Elk Mountains and West Elk Mountains
The Elk Mountains and West Elk Mountains appear to be westward continuations of the Sawatch Range. Structurally, however, they are not faulted [anticlines] like most of the other ranges in Colorado, but are composed of a series of layers of Paleozoic sediments thrust westward over one another. These rocks, often crumpled and highly metamorphosed, are cut by numerous sills, [dikes], and other intrusions, many of which have caused mineral enrichment locally.
At Maroon Bells, in the canyon of Maroon Creek, and at Redstone on the Crystal River, these metamorphosed sediments are well exposed. Here, red sandstones and shales have been altered to quartzites and slate. At Marble, metamorphism of a thick limestone bed has produced white marble of great beauty, known as Yule Marble. This decorative stone was quarried extensively until about 1940. It was used in the Lincoln Memorial and several other monumental structures; in the town of Marble it has been used for the doorsteps of log cabins! The largest block quarried, for the Tomb of the Unknown Soldier in Arlington National Cemetery, measured 14 by 7.4 by 6 feet in the rough, and weighed 56 tons.
Mt. Sopris, south of Glenwood Springs, is an igneous intrusion. (Jack Rathbone photo)
Crested Butte, at the south end of the Elk Mountains, is a small intrusive igneous mass called a [laccolith]. Hard and resistant to erosion, it stands over 2,000 feet above the adjacent valley floor.