A tar pit, or more properly asphalt pit, is a geological occurrence where subterranean bitumen leaks to the surface, creating a large puddle, pit, or lake of asphalt.
Animals are sometimes unable to escape from the asphalt if they fall in and this makes these pits excellent locations to excavate bones of prehistoric animals. La Brea Tar Pits have a museum built around the fossilized remains of mammals and birds found in such a tar pit.