Each year since 1922, a group of roughly 30 hardy mountaineers known as the AdAmAn Club has scaled Pikes Peak’s steep, icy slopes on the last two days of December. From the summit, at the stroke of midnight on New Year’s Eve, the group sets off a stunning fireworks display to usher in the New Year. In good weather, the pyrotechnics can be seen from hundreds of miles away.

Now in its 93rd year, this celebration—from a human perspective—is a long-standing tradition. But 93 years is just the blink of an eye when compared to the history of the rocks the club has to climb to get to the top. The lofty mountain is composed entirely of granite, a light-colored rock whose coarse crystals cooled very, very slowly—over at least hundreds of thousands of years—from a blob of molten magma located several miles beneath the Earth’s surface, where it was insulated by the surrounding rock.

Pikes Peak is by far Colorado’s largest single body of granite, a unit so large that it’s exposed over 1,200 square miles and, based on magnetic evidence, extends even farther underground. And although granite is a pretty common rock in the Earth’s crust, the Pikes Peak granite is rather unusual. It is the only rock in Colorado—and one of only a few in the entire American West—that’s 1.08 billion years old.

Colorado has many other examples of granite, but most formed much earlier, between about 1.4 and 1.7 billion years ago, when the forces of plate tectonics were roiling the region. How exactly such a large, uniform mass of granite came to form hundreds of millions of years later, during a period of time when the area was tectonically quiet, is a geological mystery and an area of active research for many scientists in the state.

There are a few tantalizing clues that suggest the Pikes Peak granite may have formed at a hot spot, like modern-day Yellowstone, or that it may have been generated in an area where the Earth’s crust was slowly being pulled apart, like today’s East African Rift—or, perhaps, both.

One thing, however, is certain. The beauty and uniqueness of the New Year’s Eve fireworks display is a fitting tribute to the grandeur and history of the rocks from which they’re launched.

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

Terri Cook
Terri Cook
Terri Cook is an award-winning freelance writer based in Boulder. More of her work can be found at down2earthscience.com.