On the Nevada-Arizona border, 9 miles south of Hoover Dam, the Colorado River runs with the devil. It courses through Black Canyon, which, thanks to a series of fault zones, disgorges heat from the fire below. Hot waterfalls cascade from its walls; steam rises from its springs. And there are illusions here: When the sun drops low in the west, a dark cavern becomes a brilliant gem. Photographer Kerrick James casually dubbed it "Emerald cave" when he photographed a kayaker at play in the light, and the name has stuck with locals. "It's like a sea cave in Hawaii ― but it's in the desert," marvels James. To see Black Canyon for yourself, hook up with a river outfitter such as Black Canyon / Willow Beach River Adventures (www.blackcanyonadventures.com or 800/455-3490).
