The most powerful force in the creation of the Grand Canyon has been erosion caused mostly by water, but also by the wind. Other contributors are the Colorado River, continental drift, vulcanism and the Earth’s orbit changing the climate.
Since the Grand Canyon is in a desert, water has the biggest impact. As the sun bakes the the soil, it cracks and becomes extremely hard. The tiny plants in the canyon have very shallow root systems due to the toughness of the ground and do nothing to deter the erosion.
Rainwater can wash down the surface of the canyon, taking with it rocks as big as cars. All of this debris runs into the Colorado River, which promptly whisks it away. As it goes, the debris tears more rock from the river bed and widens the gorge.
In the winter, the canyon snowfall melts and creeps into cracks where it refreezes. As it expands, the ice chips away even more rock. When the Rocky Mountain snows melt, the water sweeps down the canyon to carry away the debris.
Although the Glen Canyon Dam has slowed the erosion of the river, by slowing the spring floods, the canyon has another erosion slower. Where the top of the Grand Canyon is composed of softer rock, the base is composed of schist and granite. These volcanic rocks are much harder and take longer to erode.
As the North American plate moves onto the Pacific plate, the molten rock feeds the volcanoes of the Pacific Rim. All of this turmoil makes the continental plate buckle. This buckling is the cause of the western American mountains, as we know them today.
The sedimentary layers at the top of the canyon pay tribute to the change in climate. These sediments cover the roots of ancient mountains. The layers were deposited as the ocean rose and receded due to the rise and fall of sea level, which changes based on the melting and freezing of the polar caps.
Each layer of the Grand Canyon holds its own story in the history of the great gorge, each one a sign of ocean or river or snow or silt. The beauty of the Grand Canyon is as breath-taking, as its 20 million year striated story.
References: kaibab.org; holoscience.com; hypertextbook.com