In America, there is so much magnificent scenery. Perhaps the most
stunning of all is the Grand Canyon in northern Arizona. It is the deepest,
widest canyon on Earth. This canyon is 217 miles long, 4 to 18 miles wide,
and in some places, more than a mile deep. The rocks at the bottom of the
steep walls are at least 500 million years old. Most of the rocks are
sandstone, limestone, and shale. By studying these rocks, scientists know
that this part of the world was once under the sea.