Derived from Greek words geo (meaning Earth) and logos (meaning knowledge), geology is the science which deals with the origin, composition, structure and history of the Earth and its inhabitants as recorded in the rocks, and the natural forces which operate to change it. Geologists are scientists who study the Earth and by piecing together the history of rock formation and mineral deposits, provide clues to the Earth's development. Geologists study the whole Earth, but they deal especially with minerals, rocks, fossils and ores : how they are formed, what changes they undergo, and the geological history they have to tell. Rocks may appear to be inert and unchanging but each rock carries within it a record of how it was formed and what changes it has undergone. When studying the Earth, geologists ask questions such as: How old is the Earth? How was it formed? Of what is it made? To answer these questions, geologists study the evidence of events that occurred millions of years ago. They then must relate their findings to the results of similar events that are happening today. Geologists assume that the agents of change, wind, rain, waves, rivers and volcanoes, affected the surface of the Earth in the past just as they do today. This is why geology is often referred to as the science of a changing Earth. Those who imagine that geology is primarily concerned with the description and classification of rocks will be surprised to learn about the highly specialised nature of geology and the diversity of interests within it. In studying the Earth. geologists rely heavily on other basic sciences such as chemistry, physics, biology, zoology, botany and astronomy. Geology has two major divisions as outlined in Table 1 - physical geology, and historical geology. Physical geology deals with the Earth's composition, it's structure, the movements between different parts of the Earth's crust, and the processes (such as volcanism and erosion) by which the Earth's surface changes. Historical geology looks at the present nature of the Earth, its evolution through time, and the evolution of plants and animals on Earth. It is thus possible to reconstruct relations of ancient land and seas, and organisms that inhabited them. The goals of geology are directed towards understanding natural earth
processes and the landscapes which result from them, as well as unravelling the evolution
of Earth and the planets through their long history and comprehending the vastness of
geologic time. APPLICATIONS OF GEOLOGY The most important applications of the science of geology to the aims and needs of our society are in the development of natural earth resources, and ecological and environmental protection. Earth's resources have been exploited by humans since before the rise of early civilisation. Geologists study the composition of the rocks and minerals forming the Earth's crust and attempt to locate the natural resources which modern civilisation depends on, i.e. mineral deposits, fossil fuels and groundwater. This is the main economic application of geology. Geologists play a key role in the exploration for and development of economic deposits of rocks, minerals and fuels. Various methods including chemical and geophysical means are used in exploration for these resources. Another important application of geology is in assessing the effects that the human civilisation and the physical environment have on each other, that is, environmental protection. The need to understand our environment is very clear and geology is having an increasing role in land-use planning; environmental monitoring, e.g. assessing the damage and pollution caused by mining activities or to groundwater; engineering investigations to assess and select sites for dams, roads, bridges, buildings; and conservation of soil, water, energy, and other earth resources. Today, people are beginning to appreciate their dependence on a finite world that geological processes helped to form and efforts are being made to conserve the land or to use it more effectively. Exploitation of mineral and other natural resources quickly removes the end products of geological processes that required millions of years to form. Exploitation of these resources (e.g. mining) cannot be stopped, but it can be made more efficient so that minimum damage is sustained by the environment. It is also essential that we learn more about the Earth and the operation of natural systems in order to evaluate the hazards that exist naturally and those that are caused by human activities. This knowledge can help us to reduce economic and human losses caused by these natural disasters over which we have little or no control, such as landslides, floods, volcanic eruptions, and earthquakes. We can also reduce the cost and increase efficiency in managing those natural processes over which we do have control. An understanding of geology can lead to a deeper awareness of one's physical environment and the beauty of nature. It can lead to an understanding of the sometimes violent, awesome and damaging geological events such as earthquakes and volcanic activity. GEOLOGY AND OUR HISTORY The Earth's crust is a rich storehouse of valuable minerals and fossil fuels which have been of great importance to humans since the dawn of human history. In the early Stone Age, people began to make tools out of flint and obsidian (volcanic glass). About 10 000 years ago they discovered how to make copper implements (the Copper Age). About 5000 years later, they found out how to make bronze from copper and tin (the Bronze Age). The invention of bronze, an alloy harder than copper, marked the end of the Stone Age. Even more important was the discovery, about 3300 years ago, of how to work iron, a tough metal more common than copper and tin. The Iron Age marked the start of modern times. Since then, we have gone through the Steel Age and are now in the Atomic Age. At each step, earth materials assumed progressively greater importance. EARTH RESOURCES Today earth resources play a role in our lives second only in importance to agriculture, and of course, plants too use minerals from the soil. We use the various materials of the Earth in thousands of ways. Mining and quarrying furnish the raw materials for many industries. Minerals are an important source of elements which are used in every facet of our lives. For example, metallic minerals produce aluminium for cans and cooking pots, copper for electrical cables, lead and zinc for batteries, tungsten for electric light bulbs, numerous metals for cars and alloys of iron and many other metals for steel. Fossil fuels (petroleum, natural gas, coal, oil shale and gas) are our main source of energy. Non fossil fuels such as uranium are used in nuclear fission reactors to generate electrical power. In addition, various non-metallic or industrial rocks and minerals are used in the form of sand and gravel, crushed rock, brick, tile, plaster, insulation, glass, chinaware, fertilisers, structural materials, abrasives, lubricants, fillers and chemicals. Building stones such as sandstone, limestone, marble, granite and slate are also of considerable importance. People have always been fascinated by the beauty of minerals, and they have been used in jewellery since the Stone Age. Valuable metals used in jewellery include gold, silver and platinum. Gold is the most important because it is easy to work and does not tarnish like silver. Gold mining at Vatukoula is a major industry in Fiji. Valuable minerals (gemstones) include diamonds, rubies, sapphires and emeralds. These four minerals are hard (and hence long-wearing), transparent, and sparkle magnificently when cut and polished. Other minerals used in jewellery include garnet, quartz, topaz, turquoise, zircon, agate, chalcedony, jadeite and opal; these are known as semi-precious gemstones. Organic substances used in jewellery include amber, coral, ivory, jet (a kind of coal) and pearls; none of these are minerals. The list of earth resources that we use is almost endless and the demand for them rises steadily as the world's population and standard of living increases. Table 1. The Earth Sciences.
SUGGESTIONS FOR FURTHER READING Allison, I. S. & Palmer, D. F. 1980. Geology, the science of a changing Earth. VII Edition. McGraw-Hill Inc. Clark, I. F. & Cook, B. J. 1983. Perspectives of the Earth. Australian Academy of Science, Canberra, Australia. Lye, K. 1979. Minerals and Rocks (Kingfisher Guides), Ward Lock Ltd., London. Matthews, W. H. 1970. Geology Made Simple. Made Simple Books, W. H. Allen, London. Press, F. & Siever, R. 1982. Earth, Third Edition. W. H. Freeman & Co. USA. Spencer, E. W. 1983. Physical Geology. Addison-Wesley Publishing
Company Inc., USA.
ISSN 1016-2135 |
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