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Mount Crested Butte owes its existence to a massive volcanic episode that roiled Colorado 30 million years ago. —Photo by Terri Cook

Colorado by Nature: Why You Can Ski Crested Butte

Without massive volcanic activity and the help of several glaciers, Crested Butte’s famously steep terrain would not exist.

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Of all Colorado’s ski resorts, Crested Butte is best known for its extreme terrain. In addition to Rambo, whose 55-degree pitch comprises North America’s steepest in-bounds ski run, the mountain’s upper face, plus the adjacent Teocalli and Third bowls, are filled with notoriously steep double-black diamonds with memorable names like Banana, Staircase, and Sock-It-To-Me Ridge.

Yet not one of these insanely steep runs—nor the resort’s extensive intermediate and beginner terrain—would exist if it weren’t for a fortunate series of geologic events that began about 30 million years ago. At that time, an enormous episode of volcanism, whose volume was at least 200,000 times larger than the 1980 eruption of Mt. St. Helens, was roiling a region stretching from Colorado to central Nevada. Although some of this volcanic material punched all the way through the crust to erupt at the Earth’s surface, much of the molten magma didn’t quite make it that far.

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In the Crested Butte region, which was blanketed by a thick stack of sedimentary layers, this magma came close to the surface in several spots. Perhaps half a mile below the surface, however, it began to spread out horizontally, forcing its way between some of the sediment layers and causing the overlying rocks to dome up into huge, mushroom-shaped blisters. Over hundreds of thousands of years, this magma slowly cooled into large pods of light-colored granite.

During the intervening millions of years, Mother Nature slowly stripped away the domed-up layers, gradually exposing the much harder granites. In the Elk Mountains, where Crested Butte is located, many of the volcanic rocks were also removed, leaving behind only the bowels of these ancient volcanoes. In addition to Mt. Crested Butte, the other jagged peaks surrounding the resort, including Mt. Axtell and Whetstone, Snodgrass, and Gothic mountains, are all remnants of this same volcanic episode.

The finishing touches to Mt. Crested Butte’s terrain occurred just 20,000 years ago, when large glaciers flowed down the East and Slate river valleys, completely surrounding what is now the resort. Thanks to the granite’s hardness, even the largest glacier only struck the mountain a glancing blow, carving a cliff so sheer on the southwest side that, even at Crested Butte, it is too steep to ski. Luckily, small glaciers also formed at several spots on the mountain’s highest north-facing slopes, carving out the acclaimed bowls that both die-hards (and more sane skiers like myself) so enjoy.

(Read more about the geological history of Colorado’s beautiful spaces)

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