earth's crust The outer layers of the Earth's structure, varying between 6 and 48 km in thickness, and comprising all the material above the Mohorovicic Discontinuity (a seismic discontinuity occurring between the crust of the earth and the underlying mantle; the discontinuity occurs at an average depth of 35 km below the continents and at about 10 km below the oceans). The earlier idea of a cool solid skin overlaying a hot molten interior has now been replaced by a concept of a crust composed of two shells: an inner basic unit composed of sima (oceanic crust) and an outer granitic unit composed of sial (continental crust)
earth science The science that deals with the earth or any part thereof; includes the disciplines of geology, geography, oceanography and meteorology, among others
Earth-Sun relationship The Earth depends on the sun for its existence as a planet hospitable to life, and solar energy is the major factor determining the climate. Hence, conditions on the sun and conditions on Earth are inextricably linked. Although the sun's rays may appear unchanging, its radiation does vary. Many scientists suspect that sunspot activity has a greater influence on climatic change than variations attributed to the greenhouse effect
