Flexi Says: Counting layers of rock in the Grand Canyon is not straightforward, because the answer will vary depending on the scale of layering that is being analyzed. The National Park Service lists 18 major rock formations in the Grand Canyon. Of those, 11 make up the most visible sandstone, shale, and limestone layers associated with the canyon. However, many of these individual rock formations are built up from smaller-scale layers of alternating ("interbedded") sandstone and shale that were deposited over millions of years.
