Fossil fuels are the result of millions of years of heat and pressure transforming organic matter – such as plants, bacteria, and animal tissue – into coal, oil, or gas. Fossil fuels aren’t literally fossils – bones and shells aren’t a great source of energy – but the oil and gas deposits we rely on today date back to the age of the dinosaurs, more than 65 million years ago. As a result, most of these deposits are found underground, in sedimentary rock or tar sands, and they require significant efforts to find and extract. Fossil fuels aren’t distributed evenly, so some areas are more abundant in fossil fuels than others. According to the Energy Information Administration, 32 states produce crude oil, but Texas accounts for more than 42% of U.S. crude oil production. In terms of world energy production, the U.S. produces the most gas and oil, while China produces the most coal. Since fossil fuel deposits are often located far from the regions they supply, pipelines may be used to transport fossil fuels from one region to another, creating more potential environmental hazards, such as leaks and spills during transport.