Fossil fuels (oil, gas, coal, uranium, and thorium) are found in considerable abundance in widely distributed sedimentary basins on North America (Bally, this volume, Fig. 1); uranium and thorium occur in hardrock, nonbasin areas as well. For the past 100 years, North America’s energy requirements have been met primarily by fossil fuels, and this will probably be true well into the next century. Although one or more of the fossil fuels have predominated at various times, the trend is toward the fuels with greater concentrations of energy per unit volume. This chapter provides an overview of North America’s fossil fuels, including their geographic and geologic distribution, resource volumes, associated problems, and future research related to solving these problems. Various aspects of these fuels are covered in greater detail in other volumes of this series.
Fossil fuel volumes are described in this chapter as identified resources, reserves, and undiscovered resources. Identified resources are those whose location, characteristics, and quantity are known from specific geologic evidence. This category includes resources that could be economically extracted—reserves—and those that are currently uneconomic to extract. Undiscovered resources are those postulated to exist separate from identified resources. The interrelations of these terms are illustrated on Figure 1, a simplified version of the classification and nomenclature scheme designed for all minerals, developed by the U.S. Bureau of Mines and the U.S. Geological Survey (1980). Unconventional resources, a separate resource category not included in Figure 1, but of possible future importance, require extraction techniques different from conventional extraction techniques.