Since this comment got some attention, my source for this was [0] Ranney, Wayne. “How Rivers Carve Canyons.” Carving Grand Canyon - Evidence, Theories, and Mys

Since this comment got some attention, my source for this was [0] Ranney, Wayne. “How Rivers Carve Canyons.” Carving Grand Canyon - Evidence, Theories, and Mystery, 2nd ed., Grand Canyon Association, 2012.