Dark Sky Sanctuary
PO Box 1507
691 Scenic View Dr
Page, AZ 86040 USA
Rainbow Bridge National Monument is a 65-hectare (160 acre) site in the U.S. state of Utah that preserves one of the tallest and longest natural bridges in the world. The bridge was created by Bridge Creek during the last glacial period, during which it encountered layers of sandstone of different durability deposited in the area during an extended arid period during the Triassic and Jurassic geologic eras. The water diverted around what became the bridge after eroding away softer rocks from the harder sandstone beneath them. Continuous washing of the creek water, containing abrasive quartz grains, against each side of the turn eventually eroded a continuous passage through its center.
The bridge, of cultural importance to a number of area Native American tribes, has been designated a Traditional Cultural Property by the U.S. National Park Service. Evidence of human habitation in the area extends back at least a thousand years; the modern Pauite and Navajo people came to call the structure Nonnezoshe or “rainbow turned to stone.” Nearby inhabitants continue to revere the bridge as a sacred place. Due to its extremely remote location in difficult terrain, the existence of the bridge was not known to European-Americans until 1909.
Its remote setting has also kept Rainbow Bridge well away from later European settlement; to this day, it is only accessible via a two-hour boat ride on Lake Powell from marinas near Page, Arizona, followed by a mile-long hike, or by hiking overland for several days from a trailhead on the south side of Lake Powell. As a result, the site remains naturally dark; the U.S. National Park Service Natural Sounds and Night Skies Division estimates that artificial light at the zenith is less than five percent above the natural background level. Given the Monument’s protected status and isolated location, and taking into account its essentially pristine night skies, it is especially appropriate to the International Dark Sky Sanctuary label.