Geomorphology (from Greek: γη, ge, "earth"; μορφή, morfé, "form"; and λόγος, logos, "knowledge") is the study of landforms and the processes that shape them. Geomorphologists seek to understand why landscapes look the way they do: to understand landform history and dynamics, and predict future changes through a combination of field observation, physical experiment, and numerical modeling. Geomorphology is practiced within geology, geodesy, geography, archaeology, and civil and environmental engineering. Early studies in geomorphology are the foundation for pedology, one of two main branches of soil science.
Landforms evolve in response to a combination of natural and anthropogenic processes. The landscape is built up through tectonic uplift and volcanism. Denudation occurs by erosion and mass wasting, which produces sediment that is transported and deposited elsewhere within the landscape or off the coast. Landscapes are also lowered by subsidence, either due to tectonics or physical changes in underlying sedimentary deposits. These processes are each influenced differently by climate, ecology, and human activity.
Practical applications of geomorphology include measuring the effects of climate change, hazard assessments including landslide prediction and mitigation, river control and restoration, coastal protection, and assessing the presence of water on Mars.
Paleogeomorphology is the study of the geomorphology of all or part of the earth's surface at some time in the earth's past.
source : http://en.wikipedia.org/wiki/Geomorphology
Landform :
A landform comprises a geomorphological unit, and is largely defined by its surface form and location in the landscape, as part of the terrain, and as such, is typically an element of topography. Landforms are categorised by features such as elevation, slope, orientation, stratification, rock exposure, and soil type. They include berms, mounds, hills, cliffs, valleys, rivers and numerous other elements.
Oceans and continents exemplify the highest-order landforms. Landform elements are parts of a high-order landforms that can be further identified, such as hill-tops, shoulders and backslopes.
Some generic landform elements are: pits, peaks, channels, ridges, passes, pools, plains; these can be often extracted from a digital elevation model using some automated techniques where the data (various kinds) has been gathered by modern satellites and stereoscopic aerial surveilance cameras. Until recently, compiling the data found in such data sets required time consuming and expensive techniques of "Boots on the ground" at many man-hours. Terrain (or relief) is the third or vertical dimension of land surface. When relief is described underwater, the term bathymetry is used. Topography is a further synonym, and is often illustrated in the form of a contour map.
Elementary landforms (segments, facets, relief units) are the smallest homogeneous divisions of the land surface, at the given scale/resolution. These are areas with relatively homogenous morphometric properties, bounded by lines of discontinuity. A plateau or a hill can be observed at various scales ranging from few hundred meters to hundreds of kilometers. Hence, the spatial distribution of landforms is often scale-dependent as is the case for soils and geological strata.
A number of factors, ranging from plate tectonics to erosion and deposition can generate and affect landforms. Biological factors can also influence landforms— for example, note the role of vegetation in the development of dune systems and salt marshes, and the work of corals and algae in the formation of coral reefs.
Landforms do not include man-made features, such as canals, ports and many harbors; and geographic features, such as deserts, forests, grasslands, and impact craters.
Many of the terms are not restricted to refer to features of the planet Earth, and can be used to describe surface features of other planets and similar objects in the Universe.
source : http://en.wikipedia.org/wiki/Landforms
Diastrophism :
Diastrophism is a general term that refers to deformation of the Earth's crust.
The term covers movement of solid crust material (as opposed to molten material which is volcanism). The movements cause rock to be bent or broken as a result of pressures exterted by plate tectonics or the rise of magma from below.
The most obvious evidence of disastrophic movement can be seen in sedimentary rock where bent, broken or non-horizontal strata provide visual proof of movement. Diastrophic movement can be classified as two types, folding and faulting.
Fold :
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of plastic (i.e. permanent) deformation. Synsedimentary folds are those due to slumping of material before deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales. Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. A set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones.
source : http://en.wikipedia.org/wiki/Fold_%28geology%29
Fault :
In geology, a fault or fault line is a planar rock fracture, which shows evidence of relative movement. Large faults within the Earth's crust are the result of shear motion and active fault zones are the causal locations of most earthquakes. Earthquakes are caused by energy release during rapid slippage along faults. The largest examples are at tectonic plate boundaries but many faults occur far from active plate boundaries. Since faults do not usually consist of a single, clean fracture, the term fault zone is used when referring to the zone of complex deformation that is associated with the fault plane.
The two sides of a non-vertical fault are called the hanging wall and footwall. By definition, the hanging wall occurs above the fault and the footwall occurs below the fault. This terminology comes from mining. When working a tabular ore body the miner stood with the footwall under his feet and with the hanging wall hanging above him.
source : http://en.wikipedia.org/wiki/Geologic_fault
Orogeny :
Orogeny (Greek for "mountain generating") is the process of natural mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within a time frame.
Orogenic events occur solely as a result of the processes of plate tectonics; the problems which were investigated and resolved by the study of orogenesis contributed greatly to the theory of plate tectonics, coupled with study of flora and fauna, geography and mid ocean ridges in the 1950s and 1960s.
The physical manifestations of orogenesis (the process of orogeny) are orogenic belts or orogens. An orogen is different from a mountain range in that an orogen may be completely eroded away, and only recognizable by studying (old) rocks that bear the traces of the orogeny. Orogens are usually long, thin, arcuate tracts of rocks which have a pronounced linear structure resulting in terranes or blocks of deformed rocks, separated generally by dipping thrust faults. These thrust faults carry relatively thin plates (which are called nappes, and differ from tectonic plates) of rock in from the margins of the compressing orogen to the core, and are intimately associated with folds and the development of metamorphism.
The topographic height of orogenic mountains is related to the principle of isostasy, where the gravitational force of the upthrust mountain range of light, continental crust material is balanced against its buoyancy relative to the dense mantle.
Erosion inevitably takes its course, removing much of the mountains, leaving the core or mountain roots, which may be exhumed by further isostatic events balancing out the loss of elevated mass. This is the final form of the majority of old orogenic belts, being a long arcuate strip of crystalline metamorphic rocks sequentially below younger sediments which are thrust atop them and dip away from the orogenic core.
source : http://en.wikipedia.org/wiki/Orogeny
Tectonic uplift :
Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.
Orogenic uplift is the result of tectonic plate collisions and results in mountain ranges or a more modest uplift over a large region. The Himalaya were (and are still being) formed by the collision of two continental plates, the Indian and Eurasian Plates. This ongoing collision produced the Tibetan Plateau as well as the Himalaya and associated ranges. The Ozark Plateau is a broad uplifted area which resulted from the Ouachita Orogeny to the south during the Permian Period. Another related uplift is the Llano Uplift in Texas, a geographical location named after its uplift features. The Colorado Plateau with its spectacular scenic canyons, the Grand Canyon, is also the result of broad tectonic uplift followed by river erosion.
Isostatic uplift includes the gradual uplift following rapid erosional removal of material from a mountain range. The land rises as a result of the removal of the weight. Another example of isostatic uplift is post-glacial rebound following the melting of continental glaciers and ice sheets. The Hudson Bay region of Canada and the Great Lakes of Canada and the United States are currently undergoing gradual rebound as a result of the melting of the ice sheets 10,000 years ago.
In a few cases, tectonic uplift can be seen in the cases of coral islands. This is evidenced by the presence of various oceanic islands comprised entirely of coral, which otherwise appear to be high islands (i.e., islands of volcanic origin). Examples of such islands are found in the Pacific, notably the three great phosphate rocks, Nauru, Makatea, and Banaba as well as Fatu Huku in the Marquesas Islands and Henderson Island in the Pitcairn Islands. The uplift of these islands is the result of the movement of oceanic tectonic plates. Sunken islands or guyots with their coral reefs are the result of crustal subsidence as the oceanic plate carries the islands to deeper or lower oceanic crust areas.
source : http://en.wikipedia.org/wiki/Tectonic_uplift
Volcano :
A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot, molten rock, ash and gases to escape from below the surface. Volcanic activity involving the extrusion of rock tends to form mountains or features like mountains over a period of time.
Volcanoes are generally found where tectonic plates are pulled apart or come together. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by "divergent tectonic plates" pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by "convergent tectonic plates" coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust (called "non-hotspot intraplate volcanism"), such as in the African Rift Valley, the Wells Gray-Clearwater Volcanic Field and the Rio Grande Rift in North America and the European Rhine Graben with its Eifel volcanoes.
Volcanoes can be caused by "mantle plumes". These so-called "hotspots" , for example at Hawaii, can occur far from plate boundaries. Hotspot volcanoes are also found elsewhere in the solar system, especially on rocky planets and moons.
source : http://en.wikipedia.org/wiki/Volcanism
Denudation :
Denudation is the process by which the removal of material, through means of erosion and weathering, leads to a reduction of elevation and relief in landforms and landscapes. Exogenic processes, including the action of water, ice, and wind, predominantly involve denudation. Denudation can involve the removal of both solid particles and dissolved material. Both mechanical and chemical weathering occurs in relation to geomorphological landforms. At present the most significant processes leading to denudation include deforestation (including slash-and-burn practises of local peoples), overgrazing and certain forms of intensive farming which lead to large scale erosion.
Factors affecting Denudation include:
- Surface geography
- Properties of Earth material
- Climate
- Tectonic setting
- Activities of man, animals and vegetation
Erosion :
Erosion is displacement of solids (sediment, soil, rock and other particles) usually by the agents of currents such as, wind, water, or ice by downward or down-slope movement in response to gravity or by living organisms (in the case of bioerosion). There are two different types of erosion "mechanical erosion" and "chemical erosion" Each of these has a different effect on the environment. Mechanical erosion would include water, wind, sun, ice, natural disasters such as earthquakes and shoreline erosion. Chemical erosion would be acid rain, over use of fertilizer, human land use, deforestization and overgrazing.
Erosion is distinguished from weathering, which is the process of chemical breakdown of the minerals in the rocks, although the two processes may be concurrent.
Erosion is an intrinsic natural process but in many places it is increased by human land use. Poor land use practices include deforestation, overgrazing, unmanaged construction activity and road or trail building. Land that is used for the production of agricultural crops generally experiences a significant greater rate of erosion than that of land under natural vegetation. This is particularly true if tillage is used, which reduces vegetation cover on the surface of the soil and disturbs both soil structure and plant roots that would otherwise hold the soil in place. However, improved land use practices can limit erosion, using techniques like terrace-building, conservation tillage practices, and tree planting.
A certain amount of erosion is natural and, in fact, healthy for the ecosystem. For example, gravels continuously move downstream in watercourses. Excessive erosion, however, does cause problems, such as receiving water sedimentation, ecosystem damage and outright loss of soil.
source : http://en.wikipedia.org/wiki/Erosion
Mass wasting :
Mass wasting, also known as mass movement or slope movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, slides, flows, topples, and falls, each with their own characteristic features, and take place over timescales from seconds to years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth, Mars, and Venus.
When the gravitational force acting on a slope exceeds its resisting force, slope failure (mass wasting) occurs. The slope material's strength and cohesion and the amount of internal friction between material help maintain the slope's stability and are known collectively as the slope's shear strength. The steepest angle that a cohesionless slope can maintain without losing its stability is known as its angle of repose. When a slope possesses this angle, its shear strength perfectly counterbalances the force of gravity acting upon it.
Mass wasting may occur at a very slow rate, particularly in areas that are very dry or those areas that receive sufficient rainfall such that vegetation has stabilised the surface. It may also occur at very high speed, such as in rock slides or landslides, with disastrous consequences, both immediate and delayed, e.g., resulting from the formation of landslide dams.
Factors that change the potential of mass wasting include: change in slope angle; weakening of material by weathering; increased water content; changes in vegetation cover; and overloading.
source : http://en.wikipedia.org/wiki/Mass_wasting
Weathering :
Weathering is the decomposition of rocks, soils and their minerals through direct contact with the Earth's atmosphere. Weathering occurs in situ, or "with no movement", and thus should not to be confused with erosion, which involves the movement and disintegration of rocks and minerals by agents such as water, ice, wind and gravity.
Two important classifications of weathering processes exist. Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions such as heat, water, ice and pressure. The second classification, chemical weathering, involves the direct effect of atmospheric chemicals, or biologically produced chemicals (also known as biological weathering), in the breakdown of rocks, soils and minerals.
The materials left over after the rock breaks down combined with organic material creates soil. The mineral content of the soil is determined by the parent material, thus a soil derived from a single rock type can often be deficient in one or more minerals for good fertility, while a soil weathered from a mix of rock types (as in glacial, eolian or alluvial sediments) often makes more fertile soil.
source : http://en.wikipedia.org/wiki/Weathering
Water cycle :
The Earth's water is always in movement, and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Since the water cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice at various places in the water cycle, with these processes happening in the blink of an eye and over millions of years. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go in a hurry.
source : http://en.wikipedia.org/wiki/Hydrologic_cycle
Climate :
Climate, (from Ancient Greek klima) is commonly defined as the weather averaged over a long period of time... The standard averaging period is 30 years but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations.
The main difference between climate and everyday weather is best summarized by the popular phrase "Climate is what you expect, weather is what you get." Over historic time spans there are a number of static variables that determine climate, including: latitude, altitude, proportion of land to water, and proximity to oceans and mountains. Other climate determinants are more dynamic: The thermohaline circulation of the ocean distributes heat energy between the equatorial and polar regions; other ocean currents do the same between land and water on a more regional scale. Degree of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric greenhouse gases determines the amount of solar energy retained by the planet, leading to global warming or global cooling. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned.
source : http://en.wikipedia.org/wiki/Climate
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