1.
Geomorphology
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Geomorphology is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near the Earths surface. Geomorphologists work within disciplines such as geography, geology, geodesy, engineering geology, archaeology. This broad base of interests contributes to many styles and interests within the field. Earths surface is modified by a combination of processes that sculpt landscapes, and geologic processes that cause tectonic uplift and subsidence. Many of these factors are strongly mediated by climate, the broad-scale topographies of the Earth illustrate this intersection of surface and subsurface action. Mountain belts are uplifted due to geologic processes, denudation of these high uplifted regions produces sediment that is transported and deposited elsewhere within the landscape or off the coast. On progressively smaller scales, similar ideas apply, where individual landforms evolve in response to the balance of additive processes, often, these processes directly affect each other, ice sheets, water, and sediment are all loads that change topography through flexural isostasy. Topography can modify the climate, for example through orographic precipitation. Many geomorphologists are particularly interested in the potential for feedbacks between climate and tectonics, mediated by geomorphic processes, in addition to these broad-scale questions, geomorphologists address issues that are more specific and/or more local. Fluvial geomorphologists focus on rivers, how they transport sediment, migrate across the landscape, cut into bedrock, respond to environmental and tectonic changes, and interact with humans. Soils geomorphologists investigate soil profiles and chemistry to learn about the history of a landscape and understand how climate, biota. Other geomorphologists study how hillslopes form and change, still others investigate the relationships between ecology and geomorphology. Because geomorphology is defined to comprise everything related to the surface of the Earth and its modification, geomorphologists use a wide range of techniques in their work. These may include fieldwork and field data collection, the interpretation of remotely sensed data, geochemical analyses, geomorphologists may rely on geochronology, using dating methods to measure the rate of changes to the surface. Practical applications of geomorphology include hazard assessment, river control and stream restoration, planetary geomorphology studies landforms on other terrestrial planets such as Mars. Indications of effects of wind, fluvial, glacial, mass wasting, meteor impact, tectonics and this effort not only helps better understand the geologic and atmospheric history of those planets but also extends geomorphological study of the Earth. Planetary geomorphologists often use Earth analogues to aid in their study of surfaces of other planets, other than some notable exceptions in antiquity, geomorphology is a relatively young science, growing along with interest in other aspects of the earth sciences in the mid-19th century. This section provides a brief outline of some of the major figures
2.
Groundwater
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Groundwater is the water present beneath Earths surface in soil pore spaces and in the fractures of rock formations. A unit of rock or a deposit is called an aquifer when it can yield a usable quantity of water. The depth at which pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from, and eventually flows to, the naturally, natural discharge often occurs at springs and seeps. Groundwater is also withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earths subsurface contains some water, Groundwater may not be confined only to Earth. The formation of some of the landforms observed on Mars may have influenced by groundwater. There is also evidence that water may also exist in the subsurface of Jupiters moon Europa. Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water, therefore, it is commonly used for public water supplies. For example, groundwater provides the largest source of water storage in the United States. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, many municipal water supplies are derived solely from groundwater. Polluted groundwater is less visible, but more difficult to clean up, than pollution in rivers, Groundwater pollution most often results from improper disposal of wastes on land. An aquifer is a layer of substrate that contains and transmits groundwater. When water can flow directly between the surface and the zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are more saturated since gravity causes water to flow downward. The upper level of this layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone, substrate with low porosity that permits limited transmission of groundwater is known as an aquitard
3.
Water table
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The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water, the water table is the surface where the water pressure head is equal to the atmospheric pressure. It may be visualized as the surface of the materials that are saturated with groundwater in a given vicinity. The groundwater may be from precipitation or from groundwater flowing into the aquifer, in areas with sufficient precipitation, water infiltrates through pore spaces in the soil, passing through the unsaturated zone. At increasing depths water fills in more of the spaces in the soils. Below the water table, in the zone, layers of permeable rock that yield groundwater are called aquifers. In less permeable soils, such as tight bedrock formations and historic lakebed deposits, the water table should not be confused with the water level in a deeper well. The elevation of the water in this well is dependent upon the pressure in the deeper aquifer and is referred to as the potentiometric surface. The water table may vary due to changes such as precipitation and evapotranspiration. Springs, rivers, lakes and oases occur when the table reaches the surface. Springs commonly form on hillsides, where the Earths slanting surface may intersect with the water table, Groundwater entering rivers and lakes accounts for the base-flow water levels in water bodies. Within an aquifer, the table is rarely horizontal, but reflects the surface relief due to the capillary effect in soils, sediments. In the aquifer, groundwater flows from points of pressure to points of lower pressure. The slope of the table is known as the hydraulic gradient, which depends on the rate at which water is added to and removed from the aquifer. This occurs when there is a layer of rock or sediment or relatively impermeable layer above the main water table/aquifer. If a perched aquifers flow intersects the Earths dry surface, at a wall for example. On low-lying oceanic islands with porous soil, freshwater tends to collect in lenticular pools on top of the denser seawater intruding from the sides of the islands, such an islands freshwater lens, and thus the water table, rises and falls with the tides. In some regions, for example, Great Britain or California, winter precipitation is higher than summer precipitation
4.
Beach
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A beach is a landform along a body of water. It usually consists of particles, which are often composed of rock, such as sand, gravel, shingle, pebbles. The particles comprising a beach are occasionally biological in origin, such as shells or coralline algae. Some beaches have man-made infrastructure, such as posts, changing rooms. They may also have hospitality venues nearby, wild beaches, also known as undeveloped or undiscovered beaches, are not developed in this manner. Wild beaches can be valued for their beauty and preserved nature. Beaches typically occur in areas along the coast where wave or current action deposits, although the seashore is most commonly associated with the word beach, beaches are also found by lakes and alongside large rivers. Beach may refer to, small systems where rock material moves onshore, offshore, or alongshore by the forces of waves and currents, the former are described in detail below, the larger geological units are discussed elsewhere under bars. There are several parts to a beach that relate to the processes that form. The part mostly above water, and more or less influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline, the berm has a crest and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, at some point the influence of the waves on the material comprising the beach stops, and if the particles are small enough, winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune and these geomorphic features compose what is called the beach profile. The beach profile changes seasonally due to the change in energy experienced during summer and winter months. In temperate areas where summer is characterised by calmer seas and longer periods between breaking wave crests, the profile is higher in summer. The gentle wave action during this season tends to transport sediment up the beach towards the berm where it is deposited, onshore winds carry it further inland forming and enhancing dunes. Conversely, the profile is lower in the storm season due to the increased wave energy. The removal of sediment from the berm and dune thus decreases the beach profile
5.
Gully
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A gully is a landform created by running water, eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width, when the gully formation is in process, the water flow rate can be substantial, causing a significant deep cutting action into soil. The earliest known usage of the term is from 1657 and it originates from the French word goulet, a diminutive form of goule which means throat. It is possible that the term was derived from a type of knife at the time, gullying or gully erosion is the process by which gullies are formed. Hillsides are more prone to gullying when they are cleared of vegetation, through deforestation, the eroded soil is easily carried by the flowing water after being dislodged from the ground, normally when rainfall falls during short, intense storms such as during thunderstorms. A gully may grow in length by means of erosion at a knick point. This erosion can result from interflow as well as surface runoff, gullies reduce the productivity of farmland where they incise into the land, and produce sediment that may clog downstream waterbodies. Because of this, much effort is invested into the study of gullies within the scope of geomorphology, in the prevention of gully erosion, the total soil loss from gully formation and subsequent downstream river sedimentation can be sizeable. Gullies can be formed or enlarged by a number of human activities, artificial gullies are formed during hydraulic mining when jets or streams of water are projected onto soft alluvial deposits to extract gold or tin ore. The remains of mining methods are very visible landform features in old goldfields such as in California. The badlands at Las Medulas for example, were created during the Roman period by hushing or hydraulic mining of the gold-rich alluvium with water supplied by numerous aqueducts tapping nearby rivers, each aqueduct produced large gullies below by erosion of the soft deposits. The effluvium was carefully washed with smaller streams of water to extract the nuggets, gullies are widespread at mid- to high latitudes on the surface of Mars, and are some of the youngest features observed on that planet, probably forming within the last few 100,000 years. Flow as springs from deeper seated liquid water aquifers in the subsurface is also a possible explanation for the formation of some Martian gullies. Arroyo Coulee Couloir Canyon Gulch Ravine Wadi Lavaka Badlands Rill Oxford English Dictionary
6.
Lavaka
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Lavaka, the Malagasy word for hole, usually found on the side of a hill, is a type of erosional feature common in Madagascar. Lavakas form where these hard laterites overlie thick saprolite, on slopes, in areas that have a hot dry season. They are a type of gully, formed via groundwater sapping and they are usually shaped like a tear-drop with a steep, round headwall that narrows downhill into a shallow outlet channel. Although human activities—such as deforestation, overgrazing, road creation, and grassland burning—can contribute to lavaka formation, among the natural controls on lavaka formation are the amount of seismic activity in the region, the topographic relief, and hydraulic conductivity of materials in the saprolite. For instance, earthquakes in the region can cause cracks in the hard, upper layer of laterite, lavakas can often cause a lot of damage to nearby communities. During the monsoon season, heavy rains carry away all the material from the lavaka. This is the basis for much of the recent research that has conducted on the variables involved in lavaka formation. The term lavaka entered the international geography / geology vocabulary following the work of Riquier, cox, R. Bierman, P. Jungers, M. C. and Rakotondrazafy, A. F. M. 2009, Erosion rates and sediment sources in Madagascar inferred from 10Be analysis of lavaka, slope, Journal of Geology, v.117, p. 363-376. 2010, Shakedown in Madagascar, Occurrence of lavakas associated with seismic activity,2012, Relation Between Bedrock Geology, Topography and Lavaka Distribution in Madagascar. South African Journal of Geology 115.2, 225-250, raveloson, A. Visnovitz, F. Székely, B. 2012, A multidisciplinary study on lavaka formation in Central Highlands, raveloson, A. Visnovitz, F. Szabó, Cs. 2012, Sedimentological features of lateritic and saprolitic horizons in a mid-slope lavaka, Central Highlands, european Geoscience Union General Assembly April 22-27, Geophysical Research Abstracts, v.14, EGU2012-4365 Voarintsoa, N. R. Cox, R. Madison, R. M. O, Rakotondrazafy,2012, Lithologic controls on lavaka occurrence in Madagascar. South African Journal of Geology, v.115, p. 225-250,1991, Patterns of development of lavaka, Madagascars unusual gullies, Earth Surface Processes and Landforms, v.16, p. 189-206. 1993, The initiation and growth of gullies in Madagascar, are humans to blame, more about lavakas Lavaka image database at Williams College Digital Collections, Team Lavaka image collection
7.
U-shaped valley
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A glacier is a persistent body of dense ice that is constantly moving under its own weight, it forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs and they also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice, between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earths land surface, continental glaciers cover nearly 13,000,000 km2 or about 98 percent of Antarcticas 13,200,000 km2, with an average thickness of 2,100 m. Greenland and Patagonia also have huge expanses of continental glaciers, Glacial ice is the largest reservoir of fresh water on Earth. Within high altitude and Antarctic environments, the temperature difference is often not sufficient to release meltwater. A large piece of compressed ice, or a glacier, appears blue as large quantities of water appear blue and this is because water molecules absorb other colors more efficiently than blue. The other reason for the color of glaciers is the lack of air bubbles. Air bubbles, which give a color to ice, are squeezed out by pressure increasing the density of the created ice. The word Glaceon is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, the processes and features caused by or related to glaciers are referred to as glacial. The process of establishment, growth and flow is called glaciation. The corresponding area of study is called glaciology, Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, and behavior, cirque glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier, a large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have a less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called ice sheets or continental glaciers, several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces, the only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of water, enough that if both melted, global sea levels would rise by over 70 m
8.
Valley network
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Valley networks are branching networks of valleys on Mars that superficially resemble terrestrial river drainage basins. They are found mainly incised into the terrain of the southern highlands. The individual valleys are less than 5 kilometers wide, though they may extend for up to hundreds or even thousands of kilometers across the martian surface. Some authors have argued that the properties of the demand that a hydrological cycle must have been active on ancient Mars. The valleys of the networks are typically narrow and 50–200 m deep and their cross-sectional form tends to evolve from V-shaped in the headwaters to U-shaped in the lower reaches. The individual valleys form interconnected branching networks, typically less than 200 km long and draining into local topographic lows, the form of the tributary valleys is commonly described as stubby or a similar term, implying short lengths away from the trunk streams and amphitheater-like terminations at their heads. Any branched valley system on a smaller than an outflow channel can be termed a valley network. Some valley networks run for over 2000 km across the martian landscape, some have drainage densities which do match some terrestrial values. Narrower, less deep valley networks are present, but probably are more rare than their larger equivalents, in most valley networks, later aeolian processes have deposited wind-blown sediments in the bottoms of the valleys, obscuring the nature of the channel which must have cut them. On Earth, a valley is a depression with a floor, across which migrates a channel. Due to the deposits on Mars, however, in almost all cases it is unclear whether the valley floors contain individual channel structures or whether they are fully inundated in flow events. Nanedi Valles is an example where a channel has been identified. This accounts for the preference in the literature for the term valley network rather than channel network, valley networks are very strongly concentrated in the cratered southern uplands of Mars. The Hesperian-age lava plains of the northern hemisphere are in general almost entirely undissected, however, there are significant numbers of exceptions to this generalization - in particular, many of the Hesperian and younger volcanoes carry networks, as well as several other areas. These valleys also appear qualitatively fresher and less degraded than those in the highlands, however, at finer scales than this the distribution of the valleys where present is highly patchy and discontinuous. Within the highlands, it is not unusual to find heavily dissected slopes immediately adjacent to almost entirely unmodified surfaces and they are also much more prominent on steeper slopes, for example on crater rims, but again may only be present on one side of such a rim. However, the channels on Hesperian surfaces unambiguously demonstrate that valley-forming processes did continue at least in some locations at least some of the time after the Noachian, some crater counting evidence even suggests some highland networks may have formed in the Amazonian. Mechanisms and implied environments for the formation of the valleys remain contentious, beyond this, there are several different scenarios that have been advanced to account for the form and distribution in both space and time of the valleys
9.
Noachis Terra
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Noachis Terra is an extensive southern landmass of the planet Mars. It lies west of the giant Hellas impact basin, roughly between the latitudes −20° and −80° and longitudes 30° west and 30° east, centered on 45°S 350°E and it is in the Noachis quadrangle. The term Noachian epoch is derived from this region, the Planetary Report,34,1, 8-14 Lorenz, R. J. Zimbelman. Dune Worlds, How Windblown Sand Shapes Planetary Landscapes, springer Praxis Books / Geophysical Sciences. ESA Science and Technology, Noachis Terra
