Some of the planet's most destructive forces—including earthquakes and volcanic activity—are caused by the same factors that helped shape much of the Earth as it is today. Plate tectonics, or movement of the Earth's outer layers, can occur in a number of different ways and produce a range of results, some minor and others far more considerable or devastating. Distinct maps, interesting sidebars, and annotated illustrations of the Earth's layers are included in this volume, which details the motion of the planet and the nature and study of both earthquakes and volcanoes.