Similar to oil, natural gas is formed from buried
plankton, but also from coal in late stages of
breakdown. The creation of natural gas, however,
requires higher temperatures than oil.

Coal is formed from fossilized plants. As the plants
get buried deeper and deeper underground they
become subjected to intense heat.

Oil is formed from buried plankton. As sediment
accumulates on top of the fossilized plankton over
the millennia, intense heat flow from the depths
of the earth transform the plankton into oil.