Eitan Checks Out The Scene, #1

 Imperial Point

The nearly 40 major sedentary rock layers exposed in the GC range from 200 million to ca. 2 billion years old.  The rock and other deposits (compressed by gravity over millions of years) formed in warm, shallow seas and near ancient, long-gone seashores in western USA.

The serenity broken by a geo uplift 75 million years ago creating a plateau two miles above sea level. From 6 million years ago, the Gulf of California enabled a large river to cut its way northeast from the gulf, capturing the older drainage systems, to form the Colorado River, which in turn started to form the Grand Canyon.

Wetter climates brought upon by ice ages starting 2 million years ago increased excavation of the Grand Canyon, which was nearly as deep as it is today by 1.2 million years ago. Volcanic activity deposited lava over the area 1.8 million to 500,000 years ago. At least 13 lava dams blocked the Colorado River, forming lakes that were up to 2,000 feet deep. Earthquakes and human activities (Glen Canyon Dam, etc) have reduced the Colorado River's ability to excavate the canyon.
(Sources, park brochures and wiki)