What we often call oil is called petroleum or crude oil. It comes in liquid, gas, and tar form. Once it is extracted from the earth, it can be refined into gasoline, jet fuel, and petrochemicals. Gasoline is what powers our cars, and jet fuel powers our planes. Plastics, pharmaceuticals, and cleaning products all use petrochemicals made from refined petroleum.

Crude oil is found deep underground within rock layers. It exists as pockets within rocks rather than as a giant pool that can be sucked up. Oil companies access these pockets of oil by using drilling rigs or oil wells. The rigs and wells pump out oil from pockets within rock layers. An excellent example of how oil rigs and wells work is to think of a sponge. The sponge is the rock layer that has crude oil inside. Oil rigs and wells pump out the oil and gas contained within the sponge.

Petroleum is a cleaner fossil fuel than coal. However, it still has negative environmental effects. The production of petrochemicals from petroleum generates air pollution. Gasoline burned by cars creates emissions that can lead to global warming. Oil spills such as the Deepwater Horizon spill in 2010 can cause catastrophic damage to the environment and impact people’s livelihoods.

Natural gas is a fossil fuel that has gained much attention lately because it is a relatively inexpensive and clean-burning fossil fuel. A large amount of natural gas is now produced using hydraulic fracturing. Fracking, a common term for hydraulic fracturing, involves blasting rocks with chemicals, sand, and water at very high pressure. The high pressure and chemical, sand, and water mixture cracks open or fractures the rocks and lets oil and gas companies extract the natural gas to the surface.

There are undesirable effects from fracking. The chemicals and sand used in the fracking process are left behind in the rocks. This can contaminate groundwater and lead to unstable bedrock. Some scientists believe that fracking can even lead to earthquake activity.

Besides natural gas and oil found deep underground within rocks, other sources of crude oil can be extracted. These sources include tar sands and oil shales. Tar sands are sands that are mixed with a hydrocarbon substance called bitumen. Extracting petroleum from tar sands comes with a high environmental cost in the form of habitat destruction and the creation of toxic waste during the refining process. Oil shales are rocks that contain a substance called kerogen, which is similar to crude oil. The production of crude oil from oil shales is expensive and uses a large amount of water, so crude oil production from oil shales is limited.