The Black Canyon of the Gunnison National Park is one of Colorado's most amazing geologic features. This is the deepest narrow canyon in North America (meaning that the canyon is deeper than it is wide - over 2,000 feet deep and as narrow as 40 feet at the bottom). The Gunnison River has been carving through the extremely hard 1.8 billion year old Precambrian gneiss and schist for 2-3 million years, resulting sheer walls that tower over 2,000 vertical feet above the river.