For rafters on the Colorado River, the geologic splendor of the Grand Canyon rises at times a mile above them. The canyon's inner gorge opens and closes, revealing and concealing sweeping vistas of towering cliffs, buttes and mesas. Floating downstream is a multihued descent through a North American geologic timeline.

The descent can also be sweltering. Arrival at the tapeats' ledges represents the chance to get out of the beating sun and enjoy some cool shade. This layer of the Canyon was formed nearly half a billion years ago when Cambrian Seas covered the American southwest. Its exposure by the relentless, erosive force of the Colorado is a godsend to the river-borne tourist. For rafters on the Colorado River, the geologic splendor of the Grand Canyon rises at times a mile above them. The canyon’s inner gorge opens and closes, revealing and concealing sweeping vistas of towering cliffs, buttes and mesas. Floating downstream is a multihued descent through a North American geologic timeline.