Oil is a product used by everyone, but sometimes oil is a problem. An oil spill is a leakage from an oceangoing tanker, pipelines, or other oil sources. Oil spills occur very frequently, and cause enormous ecological harm. About eight million barrels of oil are spilled each year. Tankers usually carry about five-hundred million barrels of oil. Many oil spills, large in land or ocean coverage, have had major impacts on the earth and it's inhabitants. Many animals are die and some are injured in some way. Many plants and animals are endangered, or are now extinct. The largest oil spill to occur was when the Exxon Valdez went aground and covered 4,800 square miles in Prince William Sound, Alaska. This spill killed 35,000 sea birds, 10,000 otters, and at least nine whales. The spill left pools of oil up to three feet on some beaches. In December of 1989, an Iranian tanker leaked 70,000 tons, about 19 million gallons of oil off of the coast of Morocco. In January 1990 a broken Exxon pipeline leaked 567,000 gallons into the New York harbor. In June of 1990, another 260,000 gallons were spilled in New York Harbor. A tanker carrying 38 million gallons of oil caught on fire, and leaked oil into the Gulf of Mexico. This was a very serious threat to local shrimp nurseries and wildlife refuges. In February of 1990, 300,000 gallons leaked from a damaged tanker off Southern California, fouling miles of shoreline. In the Niger River delta, in Nigeria, Shell pipelines have repeatedly burst. In 1970 oil spilled across 8 square km, which remained contaminated for over 20 years. According to the U.S. Coast guard, the incident rate post is only 0.5 spills per year. In fact, there have been no large spills over 5,000 barrels from tankers in the US since 1991. The US Coast Guard data shows that the amount of oil spilled by tankers has decreased dramatically. Worldwide pollution from tanker spills is a relatively minor source of marine pollution.