PETRIFIED FOREST Guidebook 1961

THE PAINTED DESERT

The part of the Painted Desert that is included in the monument exhibits practically all the usual forms of badlands erosion.

The badlands of the Painted Desert are of the same age (Triassic) as those of the Rainbow Forest to the south. They are composed of water-deposited layers of volcanic ash, interbedded with thin layers of shale, sandstone, and river gravel. The alteration of the ash has converted it into a claylike substance that is called bentonite.

Agate Bridge in 1899.

Hard and strong when dry, bentonite will, however, absorb water like a sponge and with enough moisture will disintegrate into a fine flowing mud. Thus it is that in this semiarid region, with its long dry season and its torrential summer rains, the bentonitic beds are rapidly cut into turreted ridges, conical hills, and small steep-walled canyons and ravines.

In places, a hard covering, or caprock, of sandstone or lava may serve to protect the soft layers beneath, resulting in the formation of abrupt-sided mesas and buttes.

The most amazing property of the Painted Desert is the everchanging quality of its colors. Pure bentonite is nearly white, but here minute quantities of iron oxide in the volcanic ash have stained the layers to many shades of red, blue, brown, and yellow. These colors are most vivid immediately after a rain in the early morning or late evening, and cloud shadows create a kaleidoscope of moving colors.

A 6-mile drive along the rim of the Painted Desert has a number of overlooks from which there are superb views. Rapid erosion of the desert soils makes it impossible to maintain either roads or trails into the desert below the rim. Consequently, the Black Forest, a concentration of dark petrified wood, is virtually inaccessible. While you are not prohibited from entering the desert, you should not attempt it unless you are conditioned to desert hiking, and you must give prior notice of your trip to a park ranger.