Petroleum, also known as crude oil or simply oil, is a natural resource that appears yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term petroleum refers both to naturally occurring unprocessed crude oil, as well as to petroleum products that consist of refined crude oil.
Petroleum is a fossil fuel formed over millions of years from anaerobic decay of organic materials from buried prehistoric organisms, particularly planktons and algae.
