Arches National Park - Geology

Arches National Park lies atop an underground salt bed called the “Paradox Formation” which is responsible for the arches, spires, balanced rocks, fins and eroded monoliths common throughout the park. Thousands of feet thick in places, the Paradox Formation was deposited over 300 million years ago when seas flowed into the region and eventually evaporated. Over millions of years, the salt bed was covered with the residue of floods and winds as the oceans returned and evaporated again and again. Much of this debris was cemented into rock. At one time this overlying layer of rock may have been more than a mile thick.

Salt under pressure is unstable, and the salt bed below Arches began to flow under the weight of the overlying sandstones. This movement caused the surface rock to buckle and shift, thrusting some sections upward into domes, dropping others into surrounding cavities, and causing vertical cracks which would later contribute to the development of arches.

As the subsurface movement of salt shaped the surface, erosion stripped away the younger rock layers. Water seeped into cracks and joints, washing away loose debris and eroding the "cement" that held the sandstone together, leaving a series of free-standing fins. During colder periods, ice formed, its expansion putting pressure on the rock, breaking off bits and pieces, and sometimes creating openings. Many damaged fins collapsed. Others, with the right degree of hardness and balance, have survived as the world famous formations of Arches National Park.

Faults deep in the Earth also contributed to the instability on the surface. The result of one such 2,500-foot displacement is called the Moab Fault and is visible from the Arches Visitor Center. Salt Valley was also formed by such a displacement. Except for isolated remnants, the major rock formations visible in the park today are the salmon-colored Entrada Sandstone, in which most of the arches form, and the tan-colored Navajo Sandstone.

Arches National Park - Wildlife

Though the natural quiet of Arches often creates the impression of lifelessness, many animals live here. Birds, lizards and some rodents are seen most frequently, though seasons and weather play a large role in determining what animals are active.

Desert animals have a variety of adaptations for dealing with the temperature and moisture stresses present in Arches. Most desert animals are nocturnal, being most active at night. This can be an adaptation to both predation and hot summer daytime temperatures. Mostly nocturnal animals include kangaroo rats, woodrats (also called packrats), and most other small desert rodents, skunks, ringtails, foxes, bobcats, mountain lions, bats and owls.

Animals that are most active at dawn and dusk are called “crepuscular.” These times of day are cooler than mid-day. The half-dark makes prey animals less visible, yet visibility is good enough to locate food. Some animals are crepuscular mostly because their prey is crepuscular. Crepuscular animals include mule deer, coyotes, porcupines, desert cottontails, black-tailed jackrabbits, and many songbirds.

A few desert animals are primarily active during the day, or “diurnal.” These include rock squirrels, antelope squirrels, chipmunks, lizards, snakes, hawks, and eagles. Many animals have a temperature range in which they are active, so alter their active times of day depending on the season. Snakes and lizards go into an inactive state of torpor during the winter, are active during the day during the late spring and early fall, and become crepuscular during the heat of summer. Many insects alter their times of activity. Mosquitoes, for example, may be out at night, at dawn, dusk or all day but not at night, depending on the temperatures.

MAMMALS

Almost 50 species of mammal are known to live in Arches. Some, like desert cottontails, kangaroo rats and mule deer, are common and may be seen by a majority of visitors. However, many desert animals are inactive during daylight hours or are wary of humans, so sightings can be truly special events. Tracks and scat are the most common signs of an animal’s presence.

Arches’ hot climate and lack of water favors small mammals. Because of their size, these animals are less able to migrate, but have an easier time finding shelter and require less food and water to live. Rodents are numerous: there are eleven species of mice and rats alone.

One animal uniquely adapted to life in the desert is the kangaroo rat. This rat lives its entire life consuming nothing but plant matter. Its body produces water by metabolizing the food it eats. However, even the kangaroo rat is prone to spending the hottest daylight hours sleeping in a cool underground burrow and may even plug the opening with dirt or debris for insulation.

Larger mammals, like mule deer and mountain lions, must cover more territory in order to find food and water, and sometimes migrate to nearby mountains during summer. In Utah, around 80% of a mountain lion’s diet consists of mule deer, so these animals are never far apart. However, unlike mule deer, mountain lion sightings are very rare.

Desert bighorn sheep live year-round in Arches, and are frequently sighted along Highway 191 south of the visitor center. These animals roam the talus slopes and side canyons near the Colorado River, foraging on plants and negotiating the steep, rocky terrain with the greatest of ease. Once in danger of becoming extinct, the desert bighorn are now making a tentative comeback that has been fueled by the healthy herds in nearby Canyonlands National Park.

REPTILES

Along with cacti and sand dunes, reptiles have become icons of the desert. The only reptiles found in Arches are snakes and lizards, underappreciated, sometimes feared, animals that play an important role in the high desert ecosystem. Lizards and snakes help control insect and rodent populations. In turn, both are potential meals for birds and mammals.

All reptiles are cold-blooded or, more accurately, “ectothermic,” regulating body temperature via external sources rather than internal metabolism. A reptile’s metabolic rate is very low, but so are its energy needs. Since keeping warm in the desert does not require much work, reptiles are well adapted to this environment. What energy they do generate can be used for reproduction and finding food instead of heating and cooling.

Of course, there are drawbacks to this lifestyle. Since they don’t pant or sweat, reptiles can’t endure extremely high temperatures without shade. Nor can they endure prolonged sub-zero temperatures. When it’s cold, reptiles hibernate or enter into an inactive torpor. Food stored as fat in their tails helps lizards survive these long periods of inactivity, so losing a tail can be life threatening.

If you visit Arches during the summer, you are sure to see lots of lizards. After birds, these reptiles are the most active animals once daytime temperatures reach 90 degrees and higher. They are usually visible sunbathing on rocks or chasing insects with their lightning-quick reflexes. Lizards found here include the northern whiptail, the desert spiny, and the colorful western collared lizard.

Most of the snakes found in Arches are harmless and nocturnal. All will escape from human confrontations given the opportunity. The midget-faded rattlesnake, a small subspecies of the western rattlesnake, has extremely toxic venom. However, full venom injections occur in only one third of all bites. The midget-faded rattlesnake lives in burrows and rock crevices and is mostly active at night.

AMPHIBIANS

Amphibians may be the last thing people think of when they visit Arches. However, the park is home to a variety of frogs and toads, as well as one species of salamander. Witnessing a chorus of toads may be one of the most memorable experiences canyon country has to offer. It is an awesome event that can fill a canyon with sound, sometimes for hours.

Amphibians are animals that have two life stages: a larval, aquatic form and an adult, terrestrial form. This is the difference between a tadpole and a frog. In Arches, amphibians lay their eggs in the potholes, springs and intermittent streams like Courthouse Wash.

Adult amphibians may wander away from water, but usually remain nearby and wait out dry periods in burrows. Breeding (and toad choruses) usually occurs on spring and summer nights after significant rainfall. Male frogs and toads do the vocalizing. Females lay long strings of gelatin-covered eggs which, depending on the species, may hatch within hours. Metamorphosis can take weeks, though the Great Basin spadefoot toad transforms to adulthood in as little as 14 days, the quickest of any amphibian.

BIRDS

Birds are the most visible animals in Arches. Even on the hottest summer day, turkey vultures and white-throated swifts circle above the rock formations. During winter, juncos and white-crowned sparrows forage around trees and shrubs. While Arches may not be considered a bird watching hot spot, 273 species have been seen in the park, including seasonal and year-round residents as well as migrants.

Arches owes much of this diversity to riparian corridors like Courthouse Wash and the Colorado River (which forms the park’s southern boundary). In the desert, animal life tends to concentrate around riparian areas because of the abundance of food, water and shelter. During spring and summer, mornings in these areas are filled with birdsong, including blue grosbeaks, yellow-breasted chats, spotted towhees and canyon wrens. Great blue herons may be seen hunting the shallows for fish, while cooper’s hawks deftly maneuver through the tangle of trees beyond the riverbanks.

Many birds favor the “upland” areas where grasses, shrubs and small trees dominate. Say’s phoebes, black-throated sparrows and western meadowlarks frequent grasslands. Pinyon jays, scrub jays, juniper titmice and black-throated gray warblers are usually seen in pinyon-juniper woodlands.

Since they are able to fly, it is difficult to generalize about what birds will be found in a particular habitat. However, regardless of habitat or season, the common raven figures prominently in the desert landscape. Ravens are intelligent birds that, according to scientists, display abilities to play and problem-solve rare among animals. This jet-black member of the crow family is also very vocal, using a variety of sounds for communication. Perhaps because of these qualities, ravens have achieved a certain stature in both European and Native American folklore.

Arches monitors bird populations at several selected locations in both upland and riparian areas. Some surveys count all birds, while others focus on birds that actually nest in the park. Findings from these surveys and others like them are used to monitor the health of local bird populations and estimate species richness throughout the country.

Arches National Park - Ecology

DESERTS

Arches lies near the heart of a desert called the “Colorado Plateau.” Deserts form when weather patterns or geographic land forms create an environment where lack of water limits biotic productivity. Water may exist in an unusable form such as ice, or may be absent altogether. There are four basic types of desert: high pressure, rain shadow, interior continental and coastal. High pressure deserts generally form at the middle latitudes (30 degrees) in each hemisphere where warm, dry air masses descend toward the earth's surface. Rain shadow deserts form in localized high pressure zones caused by warm, dry air descending from mountain ranges. The Colorado Plateau is also in the interior of a large continent, far away from significant water sources.

Because of the elevations throughout the region, with a mean of around 3,000 feet and peaks over 12,000 feet above sea level, the Colorado Plateau is also known as a cold or high desert. Though low humidity allows greater penetration of solar radiation, winter air temperatures frequently drop below freezing. In turn, summertime air and especially ground temperatures can reach levels lethal for many organisms. After sunset, the ground rapidly loses heat to the night sky and ambient air temperatures may drop significantly before dawn. Temperature fluctuations of over 40 degrees in a 24-hour period are not uncommon.

Arches receives more precipitation than many other deserts: about 9 inches annually. August is generally the wettest month, as weather systems from the southwest bring brief, intense tropical storms. However, precipitation is highly variable both temporally and spatially. During a single storm, one area may receive significantly more or less water than a neighboring spot less than a mile away.

SOIL COMPOSITION

Biological soil crust is a living groundcover that forms the foundation of high desert plant life in Arches and the surrounding area. This knobby, black crust is dominated by cyanobacteria, but also includes lichens, mosses, green algae, microfungi and bacteria.

Cyanobacteria, previously called blue-green algae, are one of the oldest known life forms. It is thought that these organisms were among the first land colonizers of the earth's early land masses, and played an integral role in the formation and stabilization of the earth's early soils. Extremely thick mats of these organisms converted the earth's original carbon dioxide-rich atmosphere into one rich in oxygen and capable of sustaining life.

When wet, Cyanobacteria move through the soil and bind rock or soil particles, forming an intricate web of fibers. In this way, loose soil particles are joined together, and an otherwise unstable surface becomes very resistant to both wind and water erosion. The soil-binding action is not dependent on the presence of living filaments. Layers of abandoned sheaths, built up over long periods of time, can still be found clinging tenaciously to soil particles, providing cohesion and stability in sandy soils at depths up to 10cm.

Nitrogen fixation is another significant capability of cyanobacteria. Vascular plants are unable to utilize nitrogen as it occurs in the atmosphere. Cyanobacteria are able to convert atmospheric nitrogen to a form plants can use. This is especially important in desert ecosystems, where nitrogen levels are low and often limiting to plant productivity.

Soil crusts have other functions as well, including an ability to intercept and store water, nutrients and organic matter that might otherwise be unavailable to plants.

EPHEMERAL POOLS

Throughout Arches, naturally occurring sandstone basins called "ephemeral pools" or "potholes" collect rain water and wind-blown sediment, forming tiny ecosystems where a fascinating collection of plants and animals have adapted to life in the desert. Potholes range from a few millimeters to a few meters in depth, and even the smallest potholes may harbor microscopic invertebrates.

To survive in a pothole, organisms must endure extreme fluctuations in several environmental factors. Surface temperatures vary from 140 degrees Fahrenheit in summer to below freezing in winter. As water evaporates, organisms must disperse to larger pools or tolerate dehydration and the drastic physical and chemical changes that accompany it.

The most extreme conditions exist when a pothole is dry. In addition to the wide temperature fluctuations, ultraviolet light from the sun can damage body tissues. Many aquatic organisms are adapted to acquiring oxygen through water and suffer when exposed to air. Pothole organisms have three main ways of dealing with drought.

"Drought escapers" are winged insects, amphibians and invertebrates that breed in potholes but cannot tolerate dehydration (e.g. mosquitoes, adult tadpole and fairy shrimp, spadefoot toads). In some cases, adults live in permanent water sources or on land and travel to temporary pools to mate and lay eggs. If the pool dries out before the young mature, they die. In the case of tadpole, fairy and clam shrimp, adults must lay their drought-tolerant eggs before the pool dries up.

"Drought resistors" (e.g. snails, mites) have a dormant stage resistant to drying out. These animals have a waterproof layer like a shell or exoskeleton that prevents body tissues from losing too much water while a pool is dry. By burrowing, these animals are able to seal themselves in the layers of fine mud that often coat the bottom of potholes and form an impermeable crust.

"Drought tolerators" (e.g. rotifers, tadpole and fairy shrimp eggs) are able to tolerate a loss of up to 92 percent of their total body water. This remarkable process, known as "cryptobiosis," is made even more remarkable by the fact that many cryptobiotic species can be rehydrated and become fully functional in as little as half an hour. Cryptobiosis is accomplished by a command center that remains hydrated while substituting sugar molecules for water throughout the rest of the body. This transfer maintains the structure and elasticity of an organism's cells during long periods of drought, and enables the organism to withstand the climatic extremes of the desert. In fact, brine shrimp have been hatched from cryptobiotic cysts that endured a flight on the outside of a spacecraft. Many tolerators have only one stage in their life cycle (e.g. egg, larva) that can survive desiccation, and will die if a pool dries up during another phase.

Pothole organisms not only have to endure dry spells, but also must evaluate conditions and decide when to break dormancy. Desert precipitation falls at irregular intervals, and once water enters a pothole there is no guarantee that there is enough for an organism to complete its life cycle. Most organisms living in potholes have very short life cycles, as brief as ten days, reducing the time water is required and allowing them to live in the shallow pools. Even vertebrates such as toads, which are found in other environments, display shorter development times when found in potholes.

However, the presence of water may not be the only cue used by eggs and dormant life forms to activate. Oxygen content, temperature, and other physical and chemical factors of the water may be evaluated. Some organisms produce different types of eggs that hatch on different cues; others lay eggs in different areas so that they experience slightly different environmental conditions. The net result is that not all eggs hatch at once and the species has a better chance of survival. After a pothole fills with water, the small ecosystem experiences many other changes. Water temperatures can be very high, while oxygen levels can be very low. As the pool shrinks from evaporation, its salinity increases and the pH changes. Many organisms are capable of surviving wide fluctuations in these factors, but for some these changes are an indication that the time for dormancy is near.

Arches National Park - Camping

The Devils Garden Campground is located eighteen miles from the park entrance and is open year-round. Facilities include potable water, picnic tables, grills, as well as both pit-style and flush toilets. There are no showers. Bring your own wood or charcoal for the grills. Some sites will accommodate RV's up to 30 feet in length.

Telephone and on-line reservations for both group and individual sites may be made through www.recreation.gov. Reservations are not accepted by the park, and the park does not maintain information about site availability.

Individual Sites

The campground has 52 individual sites which are $15 per night and will accommodate up to ten people. Up to 28 of the individual sites may be reserved for nights between March 1st and October 31st. Reservations must be made no less than 4 days and no more than 240 days in advance. There is an additional $9 booking fee for reservations. To make a reservation, visit www.recreation.gov, or call (877) 444-6777, (877) 833-6777 (TDD), or (518) 885-3639.

The remaining 24 campsites are available on a first-come, first-served basis each day beginning at 7:30 a.m. at the park entrance station or visitor center.

Group Sites

The campground has two sites for groups of eleven or more people. The Juniper Basin campsite will accommodate up to 55 people; the Canyon Wren campsite up to 35. The group camping fee is $3 per person per night, with a $33 per night minimum. No recreational vehicles or trailers are permitted in the group sites.

Group campsites may be reserved year-round. Reservations must be made no less than 4 days and no more than 360 days in advance. There is an additional $9 booking fee for reservations. To make a reservation, visit www.recreation.gov, or call (877) 444-6777, (877) 833-6777 (TDD), or (518) 885-3639.

Unreserved group campsites are available on a first-come, first-served basis on the day of arrival.

Backcountry Camping and Backpacking

Arches is a relatively small park, with very few areas far enough from roads to qualify as backcountry. Outside the developed areas there are no designated trails, campsites, or reliable water sources.

In order to backpack in Arches, you must obtain a free backcountry permit at the visitor center. The maximum group size is twelve, but smaller groups are strongly recommended to reduce impacts. Permits may not be reserved in advance.

Backpackers should know how to navigate with a topographic map, recognize safety hazards and practice low-impact camping specific to the high desert. Primary safety considerations include steep terrain, loose rock, lightning, flash floods, and dehydration.


Other Camping Options

The Bureau of Land Management (BLM) operates many campgrounds in the Moab area. Some accommodate large groups and may be reserved in advance. For more information, visit the BLM's Moab Field Office website.

Arches National Park - Contact

Arches National Park
PO Box 907
Moab, UT 84532-0907

Visitor Information: (435) 719-2299
Headquarters: (435) 719-2100
By Fax: (435) 719-2305

The Arches National Park Visitor Center is located just after the entrance to the park. The visitor center is open daily during the following hours:

April through October: 7:30 a.m. to 6:30 p.m.
November through March: 8:00 a.m. to 4:30 p.m.

The visitor center is closed only on December 25th.