Over 7,500 entries The fourth edition of this leading geology dictionary contains over 7,500 clear and concise entries on all aspects of geology and earth sciences, including planetary science, volcano-logy, paleontology, and mineralogy. Over 130 line drawings complement the definitions and useful appendices include a revised geological time scale, stratigraphic units, lunar and Martian time scales, wind-strength scales, and SI units. Fully revised and updated, with over 150 new entries and numerous web links, this is the ideal reference for students of geography, geology, earth sciences, and related disciplines.