|
Médanos (geology)
__NOTOC__ In South America, the word médanos refers to continental dunes whereas dunas refers to dunes of coastal origin. Médanos may be vegetated or unvegetated. For example, the médanos of La Pampa Province in Argentina are mostly vegetated dunes with occasional blowouts. On the other hand, the dunes of Médanos de Coro National Park in Venezuela are mostly unvegetated. An early description of unvegetated médanos in Peru is provided by the Swiss naturalist and explorer Johann Jakob von Tschudi (1847):Tschudi, J.J. von. 1847. Travels in Peru during the years 1838-1842. New York: Wiley & Putnam, 354 pp. (Translated from the German by Thomasina Ross) "The médanos are hillock-like elevations of sand, some having a firm, others a loose base. The former, which are always crescent-shaped, are from ten to twenty feet high, and have an acute crest. The inner side is perpendicular, and the outer or bow side forms an angle with a steep inclination downward. When driven by vio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dune
A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat regions covered with wind-swept sand or dunes with little or no vegetation are called ''ergs'' or ''sand seas''. Dunes occur in different shapes and sizes, but most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter ''slip face'' in the lee side. The valley or trough between dunes is called a ''dune slack''. Dunes are most common in desert environments, where the lack of moisture hinders the growth of vegetation that would otherwise interfere with the development of dunes. However, sand deposits are not restricted to deserts, and dunes are also found along sea shores, along streams in semiarid climates, in areas of glacial outwash, and in other areas where poorly cemented sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
La Pampa Province
La Pampa () is a sparsely populated province of Argentina, located in the Pampas in the center of the country. Neighboring provinces are from the north clockwise San Luis, Córdoba, Buenos Aires, Río Negro, Neuquén and Mendoza. History In 1604 Hernando Arias de Saavedra was the first European explorer to reach the area; it was later explored by Jerónimo Luis de Cabrera in 1662. But it was not until the 18th century that Spanish colonists established permanent settlements here. Resistance of the local indigenous people prevented much expansion until the government of Juan Manuel de Rosas. It did not cease until Julio Roca's conquest of the desert in the 19th century. The territory was divided between the officers, and they erected the first Argentine settlements. The ''Territorio Nacional de La Pampa Central'' was erected in 1884, containing the Río Negro Province and parts of other surrounding provinces. It had around 25,000 inhabitants. By 1915 there were 110,000 resid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, the fourth-largest country in the Americas, and the eighth-largest country in the world. It shares the bulk of the Southern Cone with Chile to the west, and is also bordered by Bolivia and Paraguay to the north, Brazil to the northeast, Uruguay and the South Atlantic Ocean to the east, and the Drake Passage to the south. Argentina is a federal state subdivided into twenty-three provinces, and one autonomous city, which is the federal capital and largest city of the nation, Buenos Aires. The provinces and the capital have their own constitutions, but exist under a federal system. Argentina claims sovereignty over the Falkland Islands, South Georgia and the South Sandwich Islands, and a part of Antarctica. The earliest recorded human prese ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blowout (geomorphology)
Blowouts are sandy depressions in a sand dune ecosystem (psammosere) caused by the removal of sediments by wind. Commonly found in coastal settings and margins of arid areas, blowouts tend to form when wind erodes patches of bare sand on stabilized vegetated dunes. Generally, blowouts do not form on actively flowing dunes due to the fact that the dunes need to be bound to some extent, for instance by plant roots. These depressions usually start on the higher parts of stabilized dunes on account of the more considerable desiccation and disturbances occurring there, which allows for greater surface drag and sediment entrainment when the sand is bare. Most of the time, exposed areas become quickly re-vegetated before they can become blowouts and expand; however, when circumstances are favourable, wind erosion can gouge the exposed surface and create a tunneling effect which increases local wind speed. A depression may then develop until it hits a non-erodible substrate, or morphol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Médanos De Coro National Park
Médanos de Coro National Park (''Parque Nacional Los Médanos de Coro'') is a Venezuelan national park located in the state of Falcón State, Falcón, near the city of Santa Ana de Coro, Coro on the road that leads to Paraguaná. The National Park was created in 1974. The park is easily reached by bus or taxi from Coro. The Médanos park protects part of the Paraguana xeric scrub ecoregion. It lies on the Médanos Isthmus and covers of desert and coastal habitat, including salt marshes. It is made up of three zones: an alluvial plain, formed by the delta of the Mitare River and some smaller streams; an aeolian plain, composed of three types of dunes; and a littoral plain with a belt of mangrove swamps. The massive sand dunes, known as Médanos, spread over an area of approximately . They can reach in height and are constantly transformed by the unrelenting wind. Rainfall is rare. However, during the severe floods that struck Venezuela in December 1999 ("Vargas tragedy", being ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johann Jakob Von Tschudi
Johann Jakob von Tschudi (25 July 1818 – 8 October 1889) was a Switzerland, Swiss Natural history, naturalist, explorer and diplomat. Biography Tschudi was born in Glarus to Johann Jakob Tschudi, a merchant, and Anna Maria Zwicky. He studied natural sciences and medicine at the universities of Neuchâtel, Leiden and Paris. In 1838 he travelled to Peru, where he remained for five years exploring and collecting plants in the Andes. He went to Vienna in 1843. In 1845 he described 18 new species of South American reptiles. Between 1857 and 1859 he visited Brazil and other countries in South America. In 1860 he was appointed Swiss ambassador to Brazil, remaining so until 1868, and again spent time exploring the country and collecting plants for the museums of Neuchâtel, Glarus, and Freiburg. In 1868 he became minister to Vienna. Peru He wrote a textbook on Peru called ''Peruvian antiquities'' in which he recorded various aspects of Peruvian life and history. In his book he explai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aeolian Processes
Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and deposit materials and are effective agents in regions with sparse vegetation, a lack of soil moisture and a large supply of unconsolidated sediments. Although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as deserts. The term is derived from the name of the Greek god Aeolus, the keeper of the winds. Definition and setting ''Aeolian processes'' are those processes of erosion, transport, and deposition of sediments that are caused by wind at or near the surface of the earth. Sediment deposits produced by the action of wind and the sedimentary structures characteristic of these deposits are also described as ''aeolian''. Aeolian processes are most important in areas where there is little or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barchan
A barchan or barkhan dune (from Kazakh бархан ) is a crescent-shaped dune. The term was introduced in 1881 by Russian naturalist Alexander von Middendorf, based on their occurrence in Turkestan and other inland desert regions. Barchans face the wind, appearing convex and are produced by wind action predominantly from one direction. They are a very common landform in sandy deserts all over the world and are arc-shaped, markedly asymmetrical in cross section, with a gentle slope facing toward the wind sand ridge, comprising well-sorted sand. This type of dune possesses two "horns" that face downwind, with the steeper slope known as the slip face, facing away from the wind, downwind, at the angle of repose of the sand in question, approximately 30–35 degrees for medium-fine dry sand. The upwind side is packed by the wind, and stands at about 15 degrees. Barchans may be high and wide at the base measured perpendicular to the wind. Simple barchan dunes may appear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blowout (geology)
Blowouts are sandy depressions in a sand dune ecosystem (psammosere) caused by the removal of sediments by wind. Commonly found in coastal settings and margins of arid areas, blowouts tend to form when wind erodes patches of bare sand on stabilized vegetated dunes. Generally, blowouts do not form on actively flowing dunes due to the fact that the dunes need to be bound to some extent, for instance by plant roots. These depressions usually start on the higher parts of stabilized dunes on account of the more considerable desiccation and disturbances occurring there, which allows for greater surface drag and sediment entrainment when the sand is bare. Most of the time, exposed areas become quickly re-vegetated before they can become blowouts and expand; however, when circumstances are favourable, wind erosion can gouge the exposed surface and create a tunneling effect which increases local wind speed. A depression may then develop until it hits a non-erodible substrate, or morphol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jean Tricart
Jean Tricart (16 September 1920 – 6 May 2003) was a French geomorphologist. In 1948 he became professor at the University of Strasbourg where he remained for the rest of his career. The Tricart's doctoral thesis dealt with the Paris Basin The Paris Basin is one of the major geological regions of France. It developed since the Triassic over remnant uplands of the Variscan orogeny (Hercynian orogeny). The sedimentary basin, no longer a single drainage basin, is a large sag in th ... and resulted in a publication acclaimed in France. He collaborated often with his friend André Cailleux. Beginning in 1962 he and Callieux published a band of five works on the subject of geomorphology and climate, publishing the last one in 1974. The bulk of his works were published in French. Tricart considered that he had, 'a broad systems approach to landform genesis.'. This paper is response to Denys Brunsden's 'Tablets of Stone'.Brunsden, D. 1990. Tablets of stone: toward the Ten Command ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
