The Canyon’s Clues to Earth’s History

Kaibab Limestone

250 million years old

This creamy to grayish-white limestone was formed by a shallow sea advancing and retreating many times. This layer tops both rims. Fossils found here include sponges, corals, and brachiopods (small sea animals).

Toroweap Formation

260 million years old

This slope is pale yellow to gray crumbly limestone, sandstone, and shale. Reptile footprints show that this zone was a desert once, when it was the surface of this area.

Coconino Sandstone

280 million years old

These are mighty cliffs of sandstone, a layer deposited by wind, which blew sand across the region. Tracks of spiders, scorpions, and lizards are found here.

Hermit Formation

285 million years old

The red of this crumbly shale comes from iron oxide—rust! It holds fossils of reptiles and amphibian tracks along with insects, including a large dragonfly. The shale also contains many worm burrows. Plant fossils of conifers and ferns suggest that, very early, there was plenty of rainfall and maybe even forests.

Supai Group

300 million years old

Looking like red stairs, these shale, limestone, and sandstone layers formed when amphibians first evolved. Fossils include corals and other small sea animals. In some places, there are land plants and reptile tracks.

Redwall Limestone

340 million years old

This sheer limestone cliff forms a barrier that is difficult to cross. This layer divides the forest above it from the desert below. Stained red by iron oxides washed down from the layers above, the area is pitted with caves. Fossilized remains of sea animals are found here.

Temple Butte Limestone

350 million years old

In the western region, there are cliffs hundreds of feet high. The color of this layer ranges from purple in the east to gray or cream in the west, and many marine fossils are found here.

Tonto Group

Group of layers 530 million years old

Muav Limestone (top left)
A gray limestone separated by shale and sandstone, this layer has few fossils.

Bright Angel Shale (top center)
Created from mud left after water washed over the area, the shale is mostly a green color. The rock contains fossils of sea animals.

Tapeats Sandstone (top right)
Dark brown in color, this layer contains fossils of sea animals.

Vishnu Complex

1 to 2 billion years old

The hard rocks at the bottom of the canyon are the oldest ones. They were spit out as lava during volcanic eruptions. The melted rock cooled and hardened into a wide variety of colors—gray, black, blue, and even pink.