The Colorado River: Five Million Years of Canyon Building
Near Moab, Utah
The Colorado River carved the canyon country around Moab over roughly five million years, and the record of what it cut through is visible in the cliff walls on every side of the valley. The rock layers exposed around Moab represent approximately three hundred million years of geological time, from ancient formations at the base, laid down when this region was a shallow inland sea and accumulating deep salt beds that now deform under pressure and push the landscape into unexpected folds, to the relatively younger sandstone formations near the top that were once vast fields of wind-blown desert dunes. The Entrada Sandstone, the red and orange rock that forms the arches and fins of Arches National Park, was a dune field roughly one hundred fifty million years ago.
The individual grains of sand in that formation moved through a Jurassic desert. The stone under your feet on the canyon rim is petrified wind. The Colorado River itself is comparatively young in this ancient landscape.
The canyon cutting that created the Grand Canyon downstream and the canyonlands upstream is generally dated to the last five or six million years, though the exact timing is still debated, recent in geological terms. The river found faults and weaknesses in the plateau rock and followed them downward, cutting thousands of feet into the stone while the land slowly rose around it. The result is what you can see from Dead Horse Point or the canyon overlooks around Moab: a landscape that took longer to build than any human civilization has existed, laid open by a river that is still at work today.
