Fossil fuels are made from decomposing plants and animals. These fuels are found in the Earth’s crust and contain carbon and hydrogen, which can be burned for energy. Coal, oil, and natural gas are examples of fossil fuels. Coal is a material usually found in sedimentary rock deposits where rock and dead plant and animal matter are piled up in layers. More than 50 percent of a piece of coal’s weight must be from fossilized plants. Oil is originally found as a solid material between layers of sedimentary rock, like shale. This material is heated in order to produce the thick oil that can be used to make gasoline. Natural gas is usually found in pockets above oil deposits. It can also be found in sedimentary rock layers that don’t contain oil. Natural gas is primarily made up of methane.