew to as many as 45 animals but generally maintained around 20-25 animals. In 1983, concerns over conservation of vegetation led to the bison being moved to Badlands National Park. 

Flash flooding and water seepage eroded the Chinle Formation at the base of the cliff while repeated freezing and thawing of water expanded a crack in the rock until a large slab separated from the cliff. Over the course of centuries, Fallen Rock slowly slid more than 100 feet down to the debris slope below. It likely came to rest at its current position thousands of years ago.

National Park Service Engineer Thomas W. Secrest determined the route of Rim Rock Drive in 1931. Most of the road was built by laborers from the Works Progress Administration, Public Works Administration, and Civilian Conservation Corps. In 1933, nine workers were killed when overhanging rock at Half-Tunnel collapsed. Two men were also killed in other separate accidents. Work on the road was suspended between 1942-1948 due to World War II, but it was finally completed in 1950. In 1994, it was designated a historic district on the National Register of Historic Places.

In the 1980s, Colorado National Monument gained attention for its inclusion as a stage of the annual Coors International Bicycle Classic. The section of the race through the monument became known as “The Tour of the Moon."

Red Canyon is a broad U-shaped canyon that has a smaller V-cut at the end to give it the appearance of a “canyon within a canyon.” The dip into the valley caused water to flow faster at the far end and wear away the notch. Since it has reached the harder Precambrian rock layer, the V-cut will grow longer and wider rather than deeper.

Since 1907, there have been several attempts to have Colorado National Monument redesignated as a national park, with the most recent being in 2014.