The earth is changing. It is changing before our eyes, and life is changing with it at an ever-faster rate. Awareness of this fact has been slow in coming, because we have always thought of nature as dependable and constant, of the earth as rigid, and of the sea as eternal. We are confused by this new perspective and worried by the many voices that cry danger but seldom offer true solutions.

Yet change is not new in the long history of the earth; it began when the earth began, and has been continuous. It has also often been swift and dramatic, contrary to what geologists have traditionally believed.

These realizations derive from a science of the earth that is itself changing greatly after the adoption, a quarter century ago, of a ruling theory that includes continental drift. This revolution has brought together scholars of many backgrounds, skills, and interests who are learning to understand each other, knowing that otherwise there will be no more progress. Our view of the history of the earth's surface and of all that lived and lives on it is being altered forever by this process.

It is of this eternally changing earth that I write here, in the belief that there are many who, though not professional earth scientists, wish to understand our planet as it is now and are willing to make an effort to learn how it came to its present state.