Many of the people tell only about the canyon's story and not more about its numerous hues, strata, spires, and gorges. The place is so widely spread that neither the eye nor the mind of a beholder can think about not more than only a small part or it. John Wesley Powell for the first time traversed the canyon by river , in 1869 and wrote, "You cannot see the Grand Canyon in one view, as if it were a changeless spectacle from which a curtain might be lifted."

A mile below the edge, at the canyon's bottom, the Colorado River slices through Granite Gorge that exposes some of the oldest rocks visible anywhere on the earth. Nearly two billion years old, the Vishnu schist is the lustrous black relic of a once towering mountain range. After 500 million years it formed, vast rifting and faulting laid it down the tilted, colorful sediments of the Grand Canyon Series atop schist. Ten distinct layers of sandstone, limestone, and shale bespeak the advance and retreat of ancient seas, the building up and wearing down of mountains, the meandering of rivers over 600 million years. 

In Grand Canyon erosion has set a vigorous speed as compared with the nearly two-billion-year process of deposition. It is less than six million years old. It was created only since the Colorado River changed its track and began to flow through the ancestral Colorado plateau. In just two million years, the river sliced to within 500 feet above its current depth. The responsible factors for this change are- wind, rain, snow, heat, and cold. 

The Grand Canyon is not only slices the North America's geologic history but also makes a cross section of ecozones. The travelers find the same variety of ecological regions between the edge and the river on their trip from Canada to Mexico - from the snowy evergreen woods of the boreal zone to the scorched depths of the lower Sonoran, where summer temperatures soar above 100oF and tenacious shrubs like creosote and ocotillo predominate. It can be said in overall that the Grand Canyon provides rich and diverse habitat for more than 400 vertebrate species and 1,500 plants. 

The human presence here stretches back at least 4,000 years, beginning with hunter-gatherers who deposited delicate split-willow animal figures in limestone caves. Before disappearing about A.D. 1150, ancient Pueblo peoples who had lived in and around the canyon for a millenium or more left a rich legacy of pottery, baskets, pictographs, and granaries and other structures in thousands of sites. The Havasupai people in the region today trace their presence back hundreds of years. 

During the 20th century, humans have had a far more profound impact on the Grand Canyon than in all of the past. By 1900, the canyon was already a well-known destination, thanks to written accounts by explorers and scientists and to the glowing canvases of Thomas Moran. And after Grand Canyon National Park was established in 1919, the number of visitors continued to increase exponentially: About five million people now visit the canyon each year by car, on foot, atop mules, on motorized rafts, and in helicopters. Some of the human impact, such as the view-marring haze drifting in from power plants and urban centers, has been indirect. In 1963, the Glen Canyon Dam ended the Colorado River's free flow at the Grand Canyon's entrance, and that single action has changed the canyon more than any other event in human times. 

To John Wesley Powell a century earlier, the sound of rushing water in the canyon was "a symphony of multitudinous melodies." But with the flick of a switch, the ebb and flood that had shaped the canyon's complex ecosystems over countless millenia were halted. Since 1963, the ecological richness of the canyon has sharply declined. In 1996, officials opened Glen Canyon Dam for a weeklong test flood designed to imitate natural flooding. While it failed to right the ecological imbalances that had taken hold, the event marked an important acknowledgement that nature's imperatives, though easily tampered with, have their own logic.