|
Gypcrust
Gypcrete or gypcrust is a hardened layer of soil, consisting of around 95% gypsum (calcium sulfate). Gypcrust is an arid zone duricrust. It can also occur in a semiarid climate in a basin with internal drainage, and is initially developed in a playa as an evaporate. Gypcrete is the arid climate's equivalent to calcrete, which is a duricrust that is unable to generate in very arid climates. Composition Gypcrust horizons can be up to thick with a 75-97% gypsum (CaSO4∙2H2O) content. The majority of gypsum-rich layers occur where the average annual rainfall is less than 250 mm because gypsum is moderately soluble (c. 2.6 g−1 at 25 °C) and is normally leached out under higher rainfall conditions. Gypsum cements are rarely, if ever, as strong as calcretes or silcretes. Formation Gypcrust forms in a manner similar to that of caliche, which is composed of calcium carbonate. The development of gypcrust has 3 main stages. The first stage is primary crystallization ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duricrust
Duricrust is a hard layer on or near the surface of soil. Duricrusts can range in thickness from a few millimeters or centimeters to several meters. It is a general term (not to be confused with duripan) for a zone of chemical precipitation and hardening formed at or near the surface of sedimentary bodies through pedogenic and (or) non-pedogenic processes. It is typically formed by the accumulation of soluble minerals deposited by mineral-bearing waters that move upward, downward, or laterally by capillary action, commonly assisted in arid settings by evaporation.Dixon, J.C. and McLaren, S.J., 2009. ''Duricrusts''. In A.J. Parsons and A.D. Abrahams, ed., pp. 123-151. ''Geomorphology of desert environments.'' Springer, Dordrecht. Woolnough, W.G., 1930. ''The influence of climate and topography in the formation and distribution of products of weathering.'' ''Geological Magazine'', 67(3), pp.123-132. There are different types of duricrusts, each distinguished by a dominant mineralo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcrete
Caliche () is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, including in central and western Australia, in the Kalahari Desert, in the High Plains of the western United States, in the Sonoran Desert, Chihuahuan Desert and Mojave Desert of North America, and in eastern Saudi Arabia at Al-Hasa. Caliche is also known as calcrete or kankar (in India). It belongs to the duricrusts. The term ''caliche'' is Spanish and is originally from the Latin ''calx'', meaning lime. Caliche is generally light-colored, but can range from white to light pink to reddish-brown, depending on the impurities present. It generally occurs on or near the surface, but can be found in deeper subsoil deposits, as well. Layers vary from a few inches to feet thick, and multiple layers can exist in a single location. A caliche lay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caliche (mineral)
Caliche () is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, including in central and western Australia, in the Kalahari Desert, in the High Plains of the western United States, in the Sonoran Desert, Chihuahuan Desert and Mojave Desert of North America, and in eastern Saudi Arabia at Al-Hasa. Caliche is also known as calcrete or kankar (in India). It belongs to the duricrusts. The term ''caliche'' is Spanish and is originally from the Latin ''calx'', meaning lime. Caliche is generally light-colored, but can range from white to light pink to reddish-brown, depending on the impurities present. It generally occurs on or near the surface, but can be found in deeper subsoil deposits, as well. Layers vary from a few inches to feet thick, and multiple layers can exist in a single location. A caliche lay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former term specifically to displaced soil. Soil consists of a solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution). Accordingly, soil is a three-state system of solids, liquids, and gases. Soil is a product of several factors: the influence of climate, relief (elevation, orientation, and slope of terrain), organisms, and the soil's parent materials (original minerals) interacting over time. It continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion. Given its complexity and strong internal connectedness, soil ecologists regard soil as an ecosystem. Most ... [...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 gypsum became known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Sulfate
Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum. It has many uses in industry. All forms are white solids that are poorly soluble in water.Franz Wirsching "Calcium Sulfate" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH, Weinheim. Calcium sulfate causes permanent hardness in water. Hydration states and crystallographic structures The compound exists in three levels of hydration corresponding to different crystallographic structures and to minerals: * (anhydrite): anhydrous state. The structure is related to that of zirconium orthosilicate (zircon): is 8-coordinate, is tetrahedral, O is 3-coordinate. * (gypsum and selenite (mineral)): dihydrate. * (bassanite): hemihydrate, also known as plaster of Paris. S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capillary Fringe
The capillary fringe is the subsurface layer in which groundwater seeps up from a water table by capillary action to fill pores. Pores at the base of the capillary fringe are filled with water due to tension saturation. This saturated portion of the capillary fringe is less than total capillary rise because of the presence of a mix in pore size. If pore size is small and relatively uniform, it is possible that soils can be completely saturated with water for several feet above the water table. Alternately, when pore size is large, the saturated portion will extend only a few inches above the water table. Capillary action supports a vadose zone above the saturated base within which water content decreases with distance above the water table. In soils with a wide range in pore size, the unsaturated zone can be several times thicker than the saturated zone. Some workers restrict their definition of the capillary fringe only to the tension-saturated base portion and exclude it wholly f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sand Rose
A desert rose is an intricate rose-like formation of crystal clusters of gypsum or baryte, which include abundant sand grains. The "petals" are crystals flattened on the ''c'' axis, fanning open in radiating clusters. The rosette crystal habit tends to occur when the crystals form in arid sandy conditions, such as the evaporation of a shallow salt basin. The crystals form a circular array of flat plates, giving the rock a shape similar to a rose blossom. Gypsum roses usually have better defined, sharper edges than baryte roses. Celestine and other bladed evaporite minerals may also form rosette clusters. They can appear either as a single rose-like bloom or as clusters of blooms, typically ranging from pea-sized to in diameter. The ambient sand that is incorporated into the crystal structure, or otherwise encrusts the crystals, varies with the local environment. If iron oxides are present, the rosettes take on a rusty tone. The desert rose may also be known by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aggregate (geology)
In the Earth sciences, aggregate has three possible meanings. In mineralogy and petrology, an aggregate is a mass of mineral crystals, mineraloid particles or rock particles. Examples are dolomite, which is an aggregate of crystals of the mineral dolomite, and ''rock gypsum'', an aggregate of crystals of the mineral gypsum. Lapis lazuli is a type of rock composed of an aggregate of crystals of many minerals including lazurite, pyrite, phlogopite, calcite, potassium feldspar, wollastonite and some sodalite group minerals. In the construction industry, an aggregate (often referred to as a construction aggregate) is sand, gravel or crushed rock that has been mined or quarried for use as a building material. In pedology, an aggregate is a mass of soil particles. If the aggregate has formed naturally, it can be called a ped; if formed artificially, it can be called a clod. Construction aggregate examples * basalt * dolomite * granite * gravel * limestoneSame Day Agg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
