Arches National Park is a national park in the United States located in eastern Utah. It is near the Colorado River, 4 miles (6 kilometers) north of Moab, Utah. The park has more than 2,000 natural sandstone arches, including the famous Delicate Arch, which is the highest concentration of natural arches in the world. It also has many other unique geological features, such as spires, balanced rocks, sandstone fins, and eroded monoliths. These formations are created because the park lies above an underground salt layer.

The park covers an area of 310.31 km (76,680 acres; 119.81 square miles; 31,031 hectares) of high desert on the Colorado Plateau. The highest point in the park is 5,653 feet (1,723 meters) at Elephant Butte, and the lowest point is 4,085 feet (1,245 meters) at the visitor center. The park receives less than 10 inches (250 millimeters) of rain each year on average.

The National Park Service manages the area. It was first established as a national monument on April 12, 1929, and later became a national park on November 12, 1971. In 2021, the park had more than 1.8 million visitors. Visitor numbers decreased in recent years, with about 1.5 million visitors in 2024.

Geology

Arches National Park is located above a thick underground salt layer, which helped form the park's arches, spires, balanced rocks, and sandstone fins. This salt layer was deposited in the Paradox Basin of the Colorado Plateau about 300 million years ago when a sea covered the area and later dried up. Over millions of years, layers of rock and soil from the nearby Uncompahgre Uplift were deposited on top of the salt. During the Early Jurassic period, around 200 million years ago, desert conditions caused the Navajo Sandstone to form. Later, around 140 million years ago, the Entrada Sandstone was deposited on top of the Navajo. Over time, more than 5,000 feet of rock layers were added to the area, but most of them have since been eroded. Some older layers, like the Cretaceous Mancos Shale, remain visible in the park. Most of the park's arches are found in the Entrada Sandstone.

The weight of the rock layers above the salt caused the salt to melt and push upward, forming salt domes. These movements also created unusual salt ridges and caused parts of the rock to break and sink between the domes. One example of this movement is the Moab Fault, which is visible from the visitor center.

As salt moved underground, erosion removed the younger rock layers from the surface. Today, the main rock layers visible in the park are the salmon-colored Entrada Sandstone, where most arches form, and the buff-colored Navajo Sandstone. These layers are stacked like cake layers across the park. Over time, water seeped into cracks and joints in the rock. Ice formed in these cracks, expanding and breaking the rock apart. Wind then removed loose pieces, leaving behind tall, thin rock walls called fins. Wind and water continued to erode these fins, weakening the rock until pieces broke off. Some fins collapsed, but others remained standing, forming the famous arches.

Although the park's landscape appears strong, it is very fragile. Over 1 million visitors each year damage the soil, which is covered in a thin layer of living organisms like cyanobacteria, algae, fungi, and lichens. The park's dry climate, limited rainfall, and lack of plant cover make its soil weak and slow to recover from foot traffic. Scientists study soil damage using methods like the cytophobic soil crust index, water infiltration tests, and t-tests that compare undisturbed and disturbed areas.

A salt layer formed 300 million years ago now lies beneath the park. Over time, this salt was covered by sediments that hardened into rock layers, including the Entrada Sandstone. Rock layers around the salt continued to erode, forming vertical walls called fins. Sand trapped between these fins mixed with slightly acidic rain and carbon dioxide to create carbonic acid, which dissolved the calcium carbonate holding the sandstone together. Weaker layers of rock at the bottom of the fins eroded first, creating openings. Gravity caused the stronger rock above to fall into an arch shape. Arches form where the rock is most fractured or weak. Water, wind, and time continue to erode the area, creating new arches over thousands of years. All arches in the park are made of Entrada Sandstone, which is divided into three groups: Slick rock, Dewey rock, and Moab members. Vertical arches can form from Slick rock, a mix of Slick rock and Moab, or Slick rock resting above Dewey rock. Horizontal arches, also called potholes, form when vertical and horizontal caves join together. Erosion will continue, causing some arches to collapse, but new ones will form for thousands of years.

According to the Köppen climate classification system, the Arches Visitor Center has a cold semi-arid climate (BSk).

Plants and animals

Many types of animals live in Arches National Park, such as spadefoot toads, antelope squirrels, scrub jays, peregrine falcons, several kinds of sparrows, red foxes, desert bighorn sheep, kangaroo rats, mule deer, cougars, midget faded rattlesnakes, yucca moths, western rattlesnakes, and collared lizards.

Many plant species grow in the park, including prickly pear cactus, Indian ricegrass, bunch grasses, cheatgrass, moss, liverworts, Utah juniper, Mormon tea, blackbrush, cliffrose, four-winged saltbrush, pinyon pine, evening primrose, sand verbena, yucca, and sacred datura.

A type of soil crust made up of cyanobacteria, lichen, mosses, green algae, and microfungi is found throughout southeastern Utah. The thread-like growths help hold soil particles together, forming a layer that is more likely to resist erosion. This living soil layer absorbs and stores water easily, which allows more complex plants to grow in areas with little rainfall.

History

People have lived in this area since the end of the last ice age, about 10,000 years ago. The Fremont people and Ancestral Puebloans lived there until about 700 years ago. In 1775, Spanish missionaries met the Ute and Paiute tribes in the area. The first European-Americans to try to settle there were the Mormon Elk Mountain Mission in 1855, but they left soon after. Later, in the late 1870s, ranchers, farmers, and people looking for resources settled in Moab and the nearby Riverine Valley. People began to talk about the beauty of the area's rock formations as a possible place for tourists to visit.

The Arches area was first brought to the attention of the National Park Service by Frank A. Wadleigh, a passenger traffic manager for the Denver and Rio Grande Western Railroad. In September 1923, Wadleigh and railroad photographer George L. Beam visited the area at the invitation of Alexander Ringhoffer, a Hungarian-born prospector living in Salt Valley. Ringhoffer had discovered a scenic area with his family the year before and called it Devils Garden (now known as Klondike Bluffs). Wadleigh was impressed and suggested to National Park Service director Stephen T. Mather that the area be made a national monument.

The next year, Laurence Gould, a University of Michigan student studying the geology of the nearby La Sal Mountains, saw the area with local doctor Dr. J. W. "Doc" Williams and supported the monument idea. Government investigators later examined the area, but confusion about its exact location led to changes in its name. The name Devils Garden was moved to an area on the opposite side of Salt Valley that includes Landscape Arch, the longest arch in the park. Ringhoffer's original discovery was not included, but another nearby area called the Windows was added. In 1926, the National Park Service supported making the area a monument, but President Calvin Coolidge's Interior Secretary, Hubert Work, opposed it. In April 1929, President Herbert Hoover signed a proclamation to create Arches National Monument, which included two small, separate sections. The purpose of the reservation, under the 1906 Antiquities Act, was to protect the arches, spires, balanced rocks, and other sandstone formations for their scientific and educational value. The name "Arches" was suggested by Frank Pinkely, a Park Service superintendent, after he visited the Windows section in 1925.

In late 1938, President Franklin D. Roosevelt signed a proclamation to expand the monument to protect more scenic features and allow for tourism facilities. A small change was made in 1960 by President Dwight Eisenhower to adjust a road route.

In early 1969, President Lyndon B. Johnson signed a proclamation to greatly expand the monument. Two years later, President Richard Nixon signed a law passed by Congress that reduced the area but changed its status. Arches National Park was officially dedicated in May 1972.

In 1980, vandals tried to use a strong kitchen cleaner to damage ancient petroglyphs in the park. Park officials asked physicist John F. Asmus, who used lasers to restore art, to repair the damage. Asmus used intense light to remove most of the cleaner. In 2016, vandals carved out part of a rock on Frame Arch. In 2018, the arch was repaired using color matching and modern filling methods.

Recreational activities

Climbing Balanced Rock or any arch in Arches National Park that has an opening larger than 3 feet (0.9 meters) is not allowed according to park rules. Climbing on other features in the park is permitted but must follow specific guidelines. Additionally, slacklining and BASE jumping are not allowed anywhere in the park.

Climbing on named arches had been banned for a long time, but after Dean Potter completed a free climb on Delicate Arch in May 2006, the park's legal team said the rules were unclear and hard to enforce. In response, the park updated its rules later that month. The current ban on climbing arches was finally put in place in 2014.

Approved activities in the park include driving on roads, hiking, bicycling, camping at Devils Garden campground, backpacking, canyoneering, and rock climbing. Permits are required for rock climbing, canyoneering, and backpacking. Guided tours and ranger-led programs are also available.

Astronomy is a popular activity in the park because of its dark skies. However, more light from nearby towns, such as Moab, has increased light pollution.

Publicity

Delicate Arch is featured on the third quarter released in 2014 as part of the U.S. Mint's America the Beautiful Quarters program, which honors national parks and historic sites. The Arches quarter was the most produced of the five 2014 national park quarters, with over 465 million coins made.

Edward Abbey, an American writer, worked as a park ranger at Arches National Monument in 1956 and 1957. He wrote a book called Desert Solitaire based on his experiences and journal entries from that time. The popularity of Abbey's book, along with growing interest in outdoor adventure activities, has increased the number of visitors to the area. Permitted activities in the park include camping, hiking on marked trails, backpacking, hiking in canyons, rock climbing, bicycling, and driving on existing roads, both paved and unpaved. The Hayduke Trail, a long backpacking route named after a character from Abbey's book, starts within the park.

Features

• Argon Tower – a 260-foot-tall pillar located on Park Avenue
• Balanced Rock – a large rock that balances on a narrow base, about the size of three school buses
• Courthouse Towers – a group of tall stone columns
• Dark Angel – a freestanding 150-foot-tall (46 meters) sandstone pillar at the end of the Devils Garden Trail
• Delicate Arch – a single arch that is a symbol of Utah and the most well-known arch in the park
• Devils Garden – many arches and columns found along a ridge
• Double Arch – two arches that share one end
• Fiery Furnace – an area with narrow, maze-like paths and tall rock columns (see biblical reference, Book of Daniel, chapter 3)
• Landscape Arch – an extremely thin and long arch in the Devils Garden that spans 290 feet (88 meters), the longest arch in the park
• Marching Men – a group of pillars located along Park Avenue in Arches National Park
• Petrified Dunes – fossilized remains of dunes that were once blown from ancient lakes covering the area
• Queen Nefertiti Rock – a rock formation located on Park Avenue
• Queen Victoria Rock – a rock formation located on Park Avenue
• Sheep Rock – a rock formation located north of Park Avenue
• The Organ – a butte that rises above the park road
• The Phallus – a rock spire that resembles a phallus
• Three Penguins – a rock formation near the park entrance
• Tower of Babel – a rock formation that rises above the park road
• Wall Arch – located along the popular Devils Garden Trail; collapsed on August 4 or 5, 2008
• The Three Gossips – a medium-sized sandstone tower located in the Courthouse Towers area.