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Spheroidal Weathering
Spheroidal weathering is a form of chemical weathering that affects jointed bedrock and results in the formation of concentric or spherical layers of highly decayed rock within weathered bedrock that is known as ''saprolite.'' When saprolite is exposed by physical erosion, these concentric layers peel (spall) off as concentric shells much like the layers of a peeled onion. Within saprolite, spheroidal weathering often creates rounded boulders, known as ''corestones'' or ''woolsack'', of relatively unweathered rock. Spheroidal weathering is also called onion skin weathering, concentric weathering, spherical weathering, or woolsack weathering.Fairbridge, RW (1968) ''Spheroidal Weathering.'' in RW Fairbridge, ed., pp. 1041–1044, The Encyclopedia of Geomorphology, Encyclopedia of Earth Sciences, vol. III. Reinhold Book Corporation, New York, New York. Ollier, C.D. (1971). ''Causes of spheroidal weathering. ''Earth-Science Reviews 7:127–141.Neuendorf, KKE, JP Mehl Jr., and JA J ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haytor Evening Light
Haytor, also known as Haytor Rocks, Hay Tor, or occasionally Hey Tor, is a granite tor on the eastern edge of Dartmoor in the English county of Devon. Location The tor is at grid reference , near the village of Haytor Vale in the parish of Ilsington. There is an electoral ward with the same name. The population at the 2011 census is 2,862. History ''Idetordoune'' (1566), ''Ittor Doune'' (1687), ''Idetor'' (1737), ''Eator Down'' (1762) and ''Itterdown'' (1789) are a few recorded examples of earlier names by which Haytor was known. The name ''Haytor'' is of comparatively recent origin, and is probably a corruption of its old name and that of the Haytor Hundred, which covered the coastal area between the River Teign and River Dart, itself now considered to have been named after a lost village located somewhere between Totnes and Newton Abbot. In the 19th century steps were made to allow pedestrians up to the top of the tor and a metal handrail fixed to allow tourists easier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sericite
Sericite is the name given to very fine, ragged grains and aggregates of white (colourless) micas, typically made of muscovite, illite, or paragonite. Sericite is produced by the alteration of orthoclase or plagioclase feldspars in areas that have been subjected to hydrothermal alteration typically associated with copper, tin, or other hydrothermal ore deposits. Sericite also occurs as the fine mica that gives the sheen to phyllite and schistose metamorphic rocks. The name comes from Latin ''sericus'', meaning "silken" in reference to the location from which silk was first utilized, which in turn refers to the silky sheen of rocks with abundant sericite. File:Granite pmg ss 2006.jpg, Granite in thin section under cross-polarized light in which feldspar crystals exhibit sericite alteration. File:Staurolite garnet schist 3mm xp 2007.jpg, Staurolite-garnet schist in thin section under cross-polarized light with sericite. References External linksMindat [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Processes
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth sciences, including hydrology, and so is treated as one major aspect of integrated Earth system science and planetary science. Geology describes the structure of the Earth on and beneath its surface, and the processes that have shaped that structure. It also provides tools to determine the relative and absolute ages of rocks found in a given location, and also to describe the histories of those rocks. By combining these tools, geologists are able to chronicle the geological history of the Earth as a whole, and also to demonstrate the age of the Earth. Geology provides the primary evidence for plate tectonics, the evolutionary history of life, and the Earth's past climates. Geologists broadly study the properties and processes of Ear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weathering Rind
A weathering rind is a discolored, chemically altered, outer zone or layer of a discrete rock fragment formed by the processes of weathering. The inner boundary of a weathering rind approximately parallels the outer surface of the rock fragment in which it has developed. Rock fragments with weathering rinds normally are discrete clasts, ranging in size from pebbles to cobbles or boulders. They typically occur either lying on the surface of the ground or buried within sediments such as alluvium, colluvium, or glacial till. A weathering rind represents the alteration of the outer portion of a rock by exposure to air or near surface groundwater over a period of time. Typically, a weathering rind may be enriched with either iron or manganese (or both), and silica, and oxidized to a yellowish red to reddish color. Often a weathering rind exhibits multiple bands of differing colors.Colman, SM, and KL Pierce (2001) ''Weathering rinds on andesitic and basaltic stones as a Quaternary a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exfoliating Granite
Exfoliating granite is a granite undergoing exfoliation, or onion skin weathering (desquamation). The external delaminated layers of granite are gradually produced by the cyclic variations of temperature at the surface of the rock in a process also called spalling. Frost and ice expansion in the joints during the winter accelerate the alteration process while the most unstable loosen external layers are removed by gravity assisted by runoff water. Geology Homogeneous granitic plutons are created in high-pressure environments and slowly solidify beneath the earth's crust. Vertical compression of overburden releases through erosion, or removal of overlying rocks resulting in unloading.Petersen, James F., Dorthy Sack, and Robert E. Gabler. "Pg. 292." Fundamentals of Physical Geography. 1st ed. Belmont: Brooks/Cole, 2010. 292-93. Print.Lutgens, Frederick K., and Edward J. Tarbuck. "Entire Book." Essentials Of Geology. 9th ed. Upper Saddle River: Pearson Prentice Hall, 2006. 118- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exfoliation (geology)
Exfoliation joints or sheet joints are surface-parallel fracture systems in rock, and often leading to erosion of concentric slabs. ''(See Joint (geology)).'' General characteristics of exfoliation joints * Commonly follow topography. * Divide the rock into sub-planar slabs. * Joint spacing increases with depth from a few centimeters near the surface to a few meters * Maximum depth of observed occurrence is around 100 meters. * Deeper joints have a larger radius of curvature, which tends to round the corners of the landscape as material is eroded * Fracture mode is tensile * Occur in many different lithologies and climate zones, not unique to glaciated landscapes. * Host rock is generally sparsely jointed, fairly isotropic, and has high compressive strength. * Can have concave and convex upwards curvatures. * Often associated with secondary compressive forms such as arching, buckling, and A-tents (buckled slabs) Formation of exfoliation joints Despite their common occu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liesegang Rings (geology)
Liesegang rings () (also called Liesegangen rings or Liesegang bands) are colored bands of cement observed in sedimentary rocks that typically cut across bedding.Stow, A.V., 2009, Sedimentary rocks in the field. A color guide (3rd ed.), Pp. 103, 107. These secondary ( diagenetic) sedimentary structures exhibit bands of (authigenic) minerals that are arranged in a regular repeating pattern.Middleton, Gerard V.; Church, Michael J.; Coniglio, Mario; Hardie, Lawrence A.; Longstaffe, Frederick J.; 2003. "Encyclopedia of Sediments and Sedimentary Rocks." Kluwer Academic Publishers, Dordrecht. Pp. 221, 224. Liesegang rings are distinguishable from other sedimentary structures by their concentric or ''ring-like'' appearance. The precise mechanism from which Liesegang rings form is not entirely known and is still under research,Krug, H.-J,. Brandtstadter, H., and Jacob, K.H., 1996. Morphological instabilities in pattern formation by precipitation and crystallization processes. ''Geolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piotr Migoń
Piotr Migoń is a Polish geomorphologist active at the university of Wrocław where he hold a chair as Professor of Geography. Migoń has specialized in the study of weathering, mass movements in mountains, long-term landscape evolution and the geomorphology of granite and sandstone areas. Most of his research has been carried out in the Sudetes and other parts of Central Europe Central Europe is an area of Europe between Western Europe and Eastern Europe, based on a common historical, social and cultural identity. The Thirty Years' War (1618–1648) between Catholicism and Protestantism significantly shaped the a .... He is currently an International Association of Geomorphologists board member. References Year of birth missing (living people) Living people Polish geomorphologists Academic staff of the University of Wrocław {{Poland-scientist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Rowland Twidale
Charles Rowland Twidale is an Australian geomorphologist active at the University of Adelaide. Twidale's research has covered varied subjects including structural geomorphology, weathering, ancient landscapes in shield regions, granite landforms in deserts, paleosurfaces and the history of geomorphology. Twidale has been most active investigating the geomorphology of Australia and Spain. In 1976 C. R. Twidale was president of the Royal Society of South Australia. In 1993 he was awarded the Mueller Medal The Australian and New Zealand Association for the Advancement of Science (ANZAAS) is an organisation that was founded in 1888 as the Australasian Association for the Advancement of Science to promote science. It was modelled on the British As ... by the Australian and New Zealand Association for the Advancement of Science.ANZAAS > Mueller Medal Recipientsarchive.is Retrieved 9 July 2017, References External links * Australian geomorphologists Historians of scie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tor (rock Formation)
A tor, which is also known by geomorphologists as either a castle koppie or kopje, is a large, free-standing rock outcrop that rises abruptly from the surrounding smooth and gentle slopes of a rounded hill summit or ridge crest. In the South West of England, the term is commonly also used for the hills themselves – particularly the high points of Dartmoor in Devon and Bodmin Moor in Cornwall.Ehlen, J. (2004) ''Tor'' in Goudie, A., ed., pp. 1054-1056. ''Encyclopedia of Geomorphology.'' Routledge. London, England. Etymology Although English topographical names often have a Celtic etymology, the Oxford English Dictionary lists no cognates to the Old English word in either the Breton or Cornish languages (the Scottish Gaelic ''tòrr'' is thought to derive from the Old English word). It is therefore accepted that the English word ''Tor'' derives from the Old Welsh word ''tẁrr'' or ''twr'', meaning a cluster or heap. Formation Tors are landforms created by the erosion and w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as ''physical'' or ''mechanical'' erosion; this contrasts with ''chemical'' erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Agents of erosion include rainfall; bedrock wear in rivers; coastal erosion by the sea and waves; glacial plucking, abrasion, and scour; areal flooding; wind abrasion; groundwater processes; and mass movement processes in steep landscapes like landslides and debris flows. The rates at which such processes act control how fast a surface is eroded. Typically, physical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorite
The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous acid. Compounds The free acid, chlorous acid HClO2, is the least stable oxoacid of chlorine and has only been observed as an aqueous solution at low concentrations. Since it cannot be concentrated, it is not a commercial product. The alkali metal and alkaline earth metal compounds are all colorless or pale yellow, with sodium chlorite (NaClO2) being the only commercially important chlorite. Heavy metal chlorites (Ag+, Hg+, Tl+, Pb2+, and also Cu2+ and ) are unstable and decompose explosively with heat or shock. Sodium chlorite is derived indirectly from sodium chlorate, NaClO3. First, the explosively unstable gas chlorine dioxide, ClO2 is produced by reducing sodium chlorate with a suitable reducing agent such as methanol, hydrogen per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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