The Grand Canyon is a steep-sided gorge carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, one of the first national parks in the United States.

Geology
The geology of the Grand Canyon area exposes one of the most complete sequences of rock anywhere, representing a period of nearly 2 billion years of the Earth’s History in the part of North America. The major sedimentary rock layers exposed in the Grand Canyon and the Grand Canyon National Park area range in age from 200 million to nearly 2 billion years old. Most were deposited in warm, shallow seas and near ancient, long-gone sea shores. Both marine and terrestrial sediments are represented, including fossilized sand dunes from an extinct desert.

Geological Past
The Grand Canyon’s greatest significance lies in the geologic record that is so beautifully preserved and exposed in its walls. What is unique about the canyon’s geology is the great variety of rocks present, the clarity with which they are exposed, and the complex geologic story they tell. There are really two separate geologic stories at Grand Canyon. The older story is the one revealed in the thick sequence of rocks exposed in the walls of the canyon. These rocks provide an amazing, but incomplete record of the Paleozoic Era of 550-250 million years ago, and scattered remnants of Precambrian rocks as old as 2 billion years.

Geography
The Grand Canyon is a massive rift in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata, and is also one of the six distinct physiographic sections of the Colorado Plateau province. The Grand Canyon is unmatched throughout the world for the vistas it offers to visitors on the rim. Grand Canyon is known for its overwhelming size and its intricate and colorful landscape. Geologically it is significant because of the thick sequence of ancient rocks that are beautifully preserved and exposed in the walls of the canyon.

Rock Layers

1. The Inner Gorge has dark black schist and gneiss, and light pink granites. Schist and gneiss are metamorphic rocks, formed under intense heat and pressure, and literally changed from their original makeup.
2. Lying above the inner gorge are flat-lying or tilted layers of sedimentary rocks, sandstones, shales, limestones and conglomerates formed in environments like those we see on the surface of the earth today: rivers, floodplains, deserts, oceans, and beaches.
3. Superposition states that the oldest rocks in a stack of rocks are at the bottom, the youngest at the top.
4. Lateral Continuity states that layers will extend in all directions laterally until something causes that layer to disappear.
5. Original Horizontality states that sedimentary layers are laid down horizontal, or flat, and that if they are not flat, that must have happened after the layers were laid down.

This is all about the geology of Grand Canyon Area.

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