Reading the Grand Canyon's Rock Layers: A Geologic Storybook

The Grand Canyon exposes nearly 2 billion years of Earth history in a single vertical mile. Each layer is a chapter—here’s the CliffsNotes version from rim to river.

Top-Down Layer Guide

1. Kaibab Formation (Permian, ~270 Ma)

Fossil-rich limestone—sponges, brachiopods, corals. Forms the rim’s caprock. Quarried for building stone.

2. Toroweap Formation

Thin, slope-forming sandstone and gypsum—evaporites from a retreating sea.

3. Coconino Sandstone (Permian, ~275 Ma)

Cross-bedded, wind-blown dunes (aeolian). White cliffs, fossil trackways of early reptiles. “The Sahara of its day.”

4. Hermit Shale (Permian, ~280 Ma)

Red mudstone/siltstone—floodplain deposits. Plant fossils (ferns, conifers), invertebrate tracks.

5. Supai Group (Pennsylvanian–Permian, ~315–285 Ma)

Red beds: sandstone, shale, limestone. Coastal plains, tidal flats, fluvial channels. Aquifer for springs.

6. Redwall Limestone (Mississippian, ~340 Ma)

Massive cliff-former, stained red by iron oxide from above. Caves, chert nodules, crinoid/brachiopod fossils. Major aquifer.

7. Temple Butte Formation (Devonian, ~385 Ma)

Discontinuous freshwater limestone lenses in eastern canyon; marine in west.

8. Muav Limestone (Cambrian, ~505 Ma)

Thin-bedded, shaly limestone. Trilobites, brachiopods. Forms slopes and ledges.

9. Bright Angel Shale (Cambrian, ~515 Ma)

Greenish-gray mudstone, siltstone. Trilobite-rich. Forms the broad Tonto Platform.

10. Tapeats Sandstone (Cambrian, ~525 Ma)

Basal cliff, coarse quartzite, conglomerate. Beach/deposits on Precambrian basement. Great Unconformity below.

Below: Vishnu Basement Rocks (1.7–1.8 Ga)

Metamorphic schist, gneiss, and granite—the ancient core of the continent.

Why It Matters

These layers record sea-level cycles, mountain building, desertification, and the explosion of early life. Hiking down is literally walking backward through deep time.