This canyon was formed by flowing water, not by glaciation. Its shape reflects different rocks responding to erosion in different ways: while the Colorado River eroded the Mancos Shale in the valley relatively quickly, tributary streams in the canyons cut through harder rock more slowly. As a result, the difference in elevation between the Grand Valley and the Monument's canyons increased, creating hanging canyons such as this one. After the canyon's stream cut through the softer sedimentary layers of the Kayenta, Wingate, and Chinle Formations, it reached the hard basement rock of the canyon floor, where downward erosion nearly stopped but horizontal erosion continued. At the far end of the canyon, where the valley floor dips downward and the stream flows faster, a prominent notch was eventually carved, and today rockfall from adjacent cliffs and sand and gravel from upstream cover much of the valley floor.