# Travel >> Destinations >> Central America

What the Grand Canyon's Walls Reveal: 2 Billion Years of Earth History

The exposed rock walls of the Grand Canyon are one of Earth's most complete and readable geological cross-sections, revealing nearly 2 billion years (2 Ga) of planetary history.

The Stratigraphic Column (Bottom to Top = Oldest to Youngest)

Era / Group	Age (Ma)	Key Formations	Environment / Story
Precambrian Basement	1,840–1,680	Vishnu Schist, Zoroaster Granite	Metamorphic roots of ancient mountains (Mazatzal/Yavapai orogenies). Deep crust exposed.
Grand Canyon Supergroup	1,250–730	Unkar & Chuar Groups	Rift basins, stromatolites (early life), glacial deposits (Snowball Earth?). Tilted, faulted.
Great Unconformity	~1,000–500	—	Massive erosion gap — 250–1,200 Myr missing. Planation surface.
Paleozoic "Layer Cake"	525–270	Tapeats Ss, Bright Angel Sh, Muav Ls, Redwall Ls, Supai Gp, Hermit Sh, Coconino Ss, Toroweap Fm, Kaibab Ls	Advancing/retreating seas: beach → shelf → deep marine → coastal plain → desert dunes (Coconino) → shallow sea (Kaibab). Rich fossils: trilobites, brachiopods, nautiloids, trackways.
Mesozoic (mostly eroded)	250–66	Remnants: Moenkopi, Chinle	Triassic river/floodplain (petrified wood, early dinos). Most stripped away.
Cenozoic	66–0	Basalt flows, gravels	Volcanism (Uinkaret field), Colorado River incision begins ~5–6 Ma.

What the Layers Tell Us

Deep Time & Crustal Evolution: Vishnu basement = assembly of North America's core.
Ancient Life & Oxygenation: Stromatolites (1.2 Ga) → Cambrian explosion (Tapeats) → vertebrate tracks (Coconino).
Sea Level & Climate Cycles: Transgressive/regressive sequences (Saucek, Tippecanoe, Kaskaskia, Absaroka cycles).
Desert vs. Sea: Coconino Sandstone (aeolian dunes, reptile tracks) vs. Redwall/Kaibab Limestone (tropical reefs).
Tectonics: Laramide uplift (70–40 Ma) raised Colorado Plateau → gave river gradient to carve canyon.
Canyon Carving: Colorado River incision accelerated ~5–6 Ma (Gulf of California opening). Knickpoint migration, terrace formation.