Geography of Colorado
The Rocky Mountains within Colorado contain 54 peaks that are 14,000 feet (4270 m) or higher, known as fourteeners. The mountains are timbered with conifers and aspen to the tree line, at an elevation of about 12,000 feet (3,650 m) in southern Colorado to about 10,500 feet (3,200 m) in northern Colorado; above this only alpine vegetation grows. The Rockies are snow-covered only in the winter; most snow melts by mid-August with the exception of a few small glaciers. The Colorado Mineral Belt, stretching from the San Juan Mountains in the southwest to Boulder and Central City on the front range, contains most of the historic gold and silver mining districts of Colorado.
Denver Basin
The basin was most likely further deepened in Paleogene time, between 66 and 45 million years ago, during the Laramide orogeny that created the modern Colorado Rockies. In particular, the uplifting of the Rockies in the Front Range caused the crust near Denver to buckle downward on the eastern side, deepening the basin. The basin later became filled with sediment eroded from the Rockies. The Front Range peaks rise approximately 22,000 ft (6600 m) from the floor of the basin under Denver.