Glossary of Geological Terms - Article Example

Glossary of Geological Terms Alluvium – Alluvium is a deposit/sediment that consists of soil particles, sand, leaves and organic matter. It is deposited by streams, rivers or other forms of flowing water. It is most widely formed in the lower part of the course of a river, but may also be found at points on the bank where a river overflows or where the velocity of a river is modified – for instance, whenever the river flows into an ocean. In the lower parts of a river where it is formed, it forms floodplains and deltas. It also gives rise to very fertile soil. 1. http://www.answers.com/topic/alluvium-or-alluvion 2. Backshore – Backshore is that part of a beach landscape that extends landward from the sloping foreshore till the landscape changes to either developed land or vegetation. The profile or the physical forms of the backshore depend on the tide patterns and the seasonal changes to the environment. The faunal and floral composition of the backshore area usually also varies. It is set apart from the often barren foreshore by a marked increase in biodiversity. 2.http://earthsci.org/education/teacher/basicgeol/ocean/ocean.html 3. Clay – Clay is a building material of sorts. The term Clay does not refer to one discrete material but to a number of earthy materials composed of silica, Alumina, water and other minerals. Before the development of X-ray diffraction, it was difficult to tell what exactly Clay was composed of, because the particles that make up Clay are very fine. The properties of Clay tend to vary with the addition of water and its varying compositions. Depending on the water content, Clay can be either plastic or very hard. 3. http://www.dep.state.fl.us/geology/geologictopics/rocks/common_clay.htm 4. Desertification – Desertification is a very gradual process, usually spanning a couple of years, whereby productive land that is suitable for many types of vegetation is converted to non-productive, arid land. Many factors cause this transition, but human activities and climate changes are often cited as the primary reasons for desertification. Desertification leads to a major loss of biodiversity. As a result, the ecosystem of the geographic area as well as that of surrounding areas might be affected. Desertification poses one of the greatest environmental threats today. 4.http://www.icarda.org/HomePageStory/Desertification.htm 5. Erosion – The wearing away of soil, rock and other particles from a natural/man made structure is called erosion. Erosion is caused by several factors which are individually referred to as the ‘energy for erosion’. Solar radiation, rainwater, the motion of air as a result of pressure differences, etc are all examples of factors that cause erosion. Erosion is responsible for the formation of hills and valleys. There are three stages in the erosion process: detachment, entrainment and transport. 5. http://www.fao.org/docrep/T1765E/t1765e0c.htm 6. Fault – A fracture between two rocks that are relatively displaced is termed as a fault. This means or shows that blocks/rocks have moved or have been displaced relative to one another. There are many different kinds of faults that are categorized according to their relative positions and direction of displacement. Some examples of faults found in the earth’s crust are Dip-slip faults, Fault trace, Fault creep, Strike-slip fault, Normal fault, Reverse Fault, etc. 6.http://soundwaves.usgs.gov/2009/11/fieldwork2.html 7. Glacier – A moving body of snow that is formed by the gradual accumulation of snow is known as a glacier. Glaciers have the tendency to grow as a result of gathering more snow as they move and recrystallization. It has the ability to survive through the summer season and to grow each year. Many claim that the rapid melting of glaciers formed over millions of years will cause sea levels to rise all over the world, posing a direct threat to low-lying countries. There are two kinds of Glaciers: Valley glaciers and Continental Glaciers. They are distinguished on the basis of their movement patterns; Valley glaciers tend to move down a slope due to the gravitational pull on their mass and continental glaciers tend to flow outwards from a thick central area under the influence of their own weight. 7. http://www.eoearth.org/article/Glacier 8. Hydrologic Cycle - The hydraulic cycle defines the movement of water from the earth into the atmosphere, and then from the atmosphere back into the earth. This movement is controlled by subsurface conditions encountered. The various processes that are described in this cycle are evaporation (from man-made and natural resources), transpiration (from plants), percolation, infiltration, run-off, condensation, precipitation, etc. 8. Image http://pubs.usgs.gov/gip/gw_ruralhomeowner/gw_ruralhomeowner_new.html Hydrologic Cycle 9. Igneous Rock – Crystallization and solidification of molten magma leads to the formation of igneous rock. Magma itself is formed by the extreme heating of rock at very high temperatures under the surface of the Earth. Igneous rock is found in many forms. Variations are found due to three factors: the chemical composition of the magma, the temperature at which it solidifies, and the rate at which it cools, which affects the crystallization process. For instance, quick cooling causes the crystals that are formed to be very small and fine. Examples of igneous rock are Andesite, Basalt, Diorite, Gabbro, etc. 9.http://geology.com/rocks/diorite.shtml 10. Joint – A plan surface or fracture or parting in a rock without displacement is called a joint. This is as opposed to a fault, where displacement has taken place. It is present nearly in all kinds of rocks, and it extends in almost all directions. The primary reason for the formation of joints in rocks is crustal movement, contraction upon consolidation of sediment, crystallization, expansion and intrusion also contribute to minor jointing in rocks. Different kinds of joints include transition joints, dip joints, oblique joints, etc. 10. http://earthsci.org/processes/pro.html 11. Karst – Karst is a topographical setting. It is a landscape formed from the decomposition and dissolution of soluble rocks. The landscape is characterized by sinkholes, caves and underground drainage systems. One of the major reasons for the formation of a Karst is acid rain – when carbon dioxide comes into contact with rainwater, it speeds up erosion of soil (Limestone, in particular) once the water is absorbed by the ground. This leads to the formation of underground channels and caves, which are susceptible to collapse from the surface. 11. http://www.esi.utexas.edu/outreach/caves/karst.php 12. Limestone – Limestone is a sedimentary rock that is composed mainly of Calcite (or Calcium Carbonate). A major portion of the composition of limestone is comprised of the skeletal fragments of marine organisms such as coral. Limestone is used as a raw material in many industries. It is obtained by either the precipitation of Calcite in dissolved in water and deposition of marine organisms and entrainment of secondary minerals. It is a very important part of several ecosystems. 12. http://geology.com/rocks/limestone.shtml 13. Magma (Rock) – Magma is the hot molten material from which igneous rocks are formed. It is composed mostly of silicates, carbonates and sulfide liquids that have melted under high temperatures. Magma is formed due to the extremely high temperature and pressure conditions beneath the Earth’s crust. When it leaks out through cracks in the surface, it cools down to form igneous rock. There are several factors that determine the properties of Magma, and they are interrelated. They include chemical composition, viscosity, dissolved gases and temperature. 13. http://onemansblog.com/wp-content/uploads/2007/03/LiquidHotMagma.jpg 14. Nappe – A Nappe is described as a fragment of a rock that has been displaced far from it original position. The rock in its original position is referred to as Autochthonous rock and the displaced rock is referred to Allochthonous. The displacement usually results as a cause of faulting or folding. In cases where erosion cuts through the nappe, two formations can result: the fenster, in which the younger underlying rock is exposed and surrounded by the older rock, or the klippe, in which the older rock is surrounded by the younger rock. 14. http://www.sfakia-crete.com/forum2/read.php?5,2425,2622 15. Ore Mineral – A rock that contains a high enough concentration of an element for it to be usefully and easily extracted is called an Ore Mineral. Most useful mineral are obtained through extraction from their ores. There are many ways to concentrate the element into an ore. These include dissolution of the element by hot water, preferential crystallization by magma, surface weathering or leaching and through erosion. 15. http://earthobservatory.nasa.gov/Features/ASTERProspecting/ 16. Plate Tectonics – Plate Tectonics is a theory that states that the lithosphere is composed of moving plates. This theory is based on several evidences, some of which are listed as follows: Similar fossil occurrences on different continents, jigsaw-like profiles of some continents, similar geologic deposits of rocks on two different continents, etc. Subsequent research over the years has found that the earth is composed of a number of oceanic and continental plates that float on the asthenosphere. 16. http://www.eoearth.org/article/Plate_tectonics 17. Quarrying – Quarrying is one of the easiest, most economically viable methods. Quarry is a mine surface that is used to extract and mine rocks and other elements. The elements that are obtained through this method (sand, gravel and aggregate material) are used for building purposes and are also referred to as construction stone. Hence, quarrying can be defined as the method through which minerals and elements are extracted from quarries. 17. http://www.uky.edu/KGS/im/limestone.htm 18. Rock Cycle – The rock cycle is a model that postulates a theory about how rocks are formed and influenced through and by various physical and chemical processes and transitions. This theory opens up the possibility that the origin of all rocks can be traced back to the cooling and solidification of magma. It is an established fact that all kinds of rock can be physically and chemically broken down by various surface processes known as weathering. Rock cycle is important in recording and unraveling the earth’s history in the universe. 18. http://www.eoearth.org/article/Rock_cycle?topic=50013 19. Sedimentary Rock – Sedimentary rock is formed from particles of pre-existing rocks and pieces of other dead organisms. These particles are washed away and accumulate at the bottom of lakes, rivers and oceans. Eventually as they are pressed down, they begin to transform due to extremely high pressure and temperature conditions. They subsequently form sedimentary rock. Sedimentary rocks are categorized into three different classes: clastic, chemical, and organic. These different kinds are further divided into subclasses. They differ in terms of composition and by what process they have been formed. 19. http://www.energyinst.org.uk/education/glossary/ 20. Topography – Topography is a very crucial term in all the different fields of geosciences. It refers to the physical and geographical profile of an area – that is, the shape and size of the earth’s surface in a certain area. Topography is affects and is affected by the climate. It tends to vary with altitude. Vegetation varies too with different kinds of topography. Topographic data is important for various kinds of fields. – Civil engineering, exploration, etc. 20. http://www.eoearth.org/article/Topography?topic=49460 21. Unconformity – Unconformities result when there is a discontinuous deposition of sediment taking place. They are ancient surfaces that have been eroded before the eroded particles are buried underneath layers of sediment deposition. Basically, any gap or crack in the sedimentary history of a rock is considered or termed as an unconformity. There are three kinds of unconformities: Nonconformity, angular unconformity and disconformity. An example of an unconformity is the Great Unconformity in the Grand Canyon. 21. http://www.geol.umd.edu/~jmerck/arizonasite/imagepages/unconformity.html 22. Volcanism – The process, by which hot, molten rock material, or magma, oozes out of the surface of the earth, releasing toxic gases associated with it in the process in to the air, is known as volcanism. Volcanism usually occurs in specific geologic settings. Active volcanoes can be found where two lithospheric plates converge and slightly overlap. One plate overrides the other, pressing it down to its mantle layer. Active volcanoes are also found along the axis of the oceanic ridge system (where both plates move alongside the axis and magma rises up from the mantle). 22. http://www.geology.wisc.edu/courses/g115/volcano/main2.html 23. Watershed – A watershed is an area that separates two adjacent, discrete flowing water systems. It is usually where running waters joins a stream or a river. It is also called a drainage basin. On a topographic mark, it can be highlighted by tracing the points of highest elevation, which are usually ridge crests located between two adjacent streams or bodies of flowing water. There are three hydrological kinds of watersheds: Exorheic watershed, Endorheic watershed and Arheic regions. They are categorized on the basis of where the discharge of one body of water into another body of water is taking place. 23. http://water.epa.gov/type/watersheds/whatis.cfm 24. Xenolith – Xenolith is a small fragment encased in an intrusive igneous body that is not related to the igneous body in itself. They arise when pieces of metamorphically transformed rock fall into molten lava while it is cooling. These can be quite big in size and are usually found in clusters. They can be regained through the process of contact metamorphosis, whereby heat and fluids are utilized to cause mineralogic and chemical changes in the parent rock of the xenolith. 24. http://ericfdiaz.webs.com/igneous_rock.htm 25. Yardang – Largely a result of wind erosion, Yardangs are areas of soft, weakly agglomerated rock and bedrock surfaces that have been subject to extensive weathering and hence have been fluted, pitted and grooved. It is often oriented parallel to the direction of the wind. Yardangs are found in many deserts all over the world. Examples are found in the deserts of Turkistan and the Mojave deserts. 25. http://georneys.blogspot.com/2011_05_01_archive.html 26. Ziolites – The Ziolite rocks are a group of basic and hydrated, aluminosilicate minerals. They have an open aluminosilicate structure that is filled with water channels and cations. There are about 45 different kinds of zeolites. Zeolites easily lose and regain their water of hydration. They also tend to fuse and swell when subject to very high temperatures. Zeolites exhibit wide compositional differences, even within the same species. They form an integral part of some ecosystems. 26. http://www.chemistryexplained.com/Va-Z/Zeolites.html#b Works Cited Saklani, P.S. Glossary of Structural Geology and Tectonics. Satish Serial Publishing House, Delhi. Encyclopedia Britannica. Alluvium [Online]. Available from http://www.britannica.com/EBchecked/topic/16665/alluvium [Cited 3 March 2012]. Hogan, C. M., Baum, S., and Saundry, P. 2010. Backshore [online]. Available from http://www.eoearth.org/article/Backshore?topic=49523 [Cited 3 March 2012]. 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Available from http://www.chemistryexplained.com/Va-Z/Zeolites.html#b [Cited 3 March 2012]. Read More