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Arches National Park

Utah · Established November 12, 1971

Stone windows and balanced fins above a buried sea of salt

Area: 76,679 acres
Established: November 12, 1971
Recreation visits: 1,511,740 / yr
State: Utah
Highest point: Elephant Butte, 5,653 ft (1,723 m)
Lowest point: About 4,085 ft (1,245 m), near the visitor center

Arches Weather Forecast

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Seven-day outlook at the park's reference point (38.723, -109.586). Elevation changes everything in the mountains — expect colder, windier and wetter conditions on high ground.

Map of Arches National Park

The Park

Just north of Moab, Utah, Arches National Park packs the densest collection of natural stone arches on Earth into a compact slice of the Colorado Plateau. Salmon-red fins, balanced rocks, spires and windows stand above slickrock basins and juniper flats, with the snow-capped La Sal Mountains floating on the eastern horizon.

First protected as a national monument in April 1929 and made a national park on November 12, 1971, Arches covers about 76,679 acres (310.3 sq km) and welcomes roughly 1.5 million visits a year. It is a high desert of big daily temperature swings, fierce summer sun, sudden thunderstorms and crisp, star-filled nights.

Geography

The park sits on a high desert plateau between roughly 4,000 and 5,650 feet, bordered on the south by the Colorado River corridor near Moab. Its terrain is a patchwork of open sandy flats, sheer-walled fins, deep washes and long, collapsed valleys.

The main road climbs from the visitor center past the monoliths of Park Avenue and Courthouse Towers, then runs north to the Windows Section, the maze of fins called the Fiery Furnace, the broad trough of Salt Valley and finally Devils Garden at road's end, where Landscape Arch and dozens of other spans hide among the fins. Delicate Arch stands alone on a slickrock bowl east of Salt Wash.

Elephant Butte, near the Windows, is the park's high point. Courthouse Wash and Salt Wash drain the park toward the Colorado River, running only after rain.

Landmarks

Delicate ArchArchA freestanding arch of Entrada Sandstone on the rim of a slickrock bowl, symbol of Utah.
Landscape ArchArchAn impossibly thin ribbon of rock in Devils Garden, among the longest natural spans in the world.
Double ArchArchTwo arches sharing a common footing, carved largely from above by water pooling in a pothole.
North WindowArchOne of the paired Windows, large openings in a single fin in the Windows Section.
Turret ArchArchAn arch capped by a stout tower, facing the Windows across the trail.
Elephant ButtePeak · 5,653 ftThe highest point in the park, a sandstone butte rising above the Windows Section.
Balanced RockAreaA massive boulder of Entrada Sandstone perched on a pedestal of softer mudstone.
Park AvenueCanyonA corridor of sheer sandstone walls that early visitors likened to a city skyline.
Courthouse TowersAreaA cluster of tall monoliths including the Three Gossips and Sheep Rock.
Petrified DunesDuneRounded mounds of Navajo Sandstone preserving the shapes of ancient wind-blown dunes.
Fiery FurnaceAreaA labyrinth of narrow fins and passageways that glows red at sunset.
Salt ValleyValleyA long trough formed where a buried salt dome dissolved and the overlying rock collapsed.
Wolfe RanchAreaA homesteader's cabin at the start of the trail to Delicate Arch, beside Salt Wash.
Skyline ArchArchA roadside arch whose opening doubled in size when a large block fell out in 1940.
Double O ArchArchTwo stacked openings in a fin deep in Devils Garden.
Tower ArchArchA remote arch beside a sandstone tower in the Klondike Bluffs area.

Geology

The secret of Arches lies underground. Around 300 million years ago, during the Pennsylvanian Period, an arm of the sea repeatedly flooded and evaporated in a sinking region called the Paradox Basin. It left behind a salt bed thousands of feet thick, the Paradox Formation.

Over the next 150 million years, rivers, tidal flats and immense deserts buried the salt under layer after layer of sediment. Among them were the buff-colored Navajo Sandstone, the fossil dunes of an Early Jurassic sand sea, and above it the salmon-colored Entrada Sandstone, in which nearly all of the park's arches are carved. Thousands of feet of younger rock, including the marine Mancos Shale, once covered them.

Salt behaves like slow-moving putty under pressure. As the weight of the overlying rock pressed down, the salt flowed and bulged upward into long ridges, arching the sandstone above and cracking it into parallel joints. Later, when groundwater dissolved the tops of the salt ridges, the rock above them sagged and collapsed, creating Salt Valley and Cache Valley and leaving the flanking sandstone fractured into countless thin, vertical slabs.

Once regional uplift and erosion stripped away the younger cover, water went to work on those fractured slabs. Rain seeped into cracks, froze and expanded; dissolved the natural cement that holds sand grains together; and washed loosened grains away. The joints widened into slots, the slabs became freestanding fins, and where a weakness ran through a fin, a hole opened and grew into an arch. The process continues: Wall Arch collapsed in 2008, and every arch standing today will eventually fall as new ones form.

Deep time

About 300 million years agoRepeated evaporation of seawater in the Paradox Basin deposits a thick bed of salt and gypsum.
Permian to TriassicRivers and floodplains bury the salt under red beds, and the growing load begins to squeeze the salt into underground ridges.
About 200 million years agoA vast Early Jurassic sand sea lays down the dunes that become the Navajo Sandstone.
Middle JurassicCoastal dunes, tidal flats and streams deposit the Entrada Sandstone, the rock that will host the arches.
CretaceousAn inland sea spreads across the region and deposits the Mancos Shale, part of thousands of feet of younger cover.
Last several million yearsUplift of the Colorado Plateau accelerates erosion, stripping the cover rocks and exposing the fractured sandstone.
OngoingSalt dissolution, frost, rain and gravity carve fins into arches and topple old ones, as when Wall Arch fell in 2008.

The rocks

Paradox FormationPennsylvanian
Thick salt and gypsum beds whose flow and dissolution set the stage for the park's fins and valleys.
Honaker Trail FormationPennsylvanian
Marine limestones, sandstones and shales deposited above the salt.
Moenkopi FormationTriassic
Chocolate-brown mudstones and siltstones of ancient tidal flats.
Chinle FormationLate Triassic
Colorful river and floodplain deposits that form slopes below the cliffs.
Wingate SandstoneLate Triassic
Cliff-forming, wind-deposited sandstone seen in canyon walls near the park entrance.
Navajo SandstoneEarly Jurassic
Buff, cross-bedded fossil dunes that form the Petrified Dunes and many domes.
Entrada SandstoneMiddle Jurassic
Salmon-red sandstone with the Dewey Bridge, Slick Rock and Moab members, home to nearly all the arches.
Morrison FormationLate Jurassic
Varicolored river and lake deposits exposed along parts of Salt Valley.
Mancos ShaleCretaceous
Gray marine shale surviving only as isolated remnants in the park.

Trees, Plants & Ecosystems

499vascular plant species recorded

Pinyon-juniper woodlandRocky soils and fractured bedrock throughout the park
The dominant plant community, with twisted Utah junipers and pinyon pines growing from cracks and thin soils.
Desert shrublandShallow sandy soils, about 4,000 to 5,200 ft
Blackbrush, Mormon tea and purple sage spread across sandy benches; greasewood and saltbush mark alkaline ground.
Desert grasslandDeeper soils on flats
Bunchgrasses such as Indian ricegrass and galleta grow among patches of dark biological soil crust.
Washes, seeps and riparian corridorsCourthouse Wash, Salt Wash and shaded alcoves
Cottonwoods and willows follow the water table, while monkeyflowers, columbines and maidenhair fern cling to dripping springs.
Slickrock and potholesExposed sandstone
Bare rock collects rainwater in potholes that briefly teem with tiny aquatic life.

Trees

Utah juniperJuniperus osteospermaThe most common tree in the park, able to shut off water to whole branches during drought.
Two-needle pinyonPinus edulisA slow-growing nut pine that pairs with juniper across rocky ground.
Rocky Mountain juniperJuniperus scopulorumA less common juniper of cooler, more sheltered sites.
Fremont cottonwoodPopulus fremontiiA broad shade tree that grows only where its roots reach groundwater along washes.
Netleaf hackberryCeltis reticulataA drought-tolerant tree of canyon bottoms with small, bird-favored berries.
Singleleaf ashFraxinus anomalaA small, shrubby ash of rocky slopes and alcoves.
Gambel oakQuercus gambeliiForms small thickets in moist, protected spots.
Five-stamen tamariskTamarix chinensisAn invasive shrub-tree from Eurasia that lines waterways of the Colorado River system.

Wildflowers, shrubs & other plants

BlackbrushColeogyne ramosissimaA dark, spiny shrub that dominates vast stretches of shallow sandy soil.
Mormon teaEphedra viridisA leafless, green-stemmed shrub whose jointed twigs were brewed into tea by settlers.
Sacred daturaDatura wrightiiProduces the largest flowers in canyon country, huge white trumpets that open at night.
Harriman's yuccaYucca harrimaniaeA low yucca with stiff, curling leaves and creamy spring flower stalks.
Plains pricklypearOpuntia polyacanthaA common cactus with flat pads and yellow to pink spring blossoms.
Claret cup cactusEchinocereus triglochidiatusMounded clumps that burst into scarlet flowers in spring.
Small-flower fishhook cactusSclerocactus whippleiA small barrel cactus with hooked spines, one of the park's less common succulents.
Wyoming paintbrushCastilleja linariifoliaA red-orange wildflower that taps nutrients from the roots of neighboring shrubs.
Small-leaf globemallowSphaeralcea parvifoliaAn apricot-orange mallow that blooms along roads and trails.
Yellow beeplantCleome luteaA tall, yellow-flowered annual that can explode into bloom after good rains.
Purple sagePoliomintha incanaA fragrant, silvery shrub of sandy soils with lavender flowers.
Indian ricegrassStipa hymenoidesA graceful bunchgrass whose seeds were an important food for native peoples.
Alcove columbineAquilegia micranthaA delicate columbine of shaded seeps and hanging gardens.
Southern maidenhair fernAdiantum capillus-venerisA lacy fern that grows where water drips from sandstone alcoves.

Wildlife

44mammals
182birds
14reptiles
5amphibians
10fish

Mammals

Mule deerOdocoileus hemionusThe largest commonly seen mammal, most active at dawn and dusk.
Bighorn sheepOvis canadensisDesert bighorn sometimes appear on cliffs near the Colorado River and the park entrance.
CoyoteCanis latransFrequently heard yipping at night across the flats.
Kit foxVulpes macrotisA small, big-eared desert fox that hunts rodents by night.
Gray foxUrocyon cinereoargenteusA fox that can climb trees, living among rocks and junipers.
RingtailBassariscus astutusA nocturnal, cat-sized relative of the raccoon with a banded tail.
BobcatLynx rufusAn elusive predator of rocky terrain.
Mountain lionPuma concolorPresent but rarely seen, following deer through the park.
Rock squirrelOtospermophilus variegatusA large, bushy-tailed ground squirrel of boulders and ledges.
White-tailed antelope squirrelAmmospermophilus leucurusDashes across hot flats with its white tail curled over its back.
Ord's kangaroo ratDipodomys ordiiHops on long hind legs and can survive without ever drinking water.
Desert woodratNeotoma lepidaBuilds middens of sticks and debris in rock crevices that can persist for thousands of years.
Desert cottontailSylvilagus auduboniiCommon around shrubs at dawn and dusk.
Canyon batParastrellus hesperusA tiny bat often seen flitting over washes at dusk.

Birds

Common ravenCorvus coraxClever, acrobatic and ever-present around viewpoints.
Woodhouse's scrub-jayAphelocoma woodhouseiiA noisy blue jay of the pinyon-juniper woodland.
Pinyon jayGymnorhinus cyanocephalusTravels in large, chattering flocks and plants pinyon seeds it forgets to recover.
Canyon wrenCatherpes mexicanusIts cascading, descending song echoes off sandstone walls.
Rock wrenSalpinctes obsoletusBobs on boulders and slickrock, probing crevices for insects.
White-throated swiftAeronautes saxatalisRockets past cliffs and fins at astonishing speed.
Peregrine falconFalco peregrinusNests on high cliffs in and around the park.
Red-tailed hawkButeo jamaicensisSoars over the flats hunting rodents and rabbits.
Golden eagleAquila chrysaetosA powerful raptor occasionally seen riding thermals above the fins.
Say's phoebeSayornis sayaA rusty-bellied flycatcher that often nests on ledges and buildings.
Juniper titmouseBaeolophus ridgwayiA plain gray, crested bird tied closely to juniper woodland.
Violet-green swallowTachycineta thalassinaNests in cliff crevices and hawks insects above the rocks.
Black-throated sparrowAmphispiza bilineataA handsome desert sparrow with a bold black bib, singing from shrubs.
Mountain bluebirdSialia currucoidesBrilliant sky-blue flocks move through open country in winter and spring.

Reptiles & amphibians

Eastern collared lizardCrotaphytus collarisA big-headed lizard with a black collar that can sprint on its hind legs.
Side-blotched lizardUta stansburianaOne of the most common lizards on trails and rocks.
Plateau lizardSceloporus tristichusA spiny lizard often seen doing push-up displays on boulders.
Tiger whiptailAspidoscelis tigrisA restless, long-tailed lizard constantly foraging among shrubs.
Midget faded rattlesnakeCrotalus oreganusA pale, small rattlesnake subspecies of the canyon country; give it space.
GophersnakePituophis cateniferA large, harmless constrictor that hisses and mimics a rattlesnake when threatened.
Great Basin spadefootSpea intermontanaEmerges after summer rains to breed in temporary pools and potholes.
Red-spotted toadAnaxyrus punctatusA small, flattened toad of rocky washes and seeps.

Fish

Flannelmouth suckerCatostomus latipinnisA native Colorado River basin sucker found in the river along the park's edge.
Bluehead suckerPantosteus discobolusA native fish that scrapes algae from rocks in flowing water.
Speckled daceRhinichthys osculusA small native minnow of streams and springs.

Species totals are the park's certified NPSpecies checklist (occurrence: present).

Climate & When to Visit

Arches lies in the high desert of the Colorado Plateau, where thin, dry air lets temperatures swing dramatically, sometimes more than 40 degrees F between dawn and afternoon. Annual rainfall is scant, and much of it arrives in two pulses: winter storms and the late-summer monsoon.

Spring and fall are the gentle seasons, with daytime highs around 60 to 80 F and lows of 30 to 50 F. Summer afternoons regularly top 100 F, and July through September bring bursts of thunderstorms that can dump heavy rain on bare rock and send flash floods down washes. Winters are cold and mostly dry, with highs of 30 to 50 F, lows that can drop to single digits, and occasional snow that dusts the red rock.

Spring
Mild and popular, with highs of 60 to 80 F, cool nights, gusty winds and wildflowers from April into May.
Summer
Hot and intensely sunny, often over 100 F; hike at dawn, carry plenty of water and watch for afternoon monsoon storms.
Autumn
Mid-September through October brings comfortable highs of 60 to 80 F, clear skies and golden cottonwoods in the washes.
Winter
Cold and quiet, with highs of 30 to 50 F, lows from about 0 to 20 F, icy trails and occasional snow on the arches.

Weather hazards

Extreme heat: Summer temperatures above 100 F and little shade make dehydration and heat illness real risks; carry at least a gallon of water per person per day.
Flash floods: Monsoon storms can send sudden torrents through washes and the Fiery Furnace; avoid narrow canyons when storms threaten, even if skies overhead are clear.
Lightning: Exposed slickrock and viewpoints like Delicate Arch offer no shelter; retreat to a vehicle when thunder is heard.
Slippery and icy slickrock: Sandstone becomes slick when wet, and winter ice lingers on shaded trail sections.
Rockfall: Arches and fins shed rock without warning; stay on trails and do not climb on arches.

Arches Questions

When is the best time to visit Arches National Park?

April through May and mid-September through October offer the most comfortable weather, with highs in the 60s to 80s F. These are also the busiest months, so arrive early and check whether a timed-entry reservation is required. Winter is quiet and often beautiful but cold.

How hot does Arches get in summer?

Summer highs regularly exceed 100 F, and exposed rock radiates heat long after sunset. Start hikes like Delicate Arch at sunrise, carry ample water, and be alert for afternoon thunderstorms from July into September.

How were the arches formed?

A thick salt layer buried deep beneath the park flowed and dissolved over millions of years, cracking the overlying Entrada Sandstone into parallel fins. Water, frost and gravity then enlarged weaknesses in those fins until openings broke through and grew into arches.

How many arches are in Arches National Park?

More than 2,000 natural arches have been documented, the highest concentration anywhere. To count, an opening must be at least 3 feet across in any direction.

What wildlife can I see at Arches?

Lizards, ravens, scrub-jays and ground squirrels are easy to spot by day, while mule deer appear at dawn and dusk. Most mammals, including kit foxes, ringtails and kangaroo rats, are nocturnal, and desert bighorn sheep occasionally show up near the entrance and Colorado River.

Will Delicate Arch fall?

Eventually, yes. All arches are temporary: Wall Arch collapsed in 2008, and large slabs have fallen from Landscape Arch. Erosion is slow on a human timescale, but every arch in the park is on its way to becoming a pile of sand.

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Sources: www.nps.gov · www.nps.gov · www.nps.gov · www.nps.gov · irmaservices.nps.gov · en.wikipedia.org · en.wikipedia.org · Official NPS site