1.
Laterite
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Laterite is a soil and rock type rich in iron and aluminium, and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of iron oxide content. They develop by intensive and long-lasting weathering of the parent rock. Tropical weathering is a process of chemical weathering which produces a wide variety in the thickness, grade, chemistry. The majority of the area containing laterites is between the tropics of Cancer and Capricorn. Laterite has commonly referred to as a soil type as well as being a rock type. This and further variation in the modes of conceptualizing about laterite has led to calls for the term to be abandoned altogether, at least a few researchers specializing in regolith development have considered that hopeless confusion has evolved around the name. Historically, laterite was cut into shapes and used in monument-building. After 1000 CE, construction at Angkor Wat and other southeast Asian sites changed to rectangular temple enclosures made of laterite, brick, since the mid-1970s, some trial sections of bituminous-surfaced, low-volume roads have used laterite in place of stone as a base course. Thick laterite layers are porous and slightly permeable, so the layers can function as aquifers in rural areas, locally available laterites have been used in an acid solution, followed by precipitation to remove phosphorus and heavy metals at sewage-treatment facilities. Laterites are a source of ore, the ore exists largely in clay minerals and the hydroxides, gibbsite, boehmite, and diaspore. In Northern Ireland they once provided a source of iron. Laterite ores also were the major source of nickel. Francis Buchanan-Hamilton first described and named a laterite formation in southern India in 1807 and he named it laterite from the Latin word later, which means a brick, this highly compacted and cemented soil can easily be cut into brick-shaped blocks for building. The word laterite has been used for variably cemented, sesquioxide-rich soil horizons, a sesquioxide is an oxide with three atoms of oxygen and two metal atoms. It has also used for any reddish soil at or near the Earths surface. Laterite covers are thick in the areas of the Western Ethiopian Shield, on cratons of the South American Plate. In Madhya Pradesh, India, the laterite which caps the plateau is 30 m thick, laterites can be either soft and easily broken into smaller pieces, or firm and physically resistant
2.
Regolith
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Regolith is a layer of loose, heterogeneous superficial material covering solid rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, Mars, some asteroids, the term regolith combines two Greek words, rhegos, blanket, and lithos, rock. Merrill first defined the term in 1897, writing, In places this covering is made up of material originating through rock-weathering or plant growth in situ, in other instances it is of fragmental and more or less decomposed matter drifted by wind, water or ice from other sources. This entire mantle of unconsolidated material, whatever its nature or origin, biota and organic components derived from it. Regolith can vary from being essentially absent to hundreds of metres in thickness and its age can vary from instantaneous to hundreds of millions of years old. Regolith on Earth originates from weathering and biological processes, if it contains a significant proportion of biological compounds it is conventionally referred to as soil. People also call various types of earthly regolith by such names as dirt, dust, gravel, sand, Regolith is also important to engineers constructing buildings, roads and other civil works. The mechanical properties of regolith vary considerably and need to be documented if the construction is to withstand the rigors of use, Regolith may host many mineral deposits, for example mineral sands, calcrete uranium, and lateritic nickel deposits, among others. Elsewhere, understanding regolith properties, especially geochemical composition, is critical to geochemical and geophysical exploration for mineral deposits beneath it, the regolith is also an important source of construction material, including sand, gravel, crushed stone, lime, and gypsum. The regolith is the zone through which aquifers are recharged and through which aquifer discharge occurs, many aquifers, such as alluvial aquifers, occur entirely within regolith. The composition of the regolith can also strongly influence water composition through the presence of salts, Regolith covers almost the entire lunar surface, bedrock protruding only on very steep-sided crater walls and the occasional lava channel. The impact of micrometeoroids, sometimes travelling faster than 96,000 km/h and this melting and refreezing welds particles together into glassy, jagged-edged agglutinates, reminiscent of tektites found on Earth. The regolith is generally from 4 to 5 m thick in mare areas, below this true regolith is a region of blocky and fractured bedrock created by larger impacts, which is often referred to as the megaregolith. The density of regolith at the Apollo 15 landing site averages approximately 1.35 g/cm3 for the top 30 cm, and it is approximately 1. 85g/cm3 at a depth of 60 cm. The term lunar soil is used interchangeably with lunar regolith but typically refers to the finer fraction of regolith. Some have argued that the soil is not correct in reference to the Moon because soil is defined as having organic content. However, standard usage among lunar scientists is to ignore that distinction, lunar dust generally connotes even finer materials than lunar soil, the fraction which is less than 30 micrometers in diameter. The average chemical composition of regolith might be estimated from the concentration of elements in lunar soil
3.
Weathering
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Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earths atmosphere, waters, and biological organisms. Two important classifications of weathering processes exist – physical and chemical weathering, mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice and pressure. While physical weathering is accentuated in very cold or very dry environments, chemical reactions are most intense where the climate is wet, however, both types of weathering occur together, and each tends to accelerate the other. For example, physical abrasion decreases the size of particles and therefore increases their surface area, the various agents act in concert to convert primary minerals to secondary minerals and release plant nutrient elements in soluble forms. The materials left over after the rock breaks down combined with organic material creates soil, in addition, many of Earths landforms and landscapes are the result of weathering processes combined with erosion and re-deposition. Physical weathering, also recognized as mechanical weathering, is the class of processes that causes the disintegration of rocks without chemical change, the primary process in physical weathering is abrasion. However, chemical and physical weathering often go hand in hand, physical weathering can occur due to temperature, pressure, frost etc. For example, cracks exploited by physical weathering will increase the area exposed to chemical action. Abrasion by water, ice, and wind loaded with sediment can have tremendous cutting power, as is amply demonstrated by the gorges, ravines. In glacial areas, huge moving ice masses embedded with soil and rock fragments grind down rocks in their path, plant roots sometimes enter cracks in rocks and pry them apart, resulting in some disintegration, Burrowing animals may help disintegrate rock through their physical action. However, such influences are usually of importance in producing parent material when compared to the drastic physical effects of water, ice, wind. Physical weathering is called mechanical weathering or disaggregation. Thermal stress weathering results from the expansion and contraction of rock, for example, heating of rocks by sunlight or fires can cause expansion of their constituent minerals. As some minerals expand more than others, temperature changes set up differential stresses that cause the rock to crack apart. Because the outer surface of a rock is often warmer or colder than the more protected inner portions and this process may be sharply accelerated if ice forms in the surface cracks. When water freezes, it expands with a force of about 1465 Mg/m^2, disintegrating huge rock masses, thermal stress weathering comprises two main types, thermal shock and thermal fatigue. Thermal stress weathering is an important mechanism in deserts, where there is a diurnal temperature range, hot in the day. The repeated heating and cooling exerts stress on the layers of rocks
4.
Soil horizon
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A soil horizon is a layer generally parallel to the soil crust, whose physical characteristics differ from the layers above and beneath. Each soil type usually has three or four horizons, Horizons are defined in most cases by obvious physical features, chiefly colour and texture. These may be described both in terms and in terms relative to the surrounding material. The differentiation of the soil into distinct horizons is largely the result of influences, such as air, water, solar radiation and plant material, the World Reference Base for Soil Resources lists 40 diagnostic horizons. Soil scientists often dig a hole, called a soil pit to expose soil horizons for study. The vertical section exposing a set of horizons, from the surface to the parent rock, is termed a soil profile. Most soils, especially in climates, conform to a similar general pattern of horizons. Each main horizon is denoted by a letter, which may then be followed by several alphanumerical modifiers highlighting particular outstanding features of the horizon. While the general O-A-B-C-R sequence seems fairly universal, some variation exists between the systems in different parts of the world. It should be emphasised that no one system is more correct – as artificial constructs, also, many subtropical and tropical areas have soils such as oxisols or aridisols that have very different horizons from ideal soil, or no horizons at all. Six master soil horizons are commonly recognized and are designated using the capital letters O, A, E, B, C, the following horizons are listed by their position from top to bottom within the soil profile. Not all of these layers are present in every location, for instance, P horizons only form in areas that have been waterlogged for long periods of time. Soils with a history of human interference, for instance through major earthworks or regular deep ploughing, the horizon not listed is the O horizon which is grass and animal/plant life. Several systems of soil horizon classification exist, the most well known and widely used is the A-B-C system, first used in Russia by Dokuchaev in the late 19th century in his description of Chernozem soils. Other systems exist, including the systems of diagnostic horizons employed by USDA Soil Taxonomy, at perhaps the most fundamental level, distinction can be made between mineral soil horizons and organic soil horizons. Dokuchaev was the first to label soil horizons with A, B and C designations, according to Nikiforoff, Dokuchaevs A horizon was the surface humus horizon, his B horizon was the second horizon and graded to the C horizon, which was the relatively unweathered parent material. This layer generally forms above the soil or occurs in an organic soil profile. The O stands for organic matter and it is a surface layer dominated by the presence of large amounts of organic material derived from dead plant and/or animal residues which is in varying stages of decomposition
5.
Ferric
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Ferric refers to iron-containing materials or compounds. In chemistry the term is reserved for iron with an number of +3. On the other hand, ferrous refers to iron with oxidation number of +2, iron is usually the most stable form of iron in air, as illustrated by the pervasiveness of rust, an insoluble iron-containing material. The word ferric is derived from the Latin word ferrum for iron, examples include iron-sulfur clusters, oxyhemoglobin, ferritin, and the cytochromes. The bioavailability of iron is of great interest because all forms of life require iron. Iron-deficiency anemia illustrates the problems resulting from low iron intake, many foods contain soluble iron compounds and are therefore necessary for good nutrition. The low bioavailability of iron affects all forms of life, bacteria secrete iron-attracting agents called siderophores that form soluble compounds of iron that can be reabsorbed into the cell and used in building iron-containing metalloproteins. The impact of increasing the bioavailability of iron was famously demonstrated by an experiment where an area of the ocean surface was sprayed with iron salts. After several days, the phytoplankton within the treated area bloomed to such an extent that the effect was visible from outer space and this fertilizing process has been proposed as a means to mitigate the carbon dioxide content of the atmosphere. Ferric iron mitigates the eutrophication of lakes by reducing the bioavailability of phosphorus in the water, mitigation arises because ferric phosphate is insoluble. Like iron, phosphate is often a limiting nutrient, and its reduction in concentration from solution limits the growth of algae, in water, ferric iron forms compounds that are often insoluble, at least near neutral pH. A salt of ferric iron hydrolyzes water and produces iron oxide-hydroxides while contributing hydrogen ions to the solution, in contrast, typical Na+ salts dissolve in water without lowering the pH. Aluminium behaves similarly to ferric ion, rust, a mixture of ferric hydroxide compounds, illustrates the low solubility of ferric ions in water. Various reagents cause rust to dissolve even at neutral pH and these ligands include EDTA, which forms a chelate complex with the ion, displacing the hydroxide and oxide ligands that comprise rust. For this reason, EDTA is often used to iron deposits or to deliver soluble iron in fertilizers. Citrate also solubilizes ferric ion at neutral pH, although its complexes are less stable than those of EDTA, Ferric iron is a d5 center, meaning that the metal has five valence electrons in the 3d orbital shell. The magnetism of ferric compounds is determined by these five electrons. Usually ferric ions are surrounded by six ligands arranged in octahedron, sometimes three and sometimes as many as seven ligands are observed
6.
Erosion
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In earth science, erosion is the action of surface processes that remove soil, rock, or dissolved material from one location on the Earths crust, then transport it away to another location. Eroded sediment or solutes may be transported just a few millimetres, the rates at which such processes act control how fast a surface is eroded. Feedbacks are also possible between rates of erosion and the amount of eroded material that is carried by, for example. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, while erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the rate of erosion in the region. Excessive erosion causes both on-site and off-site problems, on-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of bodies, as well as sediment-related damage to roads. Intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, however, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, and the surface runoff which may result from rainfall, produces four types of soil erosion, splash erosion, sheet erosion, rill erosion. Splash erosion is generally seen as the first and least severe stage in the erosion process. In splash erosion, the impact of a falling raindrop creates a crater in the soil. The distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rate is greater than the rate at which water can infiltrate into the soil. If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope, sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes, generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimetres or less and this means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow
7.
Tropical climate
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A tropical climate in the Köppen climate classification it is a non-arid climate in which all twelve months have mean temperatures of at least 18 °C. In tropical climates there is only two seasons, a wet season and a dry season. Tropical climates are frost-free and changes in the angle are small. In tropical climates temperature remains constant throughout the year. Within the tropical climate there are distinct varieties based on precipitation, In the Tropical rainforest climate. These climates usually occur within 5–10° latitude of the equator, in some eastern coast areas, they may extend to as much as over 26° away from the equator. This climate is dominated by the doldrums Low Pressure System all year round and it is dominated by the monsoon winds which change direction according to the seasons. This climate has a driest month with less than 60 millimetres. Examples, Southern part of Arabian Peninsula, mountaintops within the tropics, e. g. Mount Kenya, can be cold. However, like lowlands in the tropics, there is seasonal variation of temperature. Because of the effect of sun angle on climate most areas within the tropics are hot year-round, the ITCZ is shown, for July average, in the graphic. Areas of ascending air have heavy rainfall, areas of descending air are dry, the ITCZ somewhat follows the solar equator throughout the year, but with geographical variations, and in some areas is heavily influenced by local large-scale monsoons
8.
Temperate climate
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In geography, temperate or tepid latitudes of Earth lie between the tropics and the polar regions. The temperatures in these regions are relatively moderate, rather than extremely hot or cold. The north temperate zone extends from the Tropic of Cancer to the Arctic Circle, the south temperate zone extends from the Tropic of Capricorn to the Antarctic Circle. In some climate classifications, the zone is often divided into several smaller climate zones. These include Humid subtropical climate, Mediterranean climate, oceanic, subtropical climates are located between 23. 5° and 35. 0° north or south latitude on the eastern or leeward sides of landmasses. This climate has long, generally hot, summers and short, mild winters and these climates may occur in southern Asia, the southeastern United States, parts of eastern Australia, and in eastern coastal South America. Mediterranean climates, occur between 30° and 42° north and south latitude, on the sides of landmasses. This climate has hot summers and short mild winters, however, seasonal rainfall is the opposite of that of the subtropical humid type. These climates occur near the rimlands of the Mediterranean Sea, in western Australia, in California, the oceanic climates occur in the higher middle latitudes, between 45° and 60° north and south latitude. They are created by the flow from the cool high latitude oceans to their west. This causes the climate to have cool summers and cool winters, annual rainfall is spread throughout the entire year. Regions with this climate include Western Europe, northwestern North America, the Continental climates occur in middle latitudes, between 35° or 40° to 55°. These climates are normally inland or on sides of landmasses. They feature warm to hot summers and cold winters, with a large temperature variation. Regions with this climate include northern temperate Asia, the northern United States, southern Canada, the vast majority of the worlds human population resides in temperate zones, especially in the northern hemisphere, due to its greater mass of land. The richest temperate flora in the world is found in southern Africa, geographical zone Habitat Köppen climate classification Middle latitudes Polar circle Subtropics
