One of many arches at the park, Arches National Park, 2015.

Arches National Park has the densest concentration of natural stone arches in the world! Over 2,000 arches are documented in the park, ranging from sliver-thin cracks to spans of 300 feet (97 meters). The park has just the right combination of fine-grained sandstone atop a denser layer of sand and clay which combine with buried layers of salt and a small amount of precipitation (about 8-10 inches per year). This cracks the ground and erodes at just the right rate to create these arches instead of eroding equally across the region.