Among the wildland features specified in the Wilderness Act as worthy of protection are geological formations. Wilderness areas protect a vast array of landforms, displaying rocks forged across billions of years of Earth's history.
There are the ancient Precambrian exposures of the Boundary Waters Canoe Area Wilderness on the Canadian Shield and the Shenandoah Wilderness in the heights of the Blue Ridge. Contrast such staggeringly old rock with the comparatively youthful limestone islets of the Florida Keys Wilderness, many derived from coral reefs 150,000 years old or less. Or consider the relative transience of a sandy Mid-Atlantic barrier island, relentlessly sculpted by wind and waves, in New York's Otis Pike Fire Island High Dune Wilderness.
There's the soaring limestone vertebrate of the Chinese Wall in Montana's Bob Marshall Wilderness—an ancient, uplifted reef that is one of the great landmarks of the Northern Rockies. In the wildernesses of the Cascade Range—Glacier Peak, Goat Rocks, Mount Hood, Three Sisters, and other alpine paradises—travelers marvel at the interplay between fiery volcanism and gnawing glaciers. Worlds away from these mountain fastnesses are the floodplain landscapes of South Carolina's Congaree National Park Wilderness, where the alluvial processes of big coastal-plain rivers are fully on display.
The diverse coastal landforms of the Phillip Burton Wilderness on the Point Reyes Peninsula include everything from sea-sculpted headlands to the strike of the San Andreas Fault. In Utah's red-rock country, rivers have sliced steep-sided gulches through multicolored sedimentary monoclines in the Box-Death Hollow Wilderness. Southern Alaska's Glacier Bay Wilderness protects some of the world's grandest tidewater glaciers spilling down from towering oceanfront mountains. Ancient seafloor sediments and deposits washed out of the newborn Rockies form the pliable (and fossil-rich) layers that have been eroded into exotic pillars, castellated tablelands, and knife-edge ridges in the Badlands Wilderness of South Dakota.
An astonishing diversity of geological forces and a dizzying span of earth-time are on display in America's wildernesses, which safeguard pristine strata and invite musings on the planet's deep history.