A water-carved Grand Canyon would have required millions of years of slow, steady erosion.
Moreover, Newberry and his successors judged the rock layers through which the Colorado River cut to be much older than the river, orders of magnitude older than the canyon itself.
6d - Kaibab Limestone 6c - Toroweap Formation 6b - Coconino Sandstone 6a - Hermit Shale 5 - Supai Group 4c - Surprise Canyon Formation 4b - Redwall Limestone 4a - Temple Butte Limestone 3c - Muav Limestone 3b - Bright Angel Shale 3a - Tapeats Sandstone 2 - Grand Canyon Supergroup 1b - Zoroaster Granite 1a - Vishnu Schist Over the centuries, the Grand Canyon has been many things to many people, such as a shelter for Native American groups, an obstacle to Spanish explorers, and an opportunity for Euro-American miners.
However, the Grand Canyon has been an especially important place for the study of geology.
Scientific observations made at the Grand Canyon helped them overturn older, typically European, ideas about time and geological change.