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Rock art is the name given to pictures drawn on rock by ancient people. In the American Southwest, rock art can be seen on the walls of caves and mountains. Many of these places are in the Four Comers area, where the states of Arizona, Colorado, Utah, and New Mexico meet. More than 7,000 rock art places have been found just in Utah, where the area’s dry climate （气候）has helped keep the art.

There are three forms of rock art. The first is petroglyphs, which are pictures carved （雕刻）into the surface of rock. A sharp （尖利的）stone may have been used as a carving tool. A heavy stone may have been used to hit the sharp stone into the surface. The second form of rock art is pictographs, which are pictures painted on the rock. The paint was made from plants and trees. The artists painted with fingers, brushes made from hair, or bird bones. The third kind of rock art is geoglyphs, which are designs made in the ground by taking away stones.

Some rock art shows faces, hands, animals, and trees. Other pictures are symbols such as lines, circles, and squares. Some scientists think these symbols marked the location of water or good hunting grounds. Some think the symbols were put there during special celebrations. Others think the symbols showed the movement of planets and stars. Still others believe that they are just doodles.

Some rock art may be a form of writing. Large scenes are shown on mountains. Some scenes seem to tell a story. A hunting scene may include animals and people with hunting tools. A scene with many people holding hands could mean friendship. Rock art in caves may have been a way to decorate the artist’s home.

Some rock art in the Southwest is about 200 years old. Other rock art may be 10,000 years old. Scientists think ancient people called the Anasazi created the older works. They were farmers and lived in caves.