Grand CanyonA powerful and inspiring landscape, the Grand Canyon overwhelms our senses through its immense size; 277 river miles (446km) long, up to 18 miles (29km) wide, and a mile (1.6km) deep. The Grand Canyonis a steep-sided gorge carved by the Colorado River in the United States in the state of Arizona•The Channeled Scablandsare a unique geological erosion feature in Washington state. •They were created by the cataclysimic Missoula Floods that swept periodically across eastern Washington and down the Columbia River Plateau.Nearly two billion years of the Earth's geological history have been exposed as theColorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. While the specific geologic processes and timing that formed the Grand Canyon are the subject of debate by geologists,recent evidence suggests the Colorado River established its course through the canyon at least 17 million years ago. Since that time, the Colorado River continued to erode and form the canyon to the point we see it as today.
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