Carry a lawn chair and a sunshade—plenty of water too—onto the sage flats just south of Arizona's Highway 89A, near the mouth of Badger Canyon. Point the chair north, toward Utah, and take a seat. Behind you, the Colorado River is trenching a deep meander from the Glen Canyon Dam toward the Grand Canyon. Directly in front of you rises a chaos of rock vaulting nearly 3,000 feet—the Vermilion Cliffs. The cliffs can hardly be said to have a face. They have innumerable faces, fractured and serrated, crosshatched and slumped. You can feel the inertia in their colossal vertical fissures. Along the lower wedding cake tiers, rubble piles resemble the sand in the bottom of an hourglass.
And now the question: How long would you have to wait until the Vermilion Cliffs calved a boulder the size of a school bus, say? The answer: It could happen the day you sit down. But it's likelier that your descendants' descendants would still be sitting in that chair, many hundreds of generations later, waiting for the cliffs to crumble a little more. The rock is ancient, and so are the traces of erosion.
Millions of years ago, the spot where you're sitting would have been buried under the exposed layering of the present-day cliffs, under strata now called Moenkopi, Chinle, Moenave, Kayenta, and Navajo, each striation differing in color and resistance to erosion. The Paria Plateau has been retreating northwestward for eons, and these vivid cliffs mark its progress to date.