When the Exxon Valdez grounded, a little after midnight, the third mate was driving the boat. Before collision the captain had changed the normal coarse to avoid hitting icebergs. The crude oil poured out of the tankers hold at forty-two thousand four hundred eighty-eight barrels an hour.

Oil spills can be caused by accidents with tankers, barges, pipelines, refineries, and storage factories. The oil will always float on salt water and usually floats on fresh water. If the oil is heavy enough it might sink to the bottom of the body of water. This rarely ever happened though. The oil will spread fast on the surface to form a thin layer over the water slick. The oil can spread out to an even thinner layer called a sheen.

The oil is very dangerous to marine animals, land animals, and humans. It usually affects marine birds, mammals, fish, and shell fish. The oil destroys the insulating ability of fur-bearing mammals. It also destroys the water repelling abilities of a birds feathers.