Nevada
Next time you find yourself on a plane headed for Las Vegas, take a peek out the window just before landing, and you might catch sight of a premier geologic feature of the desert Southwest: Red Rock Canyon. Here, piles of ancient limestone and not-as-ancient brightly colored sandstone have conspired to create a mecca for rock climbers, adventurers, and anyone who needs a scenic break from the neon nightlife of The Strip.
Around 600 million years ago, what is now Las Vegas was underwater, at the bottom of an inland ocean basin. Over hundreds of millions of years, the calcium carbonate–rich remains of shelled creatures piled up on the seafloor, eventually leaving behind layers of sediments more than 9000 feet thick. With time, these layers compressed and lithified into limestone.
Fast forward to 180 million years ago, when the same ocean was a sea of sand. At that point, a vast desert of giant dunes covered the buried limestone layers. Some of these dunes were thicker than a half-mile and over eons, they compressed and lithified into sandstone. Between 70 and 40 million years ago, when an episode of mountain building called the Laramide orogeny was raising the Rocky Mountains to Himalayan heights, the extreme pressures generated by this large-scale deformation of crust gave rise to a number of thrust faults across the West.
Two of these faults, the Keystone Thrust Fault and the Wilson Cliffs Thrust Fault, run directly through Red Rock Canyon. Here, the thrust faults have displaced the older gray limestone, which now sits atop the younger red sandstone—an unusual exception to typical geology, in which older rocks sit beneath younger rocks.
Both limestone and sandstone are attractive to rock climbers, who come from around the globe to tackle the 2000-plus named climbing routes in Red Rock Canyon. The colorful, iron-rich sandstone is usually scaled using sport climbing techniques, in which climbers clip into bolts drilled into the rock. The limestone in the canyon is more often ascended using traditional rock climbing techniques, in which climbers must follow natural features in the rock, placing protective gear in cracks on their way up.
The canyon lies about fifteen miles west of Las Vegas’s McCarron International Airport. Look for the bright red and orange sandstone rocks that line the east side of the canyon. The gray limestone appears on the west side, with a scenic loop road in the middle.
