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Grand Canyon National Park

One of the scenic and geologic wonders of the world is the Grand Canyon in northern Arizona. The Grand Canyon is a huge gorge cut by the Colorado River over a period of millions of years. And the work of the Colorado River is far from complete. Each day the river and the forces of weathering combine in a process that continually widens and deepens the Grand Canyon.

Because of its scenic and scientific value, the area was designated a national park in 1919. In 1975 the Grand Canyon National Park was enlarged. It now includes areas formerly designated as the Grand Canyon and Marble Canyon national monuments.

The Grand Canyon is nearly 280 miles (450 kilometers) long and more than 1 mile (almost 2 kilometers) deep. It varies in width from more than 1 mile to 18 miles (about 2 to 29 kilometers). The land that rises from the canyon's floor is higher than any peak in the Appalachians. García López de Cárdenas became the first European to see the Grand Canyon in 1540. John Wesley Powell (1834–1902) conducted the first boat trip down the rapids of the Colorado River and through the gorge in 1869.

Each rock layer of the Grand Canyon holds a record of geologic history millions of years old. As the Colorado River cut deeply, forming the gorge, rock surfaces were exposed. Embedded in these surfaces are fossils. The fossils and the exposed rock layers give information on how the earth and life on it evolved. The canyon also has several different climates, stacked one on top of the other. Near the top, where it is coolest, there are blue spruce and aspen trees. Lower down, there are yellow pines.

Reviewed by George W. Carey Rutgers, The State University of New Jersey

"Grand Canyon National Park." Reviewed by George W. Carey. The New Book of Knowledge. Grolier Online, 2015. Web. 20 Sept. 2015.