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River Valley
A valley is an elongated low area often running between hills or mountains and typically containing a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a very long period. Some valleys are formed through erosion by glacial ice. These glaciers may remain present in valleys in high mountains or polar areas. At lower latitudes and altitudes, these glacially formed valleys may have been created or enlarged during ice ages but now are ice-free and occupied by streams or rivers. In desert areas, valleys may be entirely dry or carry a watercourse only rarely. In areas of limestone bedrock, dry valleys may also result from drainage now taking place underground rather than at the surface. Rift valleys arise principally from earth movements, rather than erosion. Many different types of valleys are described by geographers, using terms that may be global in use or else applied only locally. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cave
Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance underground (such as rock shelters). Caves which extend further underground than the opening is wide are called endogene caves. Speleology is the science of exploration and study of all aspects of caves and the cave environment. Visiting or exploring caves for recreation may be called Caving, ''caving'', ''potholing'', or ''spelunking''. Formation types The formation and development of caves is known as ''speleogenesis''; it can occur over the course of millions of years. Caves can range widely in size, and are formed by various geological processes. These may involve a combination of chemical processes, erosion by water, tectonic forces, microorganisms, pressure, and atmospheric influences. Isotopic dating techniques can be applied to cave sedime ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fold (geology)
In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary rock, sedimentary stratum, strata, that are bent or curved (''"folded"'') during permanent deformation (engineering), deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets (known as ''fold trains''). wikt:synsedimentary, Synsedimentary folds are those formed during sedimentary deposition. Folds form under varied conditions of stress (physics), stress, pore pressure, and temperature gradient, as evidenced by their presence in soft sedimentary rock, 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 orogeny, orogenic zones. Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fracture (geology)
A fracture is any separation in a geologic formation, such as a Joint (geology), ''joint'' or a Fault (geology), ''fault'' that divides the Rock (geology), rock into two or more pieces. A fracture will sometimes form a deep fissure or crevice in the rock. Fractures are commonly caused by Stress (physics), stress exceeding the rock strength, causing the rock to lose cohesion along its weakest plane. Fractures can provide Permeability (fluid), permeability for fluid movement, such as water or hydrocarbons. Highly fractured rocks can make good aquifers or Oil reservoir, hydrocarbon reservoirs, since they may possess both significant Permeability (fluid), permeability and fracture porosity. Brittle deformation Fractures are forms of brittle deformation. There are two types of primary brittle deformation processes. Tensile fracturing results in ''joints''. ''Shear fractures'' are the first initial breaks resulting from shear forces exceeding the cohesive strength in that plane. Aft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault (geology)
In geology, a fault is a Fracture (geology), planar fracture or discontinuity in a volume of Rock (geology), rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust (geology), crust result from the action of Plate tectonics, plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction, subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the Plane (geometry), plane that represents the fracture surface of a fault. A ''fault trace'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geological maps to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corrasion
Corrasion is a geomorphological Geomorphology () is the scientific study of the origin and evolution of topography, topographic and bathymetry, bathymetric features generated by physical, chemical or biological processes operating at or near Earth#Surface, Earth's surface. Ge ... term for the process of mechanical erosion of the earth's surface caused when materials are transported across it by running water, waves, glaciers, wind or gravitational movement downslope. An example is the wearing away of rock on a river or seabed by the impact or grinding action of particles moving with the water. The resultant effect on the rock is called abrasion. Corrasion is different from corrosion which is due to chemical and solvent action of water on soluble or partly soluble rocks when they come in contact. Corrasion acts in two ways: # Lateral corrasion : the sideways erosion which widens the river. # Vertical corrasion: downward erosion which deepens the river valley. Thus corrasi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Valley
A valley is an elongated low area often running between hills or mountains and typically containing a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a very long period. Some valleys are formed through erosion by glacial ice. These glaciers may remain present in valleys in high mountains or polar areas. At lower latitudes and altitudes, these glacially formed valleys may have been created or enlarged during ice ages but now are ice-free and occupied by streams or rivers. In desert areas, valleys may be entirely dry or carry a watercourse only rarely. In areas of limestone bedrock, dry valleys may also result from drainage now taking place underground rather than at the surface. Rift valleys arise principally from earth movements, rather than erosion. Many different types of valleys are described by geographers, using terms that may be global in use or else applied only locally. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluvial Terrace
Fluvial terraces are elongated Terrace (geology), terraces that flank the sides of floodplains and fluvial valleys all over the world. They consist of a relatively level strip of land, called a "tread", separated from either an adjacent floodplain, other fluvial terraces, or uplands by distinctly steeper strips of land called "risers". These terraces lie parallel to and above the river channel and its floodplain. Because of the manner in which they form, fluvial terraces are underlain by fluvial sediments of highly variable thickness. River terraces are the remnants of earlier floodplains that existed at a time when either a stream or river was flowing at a higher elevation before its channel downcut to create a new floodplain at a lower elevation. Changes in elevation can be due to changes in the base level (elevation of the lowest point in the fluvial system, usually the drainage basin) of the fluvial system, which leads to headward erosion along the length of either a stream or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rifting
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear Fault (geology), downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. ''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a Hotspot (geology), hotspot. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endorheic Basin
An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent and seasonal lakes and swamps that equilibrate through evaporation. Endorheic basins are also called closed basins, terminal basins, and internal drainage systems. Endorheic regions contrast with open lakes (exorheic regions), where surface waters eventually drain into the ocean. In general, water basins with subsurface outflows that lead to the ocean are not considered endorheic; but cryptorheic. Endorheic basins constitute local base levels, defining a limit of the erosion and deposition processes of nearby areas. Endorheic water bodies include the Caspian Sea, which is the world's largest inland body of water. Etymology The term ''endorheic'' derives from the French word , which combines ( 'within') and 'flow'. Endorheic lake ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
