Arches, Canyonlands, Capitol Reef National Park, Utah

Arches, Canyonlands, Capitol Reef, Utah

This information and these images are taken from "Scenic Wonders of America," a Reader's Digest book published in 1973.

The region of the Colorado Plateau is vast with sculptured red rocks and varied landscapes. The red rock is primarily sandstone, uniform grains of 99% pure quartz, cemented by infiltrated iron oxide. The red color is in the cement alone, not in the clear grains. The Colorado River and the wind is primarily responsible for the landscape of these areas full of mesas, buttes, spires, pinnacles, domes, fins, knobs, towers and canyons. Stripped of topsoil and vegetation, the stones are the bare, chiseled bones of the earth. The canyonlands are semidesert: summer days are hot and the sun glares relentlessly. The colors are hot too: reds, brown and buff, mostly untempered by green.

Arches National Park is located in Moab, UT. This park has the greatest concentration of natural arches in the world (88) including a large assortment of other sandstone formations. Delicate Arch shown in the figure is found in Arches National Park. It is perhaps the most famous feature in the park perching on the rim of a giant sandstone bowl framing the distant La Sal Mountains. Delicate Arch is not the largest arch, but with its spraddle-legged stance on the rim of a smooth and spotless natural amphitheater it is an extraordinary sight. The most remarkable single formation is called Landscape Arch. It spans 291 feet, which makes it the largest arch in the world. It is unusually flat and bulkiest at the middle.

Water in the Desert Is the Principal Arch Builder

Natural bridges and arches are among the most eye-catching of erosional forms, but they are created in quite different ways. A bridge results from the cutting power of a deeply entrenched and meandering stream. Occasionally the stream will break through the divide between two wide loops to form a hole, which is then enlarged by weathering into a bridge. Arches, however, are formed by the erosion of a narrow "fin," or sandstone wall, as shown here. In the first phase the earth upwarps, cracking (or jointing) the sandstone.

In phase 2 the cracks are widened by rain and other weathering agents, while at lower levels alternate frost and thaw flake away the damp surfaces.

In phase 3 these processes cut through a fin to form a hole, which is enlarged by rockfalls until an arch is formed. Surface weathering rounds the shapes. (Contrary to popular belief, the effects of sandblastin have little to do with arches.) Eventually an arch will collapse, leaving only the end buttresses. Arches in all stages of development exist in Arches National Park, and several natural bridges share a Monument.

Capitol Reef	Buttes of Water-pocket Fold, an enormous wrinkle in the earth's crust, tower above a colored landscape. The massive 90-mile wall of ancient rock has slowly eroded into a vivid maze of cliffs, towers, domes, deep canyons, rock pinnacles and natural bridges.