On river left, Redwall Cavern gapes at mile 33. The Colorado River carved this large cave from the Redwall limestone formation at river level. Explorer John Wesley Powell, clearly impressed at its vast size, wrote that it could hold 50,000 people (unlikely, but it is big!). River runners often stop here for lunch on the beach or a game of Frisbee inside the cavern’s sandy expanse, but no camping is allowed.

Grayish Muav limestone, the oldest of the Paleozoic rocks (formed about 500 million years ago), begins to appear at mile 34. The river continues to meander gently until mile 41, when it bends sharply east around Point Hansbrough, toward President Harding Rapid, before turning west toward Saddle Canyon.

This hairpin is an entrenched meander, a river bend deepened by downcutting. Above is Eminence Break, a northwest-facing escarpment formed along a fault line. A challenging route leads to the rim from the camp below President Harding Rapid.

On his second attempt at running the canyon, six months after hiking out of South Canyon, Robert Brewster Stanton discovered the body of Peter Hansbrough near this rapid. He buried Hansbrough here, leaving an inscription on the cliff as epitaph. The rapid was named by a later expedition, a USGS mapping survey led by Claude Birdseye, with Emery Kolb as chief boatman. The 1923 expedition carried a radio, and when they heard that President Harding had died, they camped here for a day and named the rapid in remembrance.

At mile 50, Bright Angel Shale appears, a late-Palezoic series of mudstone, sandstone, and limestone in shades of green, tan, and lavender. Easily eroded, it forms fantastic shapes farther downriver. In the central canyon, it is found on top of the Tonto Platform, where it has mostly eroded away from the underlying Tapeats sandstone, creating the rim of the inner canyon.