The Red Rock and the Deep Time Beneath Your Wheels

Every road in southern Utah runs across the floor of a vanished world. The red sandstone under the wheels is Jurassic desert, dunes of an ancient Sahara, lithified by time into Navajo Sandstone, the rock that makes Zion's cliffs and Arches' fins and Canyonlands' mesas. The rust comes from iron oxide, the same mineral that makes Mars red. In places the cross-bedding of the ancient dunes is still visible in the rock face, frozen in mid-curve, recording a wind that blew two hundred million years ago.

Go deeper and you find older stories. The Colorado River and its tributaries have cut through layers laid down from the Permian period through the Triassic, through the Jurassic into the Cretaceous, a nearly complete record of two hundred fifty million years of Earth history exposed in canyon walls you can read like pages. Dinosaurs walked this ground. The Morrison Formation, which runs across eastern Utah into Colorado and Wyoming, is one of the world's richest dinosaur-bearing rock units; the state fossil, the Allosaurus, is common here. Track sites from the Jurassic have been found in the San Rafael Swell, some of the largest known dinosaur footprints on the continent.

The human relationship with this geology is recent but intense. The first Euro-American to fully grasp its scale was John Wesley Powell, the one-armed Civil War veteran who ran the Colorado River through the Grand Canyon in eighteen sixty-nine, the same year the golden spike was driven at Promontory, five hundred miles to the north. Powell spent years mapping the canyon country and came away convinced that the entire region was too dry for large-scale agriculture without engineering on a scale that had never been attempted.

He was right. He was largely ignored. The settlement of Utah and the broader American West proceeded on assumptions of water abundance that the land itself did not support. The red rock canyon country absorbed the consequences: dams, reservoirs, diversions, and an ongoing argument about how much of the original world should be preserved. Utah has five national parks and more wilderness-quality land than any other state except Alaska. The argument is not over.