The marvelous downcanyon view from the travertine outcrop at mile 1.55; so much geology to peruse, the layers of Paleozoic sedimentary rock and patterns of differential erosion resulting in multicolored cliffs and slopes, the bench-like Tonto Platform, the Great Unconformity, the crystalline basement rocks of Upper Granite Gorge, and blue-green ribbon of the Colorado River occasionally disturbed by patches of gregarious rapids.