Crude oil, or oil in the ground, is thick and dark brown or black. It is a mixture of various hydrocarbons, and can form from dead organisms buried in the ground. Heat and pressure from layers over fossils creates liquid oil.
To produce petroleum, crude oil must be trapped between a porous rock layer and an impermeable layer. Oil companies drill into the porous rock to extract crude oil from it. Then, to separate the different types of hydrocarbons, crude oil must be refined in factories.
Oil is mainly used as fuels, such as gasoline, diesel, and heating oil. It is rich in energy and easily transported. The remaining compounds from oil are used to make waxes, plastics, fertilizers, and other products. In cars, gasoline burns, causing the pistons to move; this powers the vehicle.
Oil spills, such as the 2010 BP spill in the Gulf of Mexico, occur regularly. In addition, oil is not a renewable resource, and will run out eventually.