The active movement of the San Andreas and other faults allows oil and gas from subterranean reservoirs to seep up to the ocean floor. | Jack Cook, Woods Hole Oceanographic Institution

World's Oldest Oil Spills: Asphalt 'Volcanoes'

These undersea mounds of asphalt have been leaking oil for tens of thousands of years.

April 28, 2010
3:00 AM EDT