Asphalt is found in places where there is or used to be petroleum. It may flow slowly out of the ground and collect in pools. The asphalt that comes from the ground is called natural asphalt. Asphalt can also be made from petroleum.
When asphalt stands, it changes from a thick liquid to a soft solid. Chunks of asphalt are often found floating on the Dead Sea. In early times much asphalt was mined near this sea. Farther north. in Mesopotamia, the land between the Tigris and Euphrates rivers, there were many asphalt springs, too. The people in that región long ago cemented bricks together with asphalt to make pavements. They also sealed jars with asphalt.
The famous tar pits of California are pools of asphalt. In these pools scientists have found many wonderful fossils of mammoths, sabertooths, vultures, and other animals of the great Ice Age. So many fossils have been found in these pools that sometimes they are called "the deathtrap tar pools."
It is not hard to see how the deathtraps worked. After a rain, water covered the asphalt. Animals that waded out to get a drink became caught in the sticky substance and began to sink. Meat eaters—wolves and sabertooths—saw them and sprang on them. Then the meat eaters were caught, too.
