听力原文：M: It's good to see you back. How was your trip to Arizona? Did you see the Grand Canyon? W: Yes, it was fantastic. Now I know why this is together with a wild river as one of the great natural wonders of the world. Here, want to see the pictures I took? M: Oh, what a view! It's even bigger than I imagined. I remember reading about the Grand Canyon. I think it said that it was formed suddenly when the earth cross-split during an earthquake. W: Well, not that quickly. Look, here is a picture of the Colorado River. She wears down the body of the canyon. That river and its tributary have been wearing away the canyon floor for over 10 million years. M: Then the canyon is the result of soil erosion. I bet geologists have made some interesting discoveries there. W: Not only the geologists, archeologists have found the bones of ancient animals in caves and canyon walls. In a cave 140 feet above the river, they found driftwood that dates back as far as 37000 years. M: That means, the river must have been 140 feet higher to carry the wood into the cave. W: It's very possible. But of course who knows. The Grand Canyon is full of mysteries. Wouldn't you like to go to Arizona some day? M: You bet I would! Where has the woman been?