Dark angel arches
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An additional sequence of stream-laid and windblown sediments, the Entrada Sandstone (about 140 Mya), was deposited on top of the Navajo. During the Early Jurassic (about 200 Mya), desert conditions prevailed in the region and the vast Navajo Sandstone was deposited. Over millions of years, the salt bed was covered with debris eroded from the Uncompahgre Uplift to the northeast. This salt bed is thousands of feet thick in places, and was deposited in the Paradox Basin of the Colorado Plateau some 300 million years ago (Mya) when a sea flowed into the region and eventually evaporated. The national park lies above an underground evaporite layer or salt bed, which is the main cause of the formation of the arches, spires, balanced rocks, sandstone fins, and eroded monoliths in the area. The park received more than 1.6 million visitors in 2018. The park receives an average of less than 10 inches (250 mm) of rain annually.Īdministered by the National Park Service, the area was originally named a national monument on April 12, 1929, and was redesignated as a national park on November 12, 1971. The highest elevation in the park is 5,653 feet (1,723 m) at Elephant Butte, and the lowest elevation is 4,085 feet (1,245 m) at the visitor center. The park consists of 310.31 square kilometres (76,680 acres 119.81 sq mi 31,031 ha) of high desert located on the Colorado Plateau. The park contains the highest density of natural arches in the world. More than 2,000 natural sandstone arches are located in the park, including the well-known Delicate Arch, as well as a variety of unique geological resources and formations. The park is adjacent to the Colorado River, 4 miles (6 km) north of Moab, Utah.