Throughout this book, we have mentioned human use of Earth materials, most of which are nonrenewable. Our purpose in this chapter is to survey briefly some important geologic resources of economic value.

We first look at energy resources to see which ones might help replace our disappearing supplies of oil. Then we discuss metals and their relation to igneous rocks and plate tectonics and conclude with nonmetallic resources such as sand and gravel.

Expanded Readings From Chapter 21

Flammable Ice Solution to Energy Shortage or Major Contributor to Global Warming