The Great Denudation is the uniformitarian name for the massive erosional event that stripped tremendous volumes of sedimentary rock from the surface of the Colorado Plateau. Like the origin of Grand Canyon, this event remains inexplicable to uniformitarian geology. However, any hypothesis of the origin of the Canyon must account for the conjunction of these two very large-scale, yet very different events. The Great Denudation was accomplished by east to northeast flowing sheets of water, which left a cobble and boulder lag—the Rim Gravel—on the southwest Colorado Plateau. Uniformitarians propose erosion by northeast flowing streams, but there is no sedimentary evidence for their depositional activity, and the sheet-like erosion is not consistent with observed styles of fluvial erosion. However, the Great Denudation can be easily explained by the sheet-flow phase of the Flood, which occurred early in the retreating stage. Evidence for a single, great, and rapid erosional event is found in the nature of the rocks capping the top two stairs of the Grand Staircase.