asphalt: One of the heaviest petroleum fractions. Asphalt is what remains after all other fractions have been boiled off.

biodegradation: The natural process of bacteria and microorganisms consuming and helping to destroy an oil spill.

bitumen: A fraction of petroleum that is found in tar sands. To be usable, bitumen must be refined.

booms: A fencelike structure that lies on the surface of the water and helps to keep oil from spreading.

burning: The process of igniting and burning an oil spill. Burning is always done under controlled conditions, and, to work well, the spill must be fresh.

cracking: The process of refining a petroleum fraction into further chemicals and compounds.

crude: The term for petroleum in its natural state. Crude oil refers to petroleum that has not been refined.

dispersants: Chemical compounds that, when applied to an oil spill, will cause it to break down into smaller...