An oil spill is the common expression used to refer to the release of crude oil or petroleum into water or on land. Crude oil released in this way represents an evironmental issue of great concern because spills threaten animals, plant life and other marine resources. Oil can also cause long term environmental and economic damage to the marine ecosystem near a spill. According to a 2002 report from the National Academy of Sciences, approximately 210 million gal (790 million l) of oil spills into the oceans each year. Sources include the wells from which oil is extracted and the ships used to transport it, as well as natural oil seepage from geologic formations below the seafloor, as for example in Coal Oil Point along the California Coast, where an estimated 2,000–3,000 gal (7,570–11,350 l) of crude oil is released naturally from the ocean floor every day. While accidental tanker oil...