Colorado
The Front Range, the eastern boundary of the Colorado Rockies, rises abruptly out of the eastern plains.
Long before its legalization of marijuana, Colorado was the highest state in the lower forty-eight, boasting fifty-eight peaks exceeding 14,000 feet. The peaks, many of which hold snow year-round, are unmistakable from above, stretching across the state in a band that arcs from the Front Range north and west of Denver to the San Juan Mountains in the southwest part of the state.
The Colorado Rockies, the southern section of the U.S. Rockies, were uplifted between 70 and 40 million years ago, during a prolonged episode of mountain building (the Laramide orogeny), which raised the Rockies to heights over 20,000 feet. The driving forces of the uplift remain somewhat mysterious, however. Geologists know that 1000 miles to the west, at least one oceanic plate—the Farallon Plate—and possibly another, were being forced under the North American Plate during this time period. Subduction zones often form mountain ranges 200 to 400 miles inland, but the Rockies are twice as far away. So how could such a distant tectonic event create such huge mountains?
The answer may lie partly in an ancient mountain range known as the Ancestral Rocky Mountains, which existed around 300 million years ago, when amphibians ruled widespread swamps and dinosaurs had not yet evolved. During this time, what is now Colorado was home to two mountainous regions called Frontrangia and Uncompahgria, which were located where the Front Range and San Juan Mountains are today. Perhaps the hard roots of these mountains played some role in uplifting the region to Himalayan heights during the Laramide orogeny.
This satellite image of the Front Range of the Colorado Rockies was taken in high summer, when the peaks are almost devoid of snow.
The Colorado Rockies today have been eroded down approximately 6000 feet from their maximum heights, exposing a mishmash of Precambrian metamorphic rock, fossil-rich rocks from the Permian Period, and conglomerates and sedimentary rock from the Mesozoic Era. Nearly sixty peaks still top 14,000 feet, however, and this variety of rock types gives many of Colorado’s fourteeners unique profiles. The Maroon Bells, near Aspen, are composed of reddish, rotten, unstable mudstone that makes them some of the most difficult and treacherous fourteeners to climb. At the other end of the spectrum is Mount Elbert (the highest fourteener at 14,439), near Leadville, made up of very hard quartzite that lays the groundwork for an easy stroll to the summit.
Colorado has more fourteeners than any other state, followed by Alaska with twenty-nine, California with twelve, and Washington with two. None of the other states that host the U.S. Rockies—New Mexico, Wyoming, Montana, or Idaho—has any peaks reaching 14,000 feet.
The state of Colorado is home to fifty-eight peaks higher than 14,000 feet (fourteeners), grouped into seven mountain ranges.
Hard quartzite juts out of the ground near the summit of Mount Elbert, the highest of the Colorado fourteeners.
You will fly over the Colorado Rockies en route to Denver, specifically, but also on many U.S. cross-continental trips.
