In addition to 700 cross-referenced entries, Kusky (natural sciences, St. Louis U.) presents 19 essays, interspersed throughout the text which discuss topics such as the formation of Earth and the solar system, life on Mars, coping with the sea level rise in coastal cities, and earthquake warning systems. Entries are arranged alphabetically and range in length from 100 to 2,500 words. They cover concepts, theories and hypotheses, places, events, the major periods of geological time, history, technology, organizations, and people who have made significant contributions to the field. Specific topics include strike-slip fault, terminal moraine, tsunami, weathering, Yellowstone National Park, mass wasting, Kaapvaal craton, ichnofossils, greenstone belts, geodesy, El Niñ>o, desalination, carbon cycle, and aa lava. Five appendixes contain the periodic table of elements, the geologic time scale, classification of species, solar system data, and evolution of life and the atmosphere. This encyclopedia is intended to be a reference for high school and college students, teachers and professors, researchers, and general readers.