No matter how much you read about the Grand Canyon or how many photographs you've seen, nothing really prepares you for the sight of it. One of the world's seven natural wonders, it's so startlingly familiar and iconic you can't take your eyes off it. The canyon's immensity, the sheer intensity of light and shadow at sunrise or sunset, even its very age, scream for superlatives.
At about two billion years old – half of earth's total life span – the layer of Vishnu Schist at the bottom of the canyon is some of the oldest exposed rock on the planet. And the means by which it was exposed is, of course, the living, mighty Colorado River, which continues to carve its way 277 miles through the canyon as it has for the past six million years.