A simple introduction to geology, for teen agers and the adults who need to answer their questions. Although there is nothing strikingly new in this, the clear, simple organization and straightforward exposition make it readable, and there has long been a need of a book of this type, for this age. There are chapters on the origin of the earth, the forces that have built up and changed the earth's surface, minerals, origin of plant and animal life, the ice age, etc. Here and there the author is a bit too sure of his answers, surer than are the scientists on whom he draws. His account of the origin of the earth, for example, is only one of many hypotheses- and not the most favored one at that. But by and large, this book will serve well as an introduction to an interesting field.