Description The image of the Earth on the front cover was acquired from the GOES-8 Imager by the Laboratory for Atmosphere at NASA'S Goddard Space Flight Center, Greenbelt, MD. It was taken on September 2, 1994, using two channels for the Imager to produce a "natural color" effect. The photos shown here on the back cover illustrate the four spheres of the Earth system - the atmosphere, biosphere, hydrosphere, geosphere - together with changes being produced by human activities. Table of Contents THE EARTH IN SPACE. The Earth System. Fellow Travelers in Space: Earth's Nearest Neighbors. The Sun, Giver of Life. THE EARTH BENEATH OUR FEET. Plate Tectonics. Earthquakes and the Earth's Interior. Minerals and Rocks. The Heat Within: Magmas and Volcanoes. The Earth's Evolving Crust. THE EARTH'S BLANKET OF WATER AND ICE. Water on the Land. The World of Snow and Ice. The World Ocean. THE EARTH'S GASEOUS ENVELOPE. Composition and Structure of the Atmosphere. Winds, Weather, and Deserts. The Earth's Changing Climate. A Planetary Perspective on Life. Geochemistry and Life. Biological Evolution and the History of the Biosphere. LIVING ON THE EARTH. Resources from the Earth. The Changing Face of the Land. Global Change: A Planet Under Stress. Appendices. Glossary. Credits. Index.