Arches National Park Geology

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Geology

76,359 acres full of  awe inspiring formations along with cryptobiotic soil, ephemera pools, dry arroyos and large expanses of mixed grassland make Arches National Park a geological wonderland.

  • The Dark Angel is a 150 foot monolith in the Devil's Garden.
  • Cryptobiotic soil takes 100 years to form and can be killed by a footstep.
  • Landscape Arch has a span loner than a football field.
  • Natural arches are chiseled by wind and water. 
  • Since 1970, 43 arches have collapsed.

A Geology Lesson

The park's elevation ranges from 4085 feet to 5635 feet above sea level. The region encompasses over 2000 arches, spires, pinnacles, and sandstone monoliths and has layers of Navajo and Entrada Sandstone that reveal the effects of millions of years of deposition and erosion.

Cryptobiotic Soil
Long before the time of dinosaurs, the little organisms that comprise cryptobiotic soil were helping to create the earth's oxygen by "fixing" nitrogen for plant consumption. Appearing as a bumpy black crust, the soil prevents wind and water erosion and keeps the underlying dirt nutrient rich. It takes hundreds of years to form this special ground cover and only one footprint to destroy it. Because of the delicate nature of this special soil, its necessary to take precaution in order to preserve it. Stay on marked trails.

Monoliths
In geological terms, a monolith is a single massive rock feature, such as a mountain. The monoliths in arches are mainly comprised of Entrada Sandstone.

Natural Arches
Arches are formed as water and wind chisel into a narrow ridge surrounded by cliffs and gradually erode away layer upon layer of rock around and beneath the stronger sandstone structure, eventually carving the formation out of the cliff wall. Over 950 natural sandstone arches exist in the park, 43 having toppled since 1970. Arches can be seen in varying phases in Devil's Garden.

Hikes and Attractions

Landscape Arch
Considered one of the longest spans in the world, Landscape Arch is 191 feet long and 105 feet high. While it may have taken over 100,000 years to form, at only 6 feet wide, the arch is seemingly nearing its end. Spanning the distance of a football field, Landscape Arch rivals Kolob Arch in Zion National Park for the title of Worlds Largest Natural Arch

  • Part of the Devil's Garden, Landscape Arch is an easy 2 mile hike.
  • Alow 30-60 minutes for a round trip and include a a short side trip to Tunnel Arch.
  • The trail has a predominantly flat grave surface.

The Dark Angel
Near the beginning of the Primitive Loop Trail and 2.02 miles from the Devil's Garden Parkiing area sits the Dark Angel Monolith, named for the dark colored sandstone, the monolith is 150 high and sits on a bench overlooking the Salt Valley.

  • Begin at the Devil's Garden Parking Lot and Hike 2.02 miles to The Dark Angel.
  • Back track to the parking lot or finish the 7.2 mile round trip.
  • The trail is considered moderate, but parts are difficult during wet or snowy weather.

Learn More

Taking a ranger guided tour is a great way to learn more about the geology of the Park. Call the Visitors Information Center for more information or to reserve a guided tour with a park ranger.

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