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Sinkholes
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openings where surface water enters into underground passages known as '' ponor'', swallow hole or swallet. A ''cenote'' is a type of sinkhole that exposes groundwater underneath. A ''sink'' or ''stream sink'' are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock. Most sinkholes are caused by karst processes – the chemical dissolution of carbonate rocks, collapse or suffosion processes. Sinkholes are usually circular and vary in size from tens to hundreds of meters both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide. Formation Natural processes Sinkholes may capture su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karst Topography
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant rocks, such as quartzite, given the right conditions. Subterranean drainage may limit surface water, with few to no rivers or lakes. However, in regions where the dissolved bedrock is covered (perhaps by debris) or confined by one or more superimposed non-soluble rock strata, distinctive karst features may occur only at subsurface levels and can be totally missing above ground. The study of ''paleokarst'' (buried karst in the stratigraphic column) is important in petroleum geology because as much as 50% of the world's hydrocarbon reserves are hosted in carbonate rock, and much of this is found in porous karst systems. Etymology The English word ''karst'' was borrowed from German in the late 19th century, which entered German much ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cedar Sink
Cedar Sink is a vertical-walled large depression, or sinkhole, in the ground, that is located in Edmonson County, Kentucky Edmonson County is a county located in the south central portion of the U.S. state of Kentucky. As of the 2020 census, the population was 12,126. Its county seat is Brownsville. The county was formed in 1825 and named for Captain John "Jack" E ... and contained within and managed by Mammoth Cave National Park. The sinkhole measures from the top sandstone plateau to the bottom of the sink and was caused by collapse of the surface soil. The landscape is karst topography, which means the region is influenced by the dissolution of soluble rocks. Sinkholes, caves, and Sinkhole, dolines typically characterize these underground drainage systems. Cedar Sink has a bottom area of about and has more fertile soil compared to the ridgetops. Geomorphology Rock age The rocks of Cedar Sink and the surrounding area are from the Mississippian (geology), Mississippian (al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suffosion
Suffosion is one of the two geological processes by which subsidence sinkholes or dolines are formed, the other being due to collapse of an underlying cave or void, with most sinkholes formed by the suffosion process. Suffosion sinkholes are normally associated with karst topography although they may form in other types of rock including chalk, gypsum and basalt. In the karst of the UK's Yorkshire Dales, numerous surface depressions known locally as "shakeholes" are the result of glacial till washing into fissures in the underlying limestone. Process Suffosion occurs when loose soil, loess, or other non-cohesive material lies on top of a limestone substratum containing fissures and joints. Rain and surface water gradually wash this material through these fissures and into caves beneath. Over time, this creates a depression on the landscape of varying depth. Suffosion versus suffusion Suffosion is a destructive process that creates instability leading to collapse of the soil struct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rosetta (spacecraft)
''Rosetta'' was a space probe built by the European Space Agency launched on 2 March 2004. Along with ''Philae (spacecraft), Philae'', its lander module, ''Rosetta'' performed a detailed study of comet 67P/Churyumov–Gerasimenko (67P). During its journey to the comet, the spacecraft performed planetary flyby, flybys of Earth, Mars, and the asteroids 21 Lutetia and 2867 Šteins. It was launched as the third cornerstone mission of the ESA's Horizon 2000 programme, after ''Solar and Heliospheric Observatory, SOHO'Cluster II (spacecraft), Cluster'' and ''XMM-Newton''. On 6 August 2014, the spacecraft reached the comet and performed a series of manoeuvers to eventually orbit the comet at distances of . On 12 November, its lander module ''Philae'' performed the first successful landing on a comet, though its battery power ran out two days later. Communications with ''Philae'' were briefly restored in June and July 2015, but due to diminishing solar power, ''Rosetta'' communications ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cenote
A cenote ( or ; ) is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater. The regional term is specifically associated with the Yucatán Peninsula of Mexico, where cenotes were commonly used for water supplies by the ancient Maya, and occasionally for sacrificial offerings. The term derives from a word used by the lowland Yucatec Maya——to refer to any location with accessible groundwater. Similar rock-sided sinkholes like cenotes are common geological forms in low-altitude regions, particularly on islands, coastlines, and platforms with young post-Paleozoic limestone with little soil development. The term ''cenote'' has also been used to describe similar karst features in other countries such as Cuba and Australia. Definition and description Cenotes are surface connections to subterranean water bodies. While the best-known cenotes are large open-water pools measuring tens of meters in diameter, such as those at Chichen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or Coma (cometary), coma, and sometimes also a Comet tail, tail. These phenomena are due to the effects of solar radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times Earth's diameter, while the tail may stretch beyond one astronomical unit. If sufficiently bright, a comet may be seen from Earth without the aid of a telescope and may Subtended angle, subtend an arc of 30° (60 Moons) across the sky. Comets have been observed and recorded since ancient times by many cultures and religions. Comets usually have highly Orbital eccentricity, eccentric elliptical orbits, and they have a wide range of orbit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cavern
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea caves, rock shelters, and grottos, that extend a relatively short distance into the rock and they are called ''exogene'' caves. 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'', ''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, microorgani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country in Oceania that comprises the eastern half of the island of New Guinea and its offshore islands in Melanesia (a region of the southwestern Pacific Ocean north of Australia). Its capital, located along its southeastern coast, is Port Moresby. The country is the world's third largest island country, with an area of . At the national level, after being ruled by three external powers since 1884, including nearly 60 years of Australian administration starting during World War I, Papua New Guinea established its sovereignty in 1975. It became an independent Commonwealth realm in 1975 with Elizabeth II as its queen. It also became a member of the Commonwealth of Nations in its own right. There are 839 known languages of Papua New Guinea, on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ground Water
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology. Typically, groundwater is thought of as water flowing through shallow aquifers, but, in the technical sense, it can also contain soil moisture, permafr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. Alabaster, a fine-grained white or lightly tinted variety of gypsum, has been used for sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England. Gypsum also crystallizes as translucent crystals of selenite. It forms as an evaporite mineral and as a hydration product of anhydrite. The Mohs scale of mineral hardness defines gypsum as hardness value 2 based on scratch hardness comparison. Etymology and history The word '' gypsum'' is derived from the Greek word (), "plaster". Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum ( calcined gypsum) used for various purposes, this dehydrated gyp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halite
Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on inclusion of other materials, impurities, and structural or isotopic abnormalities in the crystals. It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides, and borates. The name ''halite'' is derived from the Ancient Greek word for "salt", ἅλς (''háls''). Occurrence Halite dominantly occurs within sedimentary rocks where it has formed from the evaporation of seawater or salty lake water. Vast beds of sedimentary evaporite minerals, including halite, can result from the drying up of enclosed lakes and restricted seas. Such salt beds may be hundreds of meters thick and underlie broad areas. Halite occurs at the surface today in playas in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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