The canyon's layers

Top to bottom
 
 
 
KAIBAB FORMATION

AGE: 250 million years
(Permian Period, Paleozoic Era)

THICKNESS: 300 feet

COMPOSITION: Mostly limestone; some sandstone and shale.

NOTES: The Kaibab Formation combines with the two layers immediately below it to form the whitish cliffs at the top of the Grand Canyon. These sedimentary layers are the canyon's youngest, but they are still old enough to predate the dinosaurs.

 
 
 
 
TOROWEAP FORMATION

AGE: 255 million years
(Permian Period, Paleozoic Era)

THICKNESS: 250 feet

COMPOSITION: Limestone and sandstone

NOTES: The Toroweap Formation's gentler slope accommodates tree growth, creating a green band between the whitish cliffs of the Kaibab Formation above and the Coconino sandstone below.

 
 
 
 
COCONINO SANDSTONE

AGE: 260 million years
(Permian Period, Paleozoic Era)

THICKNESS: 325 feet

COMPOSITION: Quartz sandstone

NOTES: These huge white cliffs were formed by ancient sand dunes.

 
 
 
 
HERMIT SHALE

(Permian Period, Paleozoic Era)

AGE: 265 million years

THICKNESS: 300 feet

COMPOSITION: Shale

NOTES: Shale is formed by silt or clay deposits.

 
 
 
 
SUPAI GROUP

AGE: 285 million years
(Pennsylvanian Period, Paleozoic Era)

THICKNESS: 600 feet

COMPOSITION: Shale and sandstone

NOTES: The Supai actually is a combination of four separate formations. The top one, a sandstone layer, forms the Esplanade plateau in the western part of the Grand Canyon.

 
 
 
 
REDWALL LIMESTONE

AGE: 335 million years
(Mississippian Period, Paleozoic Era)

THICKNESS: 500 feet

COMPOSITION: Limestone and dolomite

NOTES: The cliffs of the Redwall are actually gray rock stained red by runoff from the Supai above.

 
 
 
 
TEMPLE BUTTE LIMESTONE

AGE: 350 million years
(Devonian Period, Paleozoic Era)

THICKNESS: 80 feet

COMPOSITION: Limestone

NOTES: This formation appears only intermittently in the eastern part of the canyon, but in the west it forms large and continuous cliffs.

 
 
 
 
MUAV LIMESTONE

AGE: 515 million years
(Cambrian Period, Paleozoic Era)

THICKNESS: 400 feet

COMPOSITION: Mostly limestone; some sandstone and shale.

NOTES: A gap of 150 million years exists between the times the Muav Limestone and the canyon's next-youngest layer, the Temple Butte Limestone, were formed.

 
 
 
 
BRIGHT ANGEL SHALE

AGE: 530 million years
(Cambrian Period, Paleozoic Era)

THICKNESS: 375 feet

COMPOSITION: Shale; some sandstone and limestone

NOTES: If you hike the canyon, you probably will walk many a mile on Bright Angel shale; it is the rock of the Tonto Plateau.

 
 
 
 
TAPEATS SANDSTONE

AGE: 545 million years
(Cambrian Period, Paleozoic Era)

THICKNESS: 100 feet

COMPOSITION: Sandstone

NOTES: This is the last layer before the rocks of the Precambrian Era -- when life was a whole lot simpler.

 
 
 
 
GRAND CANYON SUPERGROUP

AGE: 1.2 billion years
(Precambrian Era)

THICKNESS: Varies; several hundred feet

COMPOSITION: Primarily sandstone

NOTES: The distinctive tilted strata of the Grand Canyon Supergroup appear only intermittently in the western part of the canyon. The Supergroup is a prominent feature, however, from Red Canyon eastward; in that part of the canyon its thickness is like that of the Vishnu schist in the west.

 
 
 
 
VISHNU GROUP

AGE: 2 billion years
(Precambrian Era)

THICKNESS: 800 to 1,500 feet

COMPOSITION: Metamorphic gneiss and schist, laced with bands of pink Zoroaster granite.

NOTES: This rock is about half as old as Earth itself.

 
 

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