In parts of the world that have long, dry seasons, some rivers carve deep valleys called canyons. The rivers get their water from mountains far away, or from underground. When rain falls on canyons, it is usually in short, heavy bursts. There is little soil and. few plants to soak up the water, so it rushes over the land, carrying loose rocks with it. Two of the world's most spectacular canyons are the Grand Canyon in North America and the Nile Canyon in Egypt.