Geology of Canyonlands National Park, Utah: Sandstone, Salt and a Very Young Landscape

Part of the NPS Geodiversity Atlas, which describes each park's significant geologic features and processes, from the NPS Geologic Resources Inventory.

The park's Geologic Resources Inventory report. Image from the NPS's page.

The park

Canyonlands National Park protects 527 square miles (1,365 km²) around the confluence of the Green and Colorado Rivers in southeastern Utah. The rivers split it into three districts: the Needles east of the Colorado, the Maze to the west, and the Island in the Sky, a high mesa between them. Its treasures are a superbly exposed run of late Paleozoic and Mesozoic sedimentary rock and classic desert erosion landforms — canyons, arches, alcoves, mesas, buttes, spires, and the puzzling Upheaval Dome. It is far shallower than the Grand Canyon, but its canyon country rivals it.

The Green River Overlook. NPS photo.

The park lies in the heart of the Colorado Plateau — high, thick-crusted and little deformed — which covers about 130,000 square miles of Utah, Colorado, New Mexico and Arizona and holds 30 units of the National Park System. A dry climate and the cutting power of the two rivers have laid its rocks bare.

The rocks, oldest to youngest

The rocks were laid down between about 310 and 160 million years ago, in the sea and on land, while the Ancestral Rocky Mountains to the northeast wore away. Sandstone dominates, most of it wind-blown (eolian).

Salt that flows. Buried under the weight of later rock, the Paradox salt — up to about 6,000 ft (1,800 m) thick — creeps like putty, and being lighter than other rock it rises, doming the layers above. That made the salt anticlines along the Colorado and the Grabens of the Needles.

Uplift, then very fast erosion

These rocks formed near sea level but now stand up to 7,000 ft (2,100 m) high, and the youngest were once buried under another 4,000–6,000 ft (1,200–1,800 m) of rock since worn away. The rise came in stages:

• Laramide orogeny, 70–40 million years ago: the event that built the Rockies reached unusually far inland because a thick oceanic plateau on the Farallon plate made it slide under at a shallow angle. It raised broad folds such as the Monument uplift, which reaches into the park.
• 35–25 million years ago: hot mantle welled up above the sinking Farallon slab, and intrusions formed the La Sal, Abajo and Henry Mountains.
• The last 10 million years: further uplift from deep mantle processes, plus rebound as erosion unloaded the crust.

The canyons themselves are brand-new. Cutting began after the upper Colorado was linked to the Gulf of California, within the last 5 to 6 million years, and most of Canyonlands' erosion probably came in the last two to three million years, at rates of 1,300 ft (400 m) per million years or more — among the plateau's fastest. The river's downcutting drives erosion up its side canyons, and cliffs retreat by rockfall and sapping. Hard layers such as the White Rim and Kayenta cap mesas, buttes and spires, shielding the softer Moenkopi and Chinle beneath.

The Green River and the young landscape. NPS photo by Andrew Kuhn.

The Needles

Spires of Cedar Mesa Sandstone, cut where two sets of vertical fractures (joints) cross at nearly right angles and erosion widened them — best seen around Chesler Park. The Joint Trail threads joints 40–50 ft (12–15 m) deep. The Grabens look like straight-walled canyons but are not stream-cut: as Cataract Canyon deepened, salt flowed toward it, stretching the ground, and blocks dropped between parallel faults (more).

The Grabens from the air. NPS photo by Neal Herbert.

Island in the Sky

Nearly the whole rock sequence, from the river to the Navajo domes on top, in classic cliff-and-slope canyon country; a narrow Neck ties the "island" to the plateau. Grand View Point looks over the White Rim, a broad sandstone bench with a 99-mile (160-km) four-wheel-drive road. Upheaval Dome looks like a target from space: layers bowed into a dome around a crater-like basin. Whether rising salt or a meteorite impact made it is unresolved.

Grand View Point. NPS photo by Nicole Segnini.

Upheaval Dome. Photo: Doc Searls, Creative Commons Attribution 2.0.

The Maze

The most rugged and remote district, reached only by hard four-wheel-drive roads or on foot: a labyrinth of slickrock canyons in Cedar Mesa Sandstone. Spires of Organ Rock — the Land of Standing Rocks, the Chocolate Drops — rise below the Maze Overlook; the Doll House is jointed spires like Chesler Park's; Elaterite Basin is named for tar seeping from the White Rim. Separate Horseshoe Canyon protects important Barrier Canyon pictographs. Below the confluence, Cataract Canyon has some of the country's toughest whitewater.

The Land of Standing Rocks. NPS photo by Kait Thomas.

Fossils, alcoves, crusts and varnish

• Fossils: marine brachiopods, crinoids, bryozoans and corals in the older layers; petrified wood and vertebrates in the Chinle; dinosaur tracks in the Kayenta; Ice Age packrat middens in alcoves.
• Alcoves such as Cave Spring form where hard rock overhangs softer rock eroding at a spring or seep; people sheltered in them from ancient times to the cowboy era.
• Biological soil crust — cyanobacteria, mosses, lichens and more — is among the best developed in the world here. It feeds the soil nitrogen and holds it in place, but one footprint can destroy it for decades. Stay on trails, bare slickrock or dry washes.
• Springs and hanging gardens are rare, reliable water where porous sandstone meets a tighter layer.
• Arches include Mesa, Musselman, Druid and Wooden Shoe; dark desert varnish streaks the pale White Rim and Navajo sandstones.

The Cave Spring historic cowboy camp. NPS photo by Neal Herbert.

Soil crust damaged by footprints. NPS photo.

Paul Bunyan's Potty, a pothole arch in the Needles. NPS photo by Neal Herbert.

Hazards

• Rockfall, slope failure and flash floods.
• Earthquakes: a moderate hazard; the USGS gives a 2% chance in 50 years of shaking above 10–12% of gravity.
• Old mines: the area was the heart of the 1950s uranium boom; prospectors built roads such as the Shafer Trail and dug small mines, mostly in the Chinle, and oil and gas wells were drilled. The Park Service counts 74 abandoned mine features, including 24 sites, many needing cleanup — with radon, unstable workings and bad air. Stay out and stay alive.

Geologic map of the park, from the Geologic Resources Inventory. NPS.

The park's maps and reports are in the NPS DataStore, with a completed Soil Resources Inventory. More: Canyonlands geology.

Hikers above the canyons. Image from the NPS's page.

Sources

Based on "NPS Geodiversity Atlas—Canyonlands National Park, Utah," National Park Service; a work of the United States government in the public domain. The atlas's "Paul Bunyon's Potty" is corrected to Paul Bunyan's Potty. Its photographs and diagrams first published in Moab Happenings are not reproduced.