Black Canyon of the Gunnison National Park, in the western part of Colorado, is a United States National Park and is managed by the National Park Service. The park has two entrances; the south rim entrance, 15 miles east of Montrose, and the North rim entrance, 11 miles south of Crawford. The south rim entrance is the more developed of the two, the north rim is closed during the winter. The park has within its borders 12 miles of the 48 mile canyon that spans the Gunnison river. The deepest and more dramatic sections of the canyon lay within the Black Canyon Park, though the canyon does stretch downstream into the Gunnison Gorge National Conservation Area, as well as upstream into the Curecanti National Recreation Area.
The average drop of the Gunnison River through the canyon is 43 feet per mile, marking it as one of the steepest mountain descents in N. America. By contrast, The average rate of drop for the Colorado River through the Grand Canyon is only 7 1/2 feet per mile. The steepest part of the river is at Chasm View, dropping an impressive 240 feet per mile. The Black Canyon gets its name from the lack of sunlight in the canyon's lower reaches due to its steepness. The walls are often draped in shadow, causing them to appear black. The canyon is a mere 40 feet across at its narrowest point.
The force of the Gunnison River is primarily responsible for carving the canyon, though several other geologic processes contributed to how the canyon appears today.
The Precambrian gneiss and schist, the primary substances in the makeup of the canyon's walls, formed 1.7 billion years ago during a metamorphic period created by a collision of ancient island volcanic island arcs with the southern end of modern Wyoming. The pegmatite dikes, lighter sections intersecting the base rocks, also formed during this area.
The entire area encompassing the canyon experienced an uplift during the Laramide progeny from 70 to 40 million years ago. This event lifted the Precambrian gneisses and schists that make up the canyon walls. The Tertiary period, from 35 to 26 million years ago, brought major volcanic activity to the region around the Black Canyon. The West Elk Mountains, La Sal Mountains, Henry Mountains, and Abajo Mountains all experienced volcanic activity which buries the area in ash and debris.
The course of the modern Gunnison River began 15 million years ago as run-off water from the La Sal and West Elk Mountains, as well as the Sawatch Range, carved its way through the soft volcanic rock.
With the river's course set, an uplift in the area 2 to 3 million years ago caused the river to cut through the soft volcanic material. The river eventually cut through the volcanic deposits and reached the Precambrian rocks of the Gunnison Uplift. As the river could not change its course, it started to cut through the harder rocks of the Gunnison Uplift. The river's flow was much stronger then, and the water contained more particles. Consequently, the river cut through the Precambrian rock at a rate of 1 inch per 100 years. The hardness of the rock combined with the speed at which the river carved its way through formed the steep walls seen today in the Black Canyon.
The Ute Indians had been aware of the canyon for many years before Europeans saw it. By 1776, when the United States gained its independence, two expeditions from Spain had found the canyons. In the 1800s, many fur trappers assuredly knew of the canyon, though there was no written record. The canyon had thoroughly explored by the late 1800s, early 1900s. The area was classified as a U.S. National Monument on March 2, 1933 and established as a National Park on Oct. 21, 1999.