Published: March 2007



Rock of Ages

In canyon country, the depths of time are laid bare

By Mike Edwards
Photograph by Frans Lanting

In the outback regions of the Colorado Plateau, time stands nearly still. Year by year, erosion lightly planes the mesas and deepens the canyons; a wet year thickens the sparse grasses and a dry year withers them. But the sea of painted rock covering vast stretches of Utah, Arizona, New Mexico, and Colorado remains much as it was before the pioneers, before the Spanish conquistadores, before the first immigrants to the New World.

Shift your timescale from the human to the geologic, though, and the story of these corrugated rockscapes isn't scant change but vast change, hundreds of millions of years of it. Geologists often speak of deep time, the great spans over which the subtlest forces can remake a landscape. The canyonlands are a textbook of deep time.

During epoch after epoch, the Colorado Plateau grew like a Dagwood sandwich, built with layers of sandstone, limestone, mudstone, and shale. These strata—the time—pressed cargoes of oceans, rivers, and winds—were hoisted, sunk, and twisted by violent tectonic forces. Volcanoes spread lava on them, wind and water attacked them, and one of the world's most readable geology lessons took shape.

Geologists began more than a century ago to trace the score of strata that parade across canyons and mesas and to give them names: Wingate, Summerville, and—among the thickest and most extensive—Navajo sandstone. Some 180 million years old, the Navajo was built layer by layer over 15 million years by wind-deposited sand. It is more than 2,000 feet (600 meters) thick in places, tinged anything from subtle pink to lurid orange by iron oxides and cut by countless canyons.

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