Most rock at Capitol Reef is sedimentary, formed in layers from loose materials, like mud and sand. Geologists classify the rock layers into various formations. Many formations also have different parts, or members. These layers record the landscapes and lifeforms of a younger planet Earth.
Thin beds of reddish-brown shale were formed from silt and clay that came to rest in the quiet waters of lagoons, mud flats, and coastal flood plains. This 225 million year old rock is the Moenkopi Formation. The Moenkopi, more than 950 feet (290 m) thick in places, was laid down in a moist, tropical climate.
The banded gray and burgundy layers above the Moenkopi contain volcanic ash. The Chinle Formation, a complex, 700 foot (213 m) thick formation rich in petrified wood ascends to the base of a sheer cliff wall.