Arches National Park

Arches National Park protects the greatest concentration of natural sandstone arches anywhere on earth. Like many other parks on the Colorado Plateau, eroded sandstone provides the palette for sensational and colorful desert vistas. But special geological circumstances millions of years old, have made Arches unique among the breath-taking assets of the Great Basin Desert.

Native Peoples

Paleo-Indians occupied the area of Arches National Park from 12,000 to 9,500 years ago hunting large game such as mammoth, bison and sloths. They were attracted to the area around Delicate Arch by the concentration of chalcedony, a variety of quartz that can be chipped to make a sharp edge. As temperatures warmed and the megafauna retreated to cooler regions about 9,000 years ago, archaic hunter-gathers occupied the area, but left only scant pictographs like those in Barrier Canyon as evidence.

By about 2,000 years ago, the Arches region was a frontier between the agricultural cultures of the Anasazi and Fremont peoples, but neither occupied the area continuously. By about 1300, both cultures moved further south and were replaced by the Utes and Paiutes, who occupied the area when Europeans first entered the area.

Exploration & Settlement

Although Spanish explorers twice came as close as the Colorado River across from Arches National Park in the 1500s and 1700s, it wasn't until 1844 that mountain man Denis Julien first recorded his entrance into the area. Mormon missionaries established Elk Mountain Mission near the town of Moab in 1855, but abandoned the effort after Utes killed three settlers.

In 1888, Civil War veteran John Wesley Wolf and his son Fred established the Bar-DX, a 150-acre ranch along Salt Wash, within a mile of Delicate Arch. After two lonely decades, the Wolfe family returned to Ohio in 1920. The ranch changed hands a number of times, until the property was sold to the federal government and incorporated into the national park. A weathered log cabin, root cellar and corral remain as evidence of these early ranchers.

Park History

In the 1920s, Utah prospector Alexander Ringhoffer, after traveling through Klondike Bluffs on the western edge of Salt Valley, contacted railroad executives of the D&RGW to share the splendor of the place. They were so impressed with the breathtaking vistas, they contacted in turn Stephen T. Mather, first director of the National Park Service, who pushed for creation of a national monument, which President Herbert Hoover proclaimed in 1929. It's size was altered by various Presidents through the years until it was declared a national park by an act of congress in 1971.

Natural History

Plants & Animals

Although Arches is in the Great Basin Desert, it is a cool desert and a high one. The most common plant community here s a pygmy forest of Juniper and Pinion Pine, which covers 40 percent of the park. More than 350 other plant species thrive here as well, including yuccas, Blackbrush, Indian Paintbrush, Dropseed, Indian Ricegrass, Prickly Pear Cactus, Rockrose and Mormon Tea. A diverse profusion of wildflowers also bloom from April through June including Larkspur, Prince's Plum, Peppergrass, Mule-ears and Columbine. Willows and non-native Tamarisk line the riverbanks and narrow floodplains.

Most species of mammals are nocturnal in Arches, but you might also see Mule Deer, Kit Fox, Jackrabbits, Desert Cottontails and Kangaroo Rats. The Western Rattlesnake, Collared Lizard, Red-spotted Toad and Tadpole Shrimp are also common.

Geology

Arches National Park lies over a deeper part of the Paradox Basin where a landlocked arm of an ancient sea accumulated salt and interspersed mineral deposits for millions of years, beginning about 400 million years ago. The later overburden of materials on the salt beds caused the rock salt to flow plastically, pushing upward through fault lines to form salt anticlines. Later water erosion caused collapse, creating sunken valleys and escarpments.

Massive beds Entrada sandstone, where most of the arches occur, were deposited about 200 million years ago in the form of dunes. This type of sandstone is especially susceptible to exfoliation (peeling off from bedrock,of concentric rock slabs) The upwarping of these beds, caused by the upwelling of the salt anticlines below, causes deep, parallel, vertical fissures to occur, exposing the rock to the elements.

As the weathering and erosion enlarges the cracks and fractures, narrow sandstone walls called fins develop about 20 feet apart. Frost action, exfoliation and crumbling then rounds off the tops of the fins. The process of exfoliation, due to water, ice and wind working on both sides of the fin, eventually breaches the rock causing windows. Rockfalls, continued erosion at ground level where water collects and wind erosion eventually enlarge and perforate the windows causing arches, which eventually collapse altogether.

Click here to see a video
about the geologic process that created the arches

Landscape Arch
Most of the arches in the park are in Devils Garden, which has them in all phases of development. Landscape Arch, billed as the longest in the world, is 291 feet long and 105 feet high. At one portion of the arch, it is only 6 feet wide, indicating that it is about at the end of its geologic life before collapsing. It may have taken 100,000 years to create this spectacular wonder.

Balanced Rock

Balanced Rock
Near The Windows, about midway into the park, Balanced Rock offers a great example of the geologic feature called a hoodoo. It is formed by wind erosion, as well as erosion by water seepage. A resistant block of Slickrock Sandstone (from the Entrada layer) is balanced on a softer layer of Dewey Bridge Beds, which in turn rests on a Navajo Sandstone base. The huge cap rock weights 3500 tons and stands 55 feet high.