Oil spill refers to any unintentional release of an oil into the environment due to human activity (releases of crude oil from tankers, offshore platforms, drilling rigs and wells).
Oil spills have extremely negative environmental impact, they cause great damage to marine wildlife, and particularly vulnerable are birds because oil makes them extremely sensitive to temperature fluctuations and much less buoyant in the water, and once birds ingest oil that covers their feathers this causes serious kidney damage, altered liver function, and digestive tract irritation, leading to death in many cases.
Oil pollution is much more serious problem than many people think it is. In fact, in period between 1990-1999 an average of 150,000 tons of oil spilled each year into the world's waterways.
In order to determine the volume of some oil spill researchers observe the thickness of the film of oil and its appearance on the surface of the water. If the surface area of the spill is also known, the total volume of the oil can be easily calculated.
Probably the most famous oil spill of all time is Exxon Valdez oil spill that occurred in 1989. Exxon Valdez released around 11 million gallons of crude oil causing deaths to many marine animals, especially birds.
Oil spills are usually cleaned with dispersants that have the ability to break down oil much quicker compared to some other cleaning methods. However, these dispersants can be also quite harmful for environment because they can be absorbed by marine life, and some studies have even showed that in some cases these dispersants do much greater environmental damage than the spill itself.
Gulf of Mexico oil spill is the worst oil spill in the U.S. history, and its cleaning costs will climb over 1 billion dollars.