阅读理解

　　Probably you have seen photographs of the Grand Canyon (大峡谷)，the great valley in the desert country of Arizona (亚利桑那州)．But you must go there yourself to feel its true size and beauty．The Grand Canyon is one of the greatest natural wonders of the world．

　　The Colorado River formed the Grand Canyon over millions of years．Slowly，the river cut down through hard rocks．At the same time，the land was rising．Today，the canyon is one and a half kilometers deep and 445 kilometers long．The oldest rocks at the bottom of the canyon are more than one billion years old．The width varies (变化) from about 200 meters to 29 kilometers across．The rim or top of the canyon is about 2 300 meters above sea level on the South Rim，and about 3 000 meters on the other side，the North Rim．As a result，there are different kinds of plants and animals on opposite sides of the canyon．The South Rim is a dry desert country．The North Rim has tall forest．

　　The canyon looks different at different times of day，and in different seasons and weather．At sunrise and sunset，the red，gold，brown and orange colors of the rocks are especially clear and bright．In winter，the canyon is partly covered with snow．

　　The view from the South Rim of the Grand Canyon is the best．Most visitors come to the South Rim and stay in campgrounds or hotels．Every point along the canyon's edge offers a different view．

　　The North Rim of the canyon is quieter．It takes all day to drive there from the South Rim because there is only one bridge across the Colorado River．On the way，you go through Navaho Indian land,and a colorful pink desert called“The Painted Desert”．

　　You can walk down into the Grand Canyon,or you can take a boat trip down the Colorado River， and camp on the beaches at night．But whether you see the Grand Canyon from the top or the bottom，or from the North Rim or South Rim，it will be an experience that you will never forget．

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