With a span of 275 feet (84 meters), Rainbow Bridge arches to a height of 290 feet (88 meters). The top is 42 feet (13 meters) thick and 33 feet (10 meters) wide. The dark, vertical streaks on the sandstone, called "desert varnish," are composed of iron oxide or manganese. Many believe these particles leach from the rocks; others believe that minerals are blown as dust particles and settle on wetter areas of rock. Afternoon sunlight makes the colors especially brilliant.

The base of Rainbow Bridge is composed of Kayenta Sandstone, reddish-brown sands and muds laid down and consolidated hundreds of millions of years ago. Above its base the bridge is composed of Navajo Sandstone. This formation was created as wave upon wave of sand dunes were deposited to depths of 1,000 feet (305 meters). Over the next 1 00 million years, both these formations were buried more than 5,000 feet (1,524 meters) deep by other strata. The pressures and temperatures of this burial consolidated and hardened the rock of these formations.

Some 60 million years ago the landscape we know as the Colorado Plateau began a gradual uplift. Today's landscape results from the erosion caused by streams cutting into these massive layers of rock now lifted far above sea level. As the landscape lifted and tilted, these streams acquired more force and began to downcut their meanders.

As Bridge Creek entrenched itself into the landscape, the scene was set for carving Rainbow Bridge. As the canyon cut through the Navajo Sandstone and then hit the hard Kayenta Formation rock, the cutting became more difficult. The stream widened its path and undercut the canyon walls. Finally it cut through the neck of a meander loop. The stream then altered its course, taking the more direct course through the break. Huge flakes of sandstone broke loose and fell, leaving a conchoidal or shell-like pattern like that found in the chipping of Native American arrowheads. Natural flaking, called exfoliation, contributes to the formation of alcoves and natural bridges throughout this region.

Visiting Rainbow Bridge

You can reach Rainbow Bridge via 2 foot trails: from Navajo Mountain Trading Post, 14 miles (26 kilometers), and from abandoned Rainbow Lodge, 13 miles (24 kilometers). Required permits and detailed information on routes, water sources, and supplies may be obtained from the Navajo Nation (see below).

Both hiking trails traverse Navajo Nation land. Please respect the land and the privacy of the people living there.

Remember that hogans are private property. Allow livestock to graze undisturbed. Leave gates as you find them. Use a backpacking stove. If you must build a fire, use previous fire sites and extinguish fires completely. Pack out all trash. Bury human wastes 8 inches (20 centimeters) below ground, and away from water sources.

There is no campground or picnic area. A vault toilet is available. The nearest town with food, lodging, and facilities is Page, Ariz., on U.S. 89.

The Trailheads

The trailheads are near Navajo Mountain. The Navajo Mountain Trading Post trailhead is unmarked; trail starts at the end of the road. The Rainbow Lodge Rainbow Bridge trailhead lies at the west end of the old Rainbow Lodge ruins. Both trails lie on the Navajo Indian Reservation and terminate at Rainbow Bridge National Monument. The trails are not maintained and they cross rough canyon country. They are not recommended for the beginning, casual, or careless hiker. In summer the trails are hot and dry; in winter elevations make them subject to severe cold and high winds. Portions of both trails are subject to flash floods. You can use the two trails round trip fashion. You can also make advance arrangements with a park concessioner for boat transportation back to Wahweap from Rainbow Bridge.

Trail bikes and motorized vehicles are illegal. Horse use on the Lodge-Bridge trail is not recommended. Hikers must obtain a permit before hiking these trails. Write: The Navajo Nation, Recreational Resources Department, Box 308, Window Rock, AZ 86515; call 602- 871-6647, or 602 871-4941.