Formation
Crude oil is formed from ancient biomass. When animals and plants (such as plankton) died over millions of years ago in the oceans, they fell to the bottom of the ocean and decayed anaerobically in mud over millions of years under high pressure and temperature. This organic matter, called ancient biomass, turned into crude oil and became stored within rocks. Crude oil is a finite resource. Since crude oil takes millions of years to form, it is a finite resource, it will not last forever. One day, we will use up all the crude oil available, which means that it is a non-renewable source of energy.