More than 250 million years ago, in the Triassic period, what is now western Utah was a broad coastal flat of the supercontinent Pangaea. The Moenkopi Formation, as it is known, saw five million years’ worth of sedimentary layers—gypsum, siltstone, mudstone—dumped onto the flats by oceans and rivers.

　　Nearly 200 million years later, the gradual seismic uplift of the Colorado Plateau produced a rugged topography, sculpted over time by wind and water into a craggy collection of buttes, canyons, and mesas. Today that ancient sedimentation, hoisted upward and exposed to air, is visible in the form of striking multi-hued bands.

　　One of those uplift features, known as Gooseberry Mesa, just south of Virgin, Utah, is a huge flat-topped butte with a towering 5,200 feet of elevation, prized by mountain bikers for its lunar-like slickrock surface. Trailing away from Gooseberry like an alligator tail is a long, thin, jagged ridge that has lost its protective caprock surface. In the slow march of geologic time, it is crumbling away.

　　For the past two years, this ridge has been home to Red Bull Rampage, the world’s most famous—some might say infamous—freeride mountain-bike event, which each year generates a torrent of jaw-dropping footage, streamed live to hundreds of thousands of viewers, along with hand-wringing social media posts from fans and pundits wondering if this is the year it all went just a bit too far.

　　Like its counterpart in snowboarding, freeriding began as a maverick pursuit, with early-nineties mountain bikers attempting to ride the seemingly unrideable. “We sent it as raw as we could,” says Brett Tippie, a former pro who helped pioneer the sport in Kamloops, British Columbia. “We might kick a few stones out of the way, but it was basically raw mountain.” The first Rampage, in 2001, had the same DIY spirit, but over time the lines have become more engineered, the runs more flowy and trick filled, the jumps bigger and the stakes higher. To date, no one has died at Rampage, but serious injuries are not uncommon—in 2015, a crash left the rider Paul Basagoitia paralyzed.

　　The goal of Rampage is to descend from a wooden platform just below Gooseberry Mesa to the finish corral, more than 600 feet below, in less than three minutes. Riders get two chances. Along the way, navigating that ancient sedimentary geology, they perform any number of tricks, from Supermans to suicide no-handers, no-foots to nac-nacs, tailwhips to front flips. Each ride is scored on the difficulty of the line, control and fluidity, air and amplitude, and style.

　　(Rampage, much to the ire of the freeride community, has always been an all-male affair. This year, Red Bull halted its fledgling women’s event, called Formation. The company says it’s “postponed” and is working on an eventual return.)