Down beneath the tourist lodges and shops selling keychains and incense, past windswept arroyos and brown valleys speckled with agave, juniper and sagebrush, the rocks of the Grand Canyon seem untethered from time. The oldest ones date back 1.8 billion years, not just eons before humans laid eyes on them, but eons before evolution endowed any organism on this planet with eyes.
Spend long enough in the canyon, and you might start feeling a little unmoored from time yourself...