EARTH SCIENCES

Introduction The term Earth Science is used to describe all the sciences concerned with the origin, evolution, structure and the behaviour of the Earth and its place in the universe, especially in the solar system. The study of earth sciences may be grouped into five major categories: 1. The study of the (rocky) part of the Earth: Geology, the most well-Known of the earth sciences belongs to this category; 2. The study of the aqueous part of the Earth: Oceanography, hydrology, glaciology, limnology constitute this group; 3. The study of the gaseous outer regions of the Earth: Atmospheric science including meteorology (weather, meteorology, climatology), and aeronomy that deals with the outermost ionised part of the atmosphere fall in to this category; 4. The study of the biosphere: Biosphere embodies all life on the earth. It includes also zoology, botany and ecology which, however, are distinctive science in their own rights; and 5. The study of the Earth in its entirety:this is the domain of geography which is study of spatial variation of the earth?s surface and of humankind?s relationship with its environment. The distinctiveness of geography lies in the fact that it is the convergence of physical and biological sciences (physical geography) and social sciences, such as, history (historical geography), political science (political geography), and economics (economic geography). A great deal of overlap, however, exists among these categories. Since the International Geophysical Year (IGY) in 1957, there is a trend toward the integration of these categories. The integration of the geo-sphere, biosphere systems is a case in point. In a way, even geology may be defined as the study of Earth itself and many components of other categories may be brought under it. Physical geology and physical geography also share many common elements The deployment of earth-observing devices on satellites, both in geostationary and in low earth orbit, has revolutionized such branches