Utah
Few established trails lead to the interior of the swell and the confusing landscape is best left to expert navigators.
Utah has its fair share of national parks, but one of the most spectacular landscapes in the state isn’t a national park or even a national monument. The San Rafael Swell, located about sixty miles due west of Moab, is an uplifted dome of sandstone, shale, and limestone, seventy miles long and forty miles wide. You can spot the dome from the air—its white, jagged teeth jut out of the desert just south of Interstate 70—in country so intimidating, there’s never been a need for federal protection from development.
An uplifted dome of many layers of sandstone underlies the San Rafael Swell, which has been deeply dissected by slot canyons carved by flash floods.
In geologic terms, the San Rafael Swell is an anticline: an upwarped fold in the crust that looks like a dome when viewed in cross section. The rocks of the swell formed around 160 million years ago, after the region’s inland sea had evaporated. Between 70 and 40 million years ago, when the Rocky Mountains were rising to the east, the San Rafael Swell was uplifted by the same forces working deep in the planet’s mantle. As the top and sides of the dome split and fractured, rainwater found its way into the cracks, eroding them deeper and forming a convoluted network of slot canyons that drain the swell, some only a few feet wide but hundreds of feet deep.
The eastern side of the swell, the San Rafael Reef, is the most dramatically angled and fractured part of the dome. Made up of steeply tilted layers of erosion-resistant white Navajo Sandstone and red Wingate Sandstone, these hard rocks have formed into upright fins, sheer cliffs, and deep canyons.
A few of the reef’s slot canyons are passable on foot, but others require technical rappelling gear to navigate their twisting corridors. The best beginner slots are Ding, Dang, Little Wild Horse, and Bell Canyons, with Music and Eardley Canyons requiring ropes, harnesses, rappelling racks, and route-finding experience. The danger of flash floods in these canyons is high, with no chance of escape from rising waters. Slots can flood even when blue skies are directly overhead. Fast-moving thunderstorms hit miles away, sending water rushing downhill, funneling into the slots.
Ding Canyon is one of the few slot canyons in the San Rafael Swell that doesn’t require technical climbing. It links to Dang Canyon for a five-mile loop.
Rippled sandstone forms when water creates ripples in mud (suggesting the area was once an inland sea), and the mud hardens into stone.
The eastern side of the San Rafael Swell, made up of erosion-resistant white Navajo Sandstone and red Wingate Sandstone, is nicknamed the San Rafael Reef for its jagged appearance.
The rest of the San Rafael Swell can also be explored on foot, and by navigating the maze of tilted layers with all-terrain vehicles on a few roads and trails, including Behind the Reef Road. Parts of the swell have appeared in movies as stand-ins for Mars and other exotic worlds. The Mars Society, dedicated to the exploration and human settlement of the Red Planet, has a Mars Desert Research Station in the San Rafael Swell, where they run survival simulations and conduct research projects.
You might fly over the San Rafael Swell en route to Salt Lake City or Moab, Utah.
