Hance Rapid, named after famous Grand Canyon tour guide and storyteller John Hance, is located where Red Canyon intersects with the Grand Canyon at Colorado River Mile 77. Hance Rapid is a powerful whitewater rapid formed by debris from flash floods that tore through Red Canyon. This side canyon is composed of red Hakatai Shale, with dark shafts of volcanic rock called diabase cutting through it.
Dramatic Hance Rapid is formed by differential erosion between hard volcanic diabase, seen as a dark shaft in this photo, and the soft red shale that surrounds it.
Photo: NAU Cline Library, Bill Belknap Collection, NAU.PH.96.4.95.88
Whereas normally the Colorado River would eventually wear down the large boulders deposited at the mouth of the canyon, the volcanic rock is much harder than the soft shale. Therefore the diabase boulders eroded very slowly, and as the river plunged over them it hit the shale with greater force and eroded it even faster than normal. This differential erosion rate helped make Hance Rapid the biggest river drop along the Colorado River in the Grand Canyon; during normal water levels it falls 30 feet. It can be seen from Lipan Point on the South Rim, which is accessible from Desert View Drive, to the east of Grand Canyon Village.
Written By Sarah Bohl Gerke
References:
- Brian, Nancy. River to Rim: A Guide to Place Names Along the Colorado River in Grand Canyon from Lake Powell to Lake Mead. Flagstaff: Earthquest Press, 1992.
- Ghiglieri, Michael P. Canyon. Tucson: University of Arizona Press, 1992.