Throughout this book, we have mentioned human use of Earth materials, most of which are nonrenewable. Water is a resource that is an important exception. It is renewable and was discussed separately in Chapters 16 and 17. 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.