A scientific theory is an explanation for a naturally occurring event that has been developed by extensive observation, experimentation, and reasoning. Often a theory integrates the information accumulated by many different scientific disciplines. As new information is discovered theories may be modified, but they are rarely discarded. The theory of continental drift was proposed by Alfred Wegener, a German scientist, in 1915. He believed that the continents had once been joined together as one supercontinent, which he named Pangea. What evidence did Wegener use to support his theory?