North Window natural arch, Arches National Park located north of Moab in the state of Utah, USA. Bordered by the Colorado River in the southeast, it's known as the site of more than 2, 000 natural sandstone arches, such as the massive, red-hued Delicate Arch in the east. 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. 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 when a sea flowed into the region and eventually evaporated. |