This chapter moves into the field of geology to understand the origins of fossil fuels, or the materials from which we produce energy. Over millions of years, the ocean floor collected the remains of small dead animals. In time, those remains sunk into the ground, fossilized, and created materials such as crude oil. Thanks to plate tectonics, some of what was once seafloor has become land, meaning oil is available even on inland. The same holds true for ancient forests, whose decomposed remains mixed into the ground and, after millions of years, produced coal: “Coal, oil, and natural gas are the pressed, cooked, and cracked remains of the plants and animals (but mostly plants) that lived hundreds of millions of years ago” (103). When extracted and set on fire inside power plants, they produce energy (plastic products are another important product of oil).

Globally, energy resources are derived from 40% oil, 30% coal, and 30% natural gas. At the current rate of global consumption, oil and natural gas supplies will last only another 50 years, with coal lasting another 150 years. Because the Earth creates fossil fuels over millions of years, they are called nonrenewable resources.