Petroleum, often referred to as "black gold", is a viscous, dark brown, or greenish flammable liquid that occurs in the upper layers of certain areas of the earth's crust. Petroleum contains only crude oil, but in daily use it is also used in the form of other solid, liquid an ...

Petroleum (also known as crude oil or petroleum), often referred to as "black gold", is a thick, dark brown or greenish flammable liquid that occurs in the upper layers of certain areas of the earth's crust. Petroleum consists of a complex mixture of various hydrocarbons, mostly the alk ...