The
Grand Canyon, cut out by the Colorado River over a period of 15 million years
in the northwest comer of Arizona, is the largest land gorge in the world. It
is 4 to 13 miles (6.4 to 21 kilometers) wide at its brim, 4,000 to 5,500 feet
(1,219 to 1,676 meters) deep, and 217 miles (349 kilometers) long, extending
from the mouth of the Little Colorado River to Grand Wash Cliffs (and 277
miles, 600 feet or 445.88 kilometers if Marble Canyon is included).
However,
it is not the deepest canyon in the United States; that distinction belongs to
Kings Canyon, which runs through the Sierra and Sequoia
National Forests near East Fresno, California, with its deepest point being
8,200 feet (2,500 meters). Hell's Canyon of the Snake River between Idaho and
Oregon is the deepest United States canyon in low-relief territory. Also called
the Grand Canyon of the Snake, it plunges 7,900 feet (2,408 meters) down from
Devil Mountain to the Snake River. (The Handy Science Answer Book, compiled by
the Science and Technology department of the Carnegie Library of Pittsburgh)
