Rock of Ages
Look down from one or the many viewpoints along the park’s Rim Trail, and if you’re lucky, you’ll catch a glimpse of the Colorado River winding along the canyon floor. Standing there at 7,000 feet above sea level, it’s easy to marvel at how the thin ribbon of water a mile below helped carve the canyon into the awe-inspiring natural wonder at your feet.
But that tale’s only one of the many hidden within the walls of the Grand Canyon. Staring down into its chasm, you’re glimpsing nearly 2 billion years of the Earth’s geological history, and researchers have been studying it since shortly after the Civil War, when the explorer and geologist John Wesley Powell led the Powell Geographic Expedition down the Green and Colorado rivers through the Grand Canyon.
While the oldest rock formation in the park belongs to the Vishnu Basement Rocks, most visitors marvel at what are actually the youngest rocks in the park. Heavily eroded by wind, rain, cold, and heat, the 40 or so layers of sedimentary rock formed over many hundreds of millions of years when water covered much of the landmass now called North America. Marine life, tiny and monstrous, populated the Western Interior Seaway and silt, mud, and other sediments from ancient mountain ranges filtered down over aeons to fill its depths. Heat and pressure turned sediments into the strata seen from the Rim Trail; then crustal movement lifted 130,000 miles of the Colorado Plateau (and the Grand Canyon along with it) as much as 2 miles above its original elevation. Can you imagine the amount of energy required to lift bedrock and millions of tons of earth more than 10,000 feet in the air?
Among the other mysteries one can contemplate while gazing into the Grand Canyon: During the 2 billion years that the Grand Canyon emerged above the Vishnu Basement Rocks, as many as five supercontinents formed, plate tectonics forcing the ancient land masses together; then splitting them apart again. The most recent, Pangea, formed approximately 300 million years ago.
Mountain ranges along the hemisphere’s Ring of Fire—from Alaska to Antarctica—erupted from the depths, pushed up by volcanic activity and the collision of tectonic and lithosperheric plates. The proto-North American continent migrated from the Equator to its present position in the Northern Hemisphere.
Dinosaurs sprang into existence. And then disappeared, leaving fossils (some evident in the walls of the Canyon) behind. Birds, evolving from Theropods, first appeared during the Jurassic Era (between 145.5 and 4 million years ago) and their descendants (like the California Condor) now fly above the Canyon. Prehistoric megafauna, including the Wooly Mammoth, the 8-foot tall Bison latifrons, 6-foot long Glyptotherium, American Lion, and Camelops roamed North America, and descendants of a handful of those ancient species, such as the American Bison and Pronghorn, still survive.
Approximately 200,000 years ago, a new mammalian species emerged in Eastern, sub-equatorial Africa. Inquisitive and restless, many within the growing population began a great migration in search of new territory to forage and explore. That migration took them to northern Africa, the Mediterranean, the Iberian peninsula, eastern and western Europe, India, the far East, and up into the Steppes of Eurasia. Their still restless descendants, surviving an ice age on the subcontinent of Beringia, migrated, as many as 20,000 years ago, into North America after the last glaciers departed. After establishing settlements in Alaska and western Canada, they roamed further, spreading east across the remainder of Canada, eventully becoming known as the First Nations people. Continuing south, Ancient Puebloan people explored and migrated over most of the western United States. Their descendants eventually settled in the areas surrounding the Four-corners region of the American Southwest, including the Grand Canyon, where the Hopi, Havasupai, and Hualapai still reside.