The micro-organisms didn't completely decompose because there wasn't enough oxygen in the water.
Later, sediments covered them.
Crude oil comes from that organic matter.Crude oil is a mixture of hydrocarbon molecules,
for example "octane" (C8H18)
Hydrocarbon molecules are hydrogen atoms and carbon atoms linked together in "chains" of different lengths. For example, octane has a "length" of eight carbon atoms.
Consequences Of Crude Oil :(
If crude oil falls to the water the light wont pass through it and plants and animals will die.
<---------- like you see in the picture this duck is completely covered by crude oil.
Distillation: To separate molecules of different lenghts, we pass oil through a hot pipe.
As the oil get hot, the lighter molecules evaporate and exit the pipe.
As the oil gets hotter, longer (and heavier) molecules evaporate, and only the heaviest
molecules exit at the end of the pipe.