Laterite

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 high iron oxide content. They develop by intensive and prolonged weathering of the underlying parent rock. Tropical weathering (laterization) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. The majority of the land area containing laterites is between the tropics of Cancer and Capricorn.

Laterite has commonly been referred to as a soil type as well as being a rock type. This and further variation in the modes of conceptualizing about laterite (e.g. also as a complete weathering profile or theory about weathering) 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. There is no likelihood, however, that the name will ever be abandoned; for material that looks highly similar to the Indian laterite occurs abundantly worldwide, and it is reasonable to call such material laterite.

Historically, laterite was cut into brick-like 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, and stone. 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 aluminium ore; the ore exists largely in clay minerals and the hydroxides, gibbsite, boehmite, and diaspore, which resembles the composition of bauxite. In Northern Ireland they once provided a major source of iron and aluminium ores. Laterite ores also were the early major source of nickel.

Laterite monument. C 002
Monument of laterite brickstones at Angadipuram, Kerala, India, which commemorates where laterite was first described and discussed by Buchanan-Hamilton in 1807.

Definition and physical description

Da ong Laterite
Laterite in Sơn Tây, Hanoi, Vietnam.

Francis Buchanan-Hamilton first described and named a laterite formation in southern India in 1807.[1]:65 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.[1]:65 The word laterite has been used for variably cemented, sesquioxide-rich soil horizons.[2] A sesquioxide is an oxide with three atoms of oxygen and two metal atoms. It has also been used for any reddish soil at or near the Earth's surface.[2]

Laterite covers are thick in the stable areas of the Western Ethiopian Shield, on cratons of the South American Plate, and on the Australian Shield.[3]:1 In Madhya Pradesh, India, the laterite which caps the plateau is 30 m (100 ft) thick.[4]:554 Laterites can be either soft and easily broken into smaller pieces, or firm and physically resistant. Basement rocks are buried under the thick weathered layer and rarely exposed.[3]:1 Lateritic soils form the uppermost part of the laterite cover. Very good water holding capacity: - Because the particles are so small, the water is trapped between them. - After rain, the water moves into the soil slowly. - Palms are less likely to suffer from drought because the rain water is held in the soil. - However, flooding after heavy rains is more likely. - Nutrient leaching is not likely because the water moves down very slowly. - Nutrients can be washed away from the soil surface easily because the water stays on top of the soil and doesn’t move inside. Large surface of soil particles: - Small clay particles have a large surface area compared to sand particles. - Nutrients stick to clay soils more strongly. - Most clay soils are quite fertile and oil palms need relatively small amounts of fertiliser. Heavy structure: - Because of the tiny particles, the soil sticks together very easily (see Figure 3). - Digging holes or other soil management activities are difficult and should be carried out only on dry soils. - Soil compaction happens easily, especially when the soil is wet. Once compacted, the soil becomes very hard and the oil palm roots cannot grow well. Therefore, it is important to be careful with cattle grazing and with allowing machines such as trucks and excavators into the plantation, especially after rain.

Formation

Laterite-saprolite cross section
Laterite is often located under residual soils.
Estructura-suelo
Soil layers, from soil down to bedrock: A represents soil; B represents laterite, a regolith; C represents saprolite, a less-weathered regolith; below C is bedrock

Tropical weathering (laterization) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils.[5]:3 The initial products of weathering are essentially kaolinized rocks called saprolites.[6] A period of active laterization extended from about the mid-Tertiary to the mid-Quaternary periods (35 to 1.5 million years ago).[5]:3 Statistical analyses show that the transition in the mean and variance levels of 18O during the middle of the Pleistocene was abrupt.[7] It seems this abrupt change was global and mainly represents an increase in ice mass; at about the same time an abrupt decrease in sea surface temperatures occurred; these two changes indicate a sudden global cooling.[7] The rate of laterization would have decreased with the abrupt cooling of the earth. Weathering in tropical climates continues to this day, at a reduced rate.[5]:3

Laterites are formed from the leaching of parent sedimentary rocks (sandstones, clays, limestones); metamorphic rocks (schists, gneisses, migmatites); igneous rocks (granites, basalts, gabbros, peridotites); and mineralised proto-ores;[3]:5 which leaves the more insoluble ions, predominantly iron and aluminium. The mechanism of leaching involves acid dissolving the host mineral lattice, followed by hydrolysis and precipitation of insoluble oxides and sulfates of iron, aluminium and silica under the high temperature conditions[8] of a humid sub-tropical monsoon climate.[9]

An essential feature for the formation of laterite is the repetition of wet and dry seasons.[10] Rocks are leached by percolating rain water during the wet season; the resulting solution containing the leached ions is brought to the surface by capillary action during the dry season.[10] These ions form soluble salt compounds which dry on the surface; these salts are washed away during the next wet season.[10] Laterite formation is favoured in low topographical reliefs of gentle crests and plateaus which prevents erosion of the surface cover.[5]:4 The reaction zone where rocks are in contact with water—from the lowest to highest water table levels—is progressively depleted of the easily leached ions of sodium, potassium, calcium and magnesium.[10] A solution of these ions can have the correct pH to preferentially dissolve silicon oxide rather than the aluminium oxides and iron oxides.[10]

The mineralogical and chemical compositions of laterites are dependent on their parent rocks.[3]:6 Laterites consist mainly of quartz, zircon, and oxides of titanium, iron, tin, aluminium and manganese, which remain during the course of weathering.[3]:7 Quartz is the most abundant relic mineral from the parent rock.[3]:7

Laterites vary significantly according to their location, climate and depth.[8] The main host minerals for nickel and cobalt can be either iron oxides, clay minerals or manganese oxides.[8] Iron oxides are derived from mafic igneous rocks and other iron-rich rocks; bauxites are derived from granitic igneous rock and other iron-poor rocks.[10] Nickel laterites occur in zones of the earth which experienced prolonged tropical weathering of ultramafic rocks containing the ferro-magnesian minerals olivine, pyroxene, and amphibole.[5]:3

Locations

Yves Tardy, from the French Institut National Polytechnique de Toulouse and the Centre National de la Recherche Scientifique, calculated that laterites cover about one-third of the Earth's continental land area.[3]:1 Lateritic soils are the subsoils of the equatorial forests, of the savannas of the humid tropical regions, and of the Sahelian steppes.[3]:1 They cover most of the land area between the tropics of Cancer and Capricorn; areas not covered within these latitudes include the extreme western portion of South America, the southwestern portion of Africa, the desert regions of north-central Africa, the Arabian peninsula and the interior of Australia.[3]:2

Some of the oldest and most highly deformed ultramafic rocks which underwent laterization are found in the complex Precambrian shields in Brazil and Australia.[5]:3 Smaller highly deformed Alpine-type intrusives have formed laterite profiles in Guatemala, Colombia, Central Europe, India and Burma.[5]:3 Large thrust sheets of Mesozoic island arcs and continental collision zones underwent laterization in New Caledonia, Cuba, Indonesia and the Philippines.[5]:3 Laterites reflect past weathering conditions;[2] laterites which are found in present-day non-tropical areas are products of former geological epochs, when that area was near the equator. Present-day laterite occurring outside the humid tropics are considered to be indicators of climatic change, continental drift or a combination of both.[11]

Uses

Agriculture

Laterite soils have a high clay content, which mean they have higher Cation Exchange Capacity and water-holding capacity than sandy soils. It is because the particles are so small, the water is trapped between them. After rain, the water moves into the soil slowly. Palms are less likely to suffer from drought because the rain water is held in the soil. However, if the structure of lateritic soils becomes degraded, a hard crust can form on the surface, which hinders water infiltration, the emergence of seedlings, and leads to increased runoff. It is possible to rehabilitate such soils, using a system called the 'bio-reclamation of degraded lands'. This involves using indigenous water-harvesting methods (such as planting pits and trenches), applying animal and plant residues, and planting high-value fruit trees and indigenous vegetable crops that are tolerant of drought conditions. They are good for oil palm, tea, coffee and cashew cultivation. The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) has employed this system to rehabilitate degraded laterite soils in Niger and increase smallholder farmers' incomes.[12]

Building blocks

Laterite quarry, Angadipuram, India. C 004
Cutting laterite bricks in Angadipuram, India
Pre Rup, Angkor, Camboya, 2013-08-16, DD 04
Example of construction with laterite in Pre Rup, Angkor, Cambodia.

When moist, laterites can easily be cut with a spade into regular-sized blocks.[3]:1 Laterite is mined while it is below the water table, so it is wet and soft.[13] Upon exposure to air it gradually hardens as the moisture between the flat clay particles evaporates and the larger iron salts[10] lock into a rigid lattice structure[13]:158 and become resistant to atmospheric conditions.[3]:1 The art of quarrying laterite material into masonry is suspected to have been introduced from the Indian subcontinent.[14]

After 1000 CE Angkorian construction changed from circular or irregular earthen walls to rectangular temple enclosures of laterite, brick and stone structures.[15]:3 Geographic surveys show areas which have laterite stone alignments which may be foundations of temple sites that have not survived.[15]:4 The Khmer people constructed the Angkor monuments—which are widely distributed in Cambodia and Thailand—between the 9th and 13th centuries.[16]:209 The stone materials used were sandstone and laterite; brick had been used in monuments constructed in the 9th and 10th centuries.[16]:210 Two types of laterite can be identified; both types consist of the minerals kaolinite, quartz, hematite and goethite.[16]:211 Differences in the amounts of minor elements arsenic, antimony, vanadium and strontium were measured between the two laterites.[16]:211

Angkor Wat—located in present-day Cambodia—is the largest religious structure built by Suryavarman II, who ruled the Khmer Empire from 1112 to 1152.[17]:39 It is a World Heritage site.[17]:39 The sandstone used for the building of Angkor Wat is Mesozoic sandstone quarried in the Phnom Kulen Mountains, about 40 km (25 mi) away from the temple.[18] The foundations and internal parts of the temple contain laterite blocks behind the sandstone surface.[18] The masonry was laid without joint mortar.[18]

Road building

Laterite-Casamance
Laterite road near Kounkane, Upper Casamance, Senegal

The French surfaced roads in the Cambodia, Thailand and Viet Nam area with crushed laterite, stone or gravel.[19] Kenya, during the mid-1970s, and Malawi, during the mid-1980s, constructed trial sections of bituminous-surfaced low-volume roads using laterite in place of stone as a base course.[20] The laterite did not conform with any accepted specifications but performed equally well when compared with adjoining sections of road using stone or other stabilized material as a base.[20] In 1984 US$40,000 per 1 km (0.62 mi) was saved in Malawi by using laterite in this way.[20]

Water supply

Bedrock in tropical zones is often granite, gneiss, schist or sandstone; the thick laterite layer is porous and slightly permeable so the layer can function as an aquifer in rural areas.[3]:2 One example is the Southwestern Laterite (Cabook) Aquifer in Sri Lanka.[21]:1 This aquifer is on the southwest border of Sri Lanka, with the narrow Shallow Aquifers on Coastal Sands between it and the ocean.[21]:4 It has considerable water-holding capacity, depending on the depth of the formation.[21]:1 The aquifer in this laterite recharges rapidly with the rains of April–May which follow the dry season of February–March, and continues to fill with the monsoon rains.[21]:10 The water table recedes slowly and is recharged several times during the rest of the year.[21]:13 In some high-density suburban areas the water table could recede to 15 m (50 ft) below ground level during a prolonged dry period of more than 65 days.[21]:13 The Cabook Aquifer laterites support relatively shallow aquifers that are accessible to dug wells.[21]:10

Waste water treatment

In Northern Ireland, phosphorus enrichment of lakes due to agriculture is a significant problem.[22] Locally available laterite—a low-grade bauxite rich in iron and aluminium—is used in acid solution, followed by precipitation to remove phosphorus and heavy metals at several sewage treatment facilities.[22] Calcium-, iron- and aluminium-rich solid media are recommended for phosphorus removal.[22] A study, using both laboratory tests and pilot-scale constructed wetlands, reports the effectiveness of granular laterite in removing phosphorus and heavy metals from landfill leachate.[22] Initial laboratory studies show that laterite is capable of 99% removal of phosphorus from solution.[22] A pilot-scale experimental facility containing laterite achieved 96% removal of phosphorus.[22] This removal is greater than reported in other systems.[22] Initial removals of aluminium and iron by pilot-scale facilities have been up to 85% and 98% respectively.[22] Percolating columns of laterite removed enough cadmium, chromium and lead to undetectable concentrations.[22] There is a possible application of this low-cost, low-technology, visually unobtrusive, efficient system for rural areas with dispersed point sources of pollution.[22]

Ores

K Laterite
Cretaceous iron-rich laterite (the dark unit) in Hamakhtesh Hagadol, southern Israel.

Ores are concentrated in metalliferous laterites; aluminium is found in bauxites, iron and manganese are found in iron-rich hard crusts, nickel and copper are found in disintegrated rocks, and gold is found in mottled clays.[3]:2

Bauxite

Bauxite section on kaolinitic sandstone C 007
Bauxite on white kaolinitic sandstone at Pera Head, Weipa, Australia

Bauxite ore is the main source for aluminium.[1]:65 Bauxite is a variety of laterite (residual sedimentary rock), so it has no precise chemical formula.[23] It is composed mainly of hydrated alumina minerals such as gibbsite [Al(OH)3 or Al2O3 . 3H2O)] in newer tropical deposits; in older subtropical, temperate deposits the major minerals are boehmite [γ-AlO(OH) or Al2O3.H2O] and some diaspore [α-AlO(OH) or Al2O3.H2O].[23] The average chemical composition of bauxite, by weight, is 45 to 60% Al2O3 and 20 to 30% Fe2O3.[23] The remaining weight consists of silicas (quartz, chalcedony and kaolinite), carbonates (calcite, magnesite and dolomite), titanium dioxide and water.[23] Bauxites of economical interest must be low in kaolinite.[6] Formation of lateritic bauxites occurs worldwide in the 145- to 2-million-year-old Cretaceous and Tertiary coastal plains.[24] The bauxites form elongate belts, sometimes hundreds of kilometers long, parallel to Lower Tertiary shorelines in India and South America; their distribution is not related to a particular mineralogical composition of the parent rock.[24] Many high-level bauxites are formed in coastal plains which were subsequently uplifted to their present altitude.[24]

Iron

Absolute iron accumulation in kaolinized basalt. C 015
The dark veins are precipitated iron within kaolinized basalt near Hungen, Vogelsberg, Germany.

The basaltic laterites of Northern Ireland were formed by extensive chemical weathering of basalts during a period of volcanic activity.[9] They reach a maximum thickness of 30 m (100 ft) and once provided a major source of iron and aluminium ore.[9] Percolating waters caused degradation of the parent basalt and preferential precipitation by acidic water through the lattice left the iron and aluminium ores.[9] Primary olivine, plagioclase feldspar and augite were successively broken down and replaced by a mineral assemblage consisting of hematite, gibbsite, goethite, anatase, halloysite and kaolinite.[9]

Nickel

Laterite formation on serpentinite. C 008
Irregular weathering of grey serpentinite to greyish-brown nickel-containing laterite with a high iron percentage (nickel limonite), near Mayagüez, Puerto Rico.

Laterite ores were the major source of early nickel.[5]:1 Rich laterite deposits in New Caledonia were mined starting the end of the 19th century to produce white metal.[5]:1 The discovery of sulfide deposits of Sudbury, Ontario, Canada, during the early part of the 20th century shifted the focus to sulfides for nickel extraction.[5]:1 About 70% of the Earth's land-based nickel resources are contained in laterites; they currently account for about 40% of the world nickel production.[5]:1 In 1950 laterite-source nickel was less than 10% of total production, in 2003 it accounted for 42%, and by 2012 the share of laterite-source nickel was expected to be 51%.[5]:1 The four main areas in the world with the largest nickel laterite resources are New Caledonia, with 21%; Australia, with 20%; the Philippines, with 17%; and Indonesia, with 12%.[5]:4

See also

  • Ferricrete stony particles conglomerated into rock by oxidised iron compounds from ground water
  • Oxisol – A soil type known for occurring in tropical rain forests
  • Plinthosol – Iron-rich soil type

References

  1. ^ a b c Thurston, Edgar (1913). The Madras Presidency, With Mysore, Coorg and the Associated States, Provincial Geographies of India. Cambridge University Press. Retrieved April 6, 2010.
  2. ^ a b c Helgren, David M.; Butzer, Karl W. Butzer (October 1977). "Paleosols of the Southern Cape Coast, South Africa: Implications for Laterite Definition, Genesis, and Age". Geographical Review. 67 (4): 430–445. doi:10.2307/213626. JSTOR 213626.
  3. ^ a b c d e f g h i j k l m Tardy, Yves (1997). Petrology of Laterites and Tropical Soils. ISBN 978-90-5410-678-4. Retrieved April 17, 2010.
  4. ^ Chowdhury, M.K. Roy; Venkatesh, V.; Anandalwar, M.A.; Paul, D.K. (May 11, 1965). Recent Concepts on the Origin of Indian Laterite (PDF) (Report). Geological Survey of India, Calcutta. Archived from the original (PDF) on March 16, 2012. Retrieved April 17, 2010.
  5. ^ a b c d e f g h i j k l m n Dalvi, Ashok D.; Bacon, W. Gordon; Osborne, Robert C. (March 7–10, 2004). The Past and the Future of Nickel Laterites (PDF) (Report). PDAC 2004 International Convention, Trade Show & Investors Exchange. Archived from the original (PDF) on 2009-11-04. Retrieved April 17, 2010.
  6. ^ a b Schellmann, W. "An Introduction in Laterite".
  7. ^ a b Maasch, K.A. (February 1988). "Statistical Detection of the mid-Pleistocene Transition". Climate Dynamics. 2 (3): 133–143. Bibcode:1988ClDy....2..133M. doi:10.1007/BF01053471. ISSN 0930-7575.
  8. ^ a b c Whittington, B.I.; Muir, D. (October 2000). "Pressure Acid Leaching of Nickel Laterites: A Review". Mineral Processing and Extractive Metallurgy Review. 21 (6): 527–599. doi:10.1080/08827500008914177. Retrieved April 17, 2010.
  9. ^ a b c d e Hill, I. G.; Worden, R. H.; Meighan, I. G. (May 1, 2000). "Geochemical evolution of a palaeolaterite: the Interbasaltic Formation, Northern Ireland". Chemical Geology. 166 (1–2): 65–84. Bibcode:2000ChGeo.166...65H. doi:10.1016/S0009-2541(99)00179-5. Archived from the original on February 1, 2013. Retrieved April 6, 2010.
  10. ^ a b c d e f g Yamaguchi, Kosei E. (2003–2004). Iron isotope compositions of Fe-oxide as a measure of water-rock interaction: An example from Precambrian tropical laterite in Botswana (PDF) (Report). Frontier Research on Earth Evolution. 2. p. 3. Retrieved April 17, 2010.
  11. ^ Bourman, R.P. (August 1993). "Perennial problems in the study of laterite: A review". Australian Journal of Earth Sciences. 40 (4): 387–401. Bibcode:1993AuJES..40..387B. doi:10.1080/08120099308728090. Retrieved April 17, 2010.
  12. ^ Bio-reclamation – Converting degraded lateritic soils into productive land, Rural 21, March 2013.
  13. ^ a b Engelhardt, Richard A. New Directions for Archaeological Research on the Angkor Plain: The Use of Remote Sensing Technology for Research into Ancient Khmer Environmental Engineering (Report). UNESCO. p. 8. Archived from the original on 2009-09-22. Retrieved April 17, 2010.
  14. ^ Rocks, David (May 2009). "Ancient Khmer Quarrying of Arkose Sandstone for Monumental Architecture and Sculpture" (PDF). Proceedings of the Third International Congress on Construction History: 1235. Retrieved April 17, 2010.
  15. ^ a b Welch, David. "Archaelological Evidence of Khmer State Political and Economic Organisation". International Archaeological Research Institute. Archived from the original on 2009-09-19. Retrieved April 17, 2010.
  16. ^ a b c d Uchinda, E.; Cunin, O.; Shimoda, I.; Suda, C.; Nakagawa, T. (2003). "The Construction Process of the Angkor Monuments Elucidated by the Magnetic Susceptibility of Sandstone" (PDF). Archaeometry. 45 (2): 221–232. CiteSeerX 10.1.1.492.4177. doi:10.1111/1475-4754.00105. Archived from the original (PDF) on 2011-07-20. Retrieved May 6, 2010.
  17. ^ a b Waragai, Tetsuya; Katagiri, Masao; Miwa, Satoru (2006). A Preliminary Study on the Direction Dependence of Sandstone Column Deterioration in the First Gallery of Angkor Wat (PDF) (Report). Proceedings of the Institute of Natural Sciences, Nihon University. Retrieved May 6, 2010.
  18. ^ a b c Siedel, H.; Plehwe-Leisen, E. v.; Leisen, H. (2008). Salt Load and Deterioration of Sandstone at the Temple of Angkor Wat, Cambodia (PDF) (Report). 11th International Congress on Deterioration and Conservation of Stone, Torun, Poland. I. p. 268. Retrieved May 6, 2010.
  19. ^ Sari, Betti Rosita (2004). "The Trade Route in the Cambodian/Thai Border Areas: Challenges and Opportunities". Journal of Masyarakat Indonesia: 6. Retrieved April 17, 2010.
  20. ^ a b c Grace, Henry (September 1991). "Investigations in Kenya and Malawi using as-dug laterite as bases for bituminous surfaced roads". Journal Geotechnical and Geological Engineering. 9 (3–4): 183–195. doi:10.1007/BF00881740.
  21. ^ a b c d e f g Panabokke, C.R.; Perera, A.P.G.R.L. (January 2005). Groundwater Resources of Sri Lanka (PDF) (Report). Water Resources Board. Retrieved April 17, 2010.
  22. ^ a b c d e f g h i j Wood, R. B.; McAtamney, C.F. (December 1996). "Constructed wetlands for waste water treatment: the use of laterite in the bed medium in phosphorus and heavy metal removal". Hydrobiologia. 340 (1–3): 323–331. doi:10.1007/BF00012776.
  23. ^ a b c d Cardarelli, Francois (2008). Material Handbook: A Concise Desktop Reference. Springer. p. 601. ISBN 9781846286681.
  24. ^ a b c Valeton, Ida (1983). "Palaeoenvironment of lateritic bauxites with vertical and lateral differentiation". Geological Society, London, Special Publications. 11 (1): 77–90. Bibcode:1983GSLSP..11...77V. doi:10.1144/gsl.sp.1983.011.01.10. Retrieved April 17, 2010.
Bhima Kunda

Bhima Kunda (tank) is located beyond the western compound wall of the Bhimesvara Temple precinct, in Kapila Prasad, Old Town, Bhubaneswar. It is now under the care and maintenance of Bhimesvara Temple Development Committee. The tank was excavated by cutting through the laterite bed rock. The embankment is made of dressed laterite blocks.

Bilin, Mon State

Bilin (Burmese: ဘီးလင်းမြို့; Mon: ၜဳက္လေၚ်) is a town in the Mon State of south-east Myanmar. It is the seat of Bilin Township. The Yangon-Mawlamyine Highway passes through Belin. The nearby Belin River flows into the Gulf of Martaban. The majority of residents are Bamar, and there are also members of the Kayin and Pa-O ethnic groups. The majority of people are Buddhist. Belin Township is home to the famous Kyaikhtisaung Pagoda located on a laterite stone hillock near Zoke Thoke village. The hillock itself was formed by laying laterite stones in squares of diminishing size on top of each other.

Champakesvara Siva Temple

Champakesvara Siva Temple is located Ambika Sahi in the Old Town area of Bhubaneswar. It is 157 metres west of Parasuramesvara on the right side of the Kotitirthesvara lane leading to Bindu sagara. It is a laterite temple. Local people believe that the enshrined Siva lingam is patalaphuta and the precinct is the abode of nagas(champa naga) after whom the deity is named as Champakesvara. The local people also believe that the temple precinct which is a den for the snakes do not harm any body.

Dirt road

A dirt road or track is a type of unpaved road made from the native material of the land surface through which it passes, known to highway engineers as subgrade material. Dirt roads are suitable for vehicles; a narrower path for pedestrians, animals, and possibly small vehicles would be called a dirt track—the distinction is not well-defined. Unpaved roads with a harder surface made by the addition of material such as gravel and aggregate (stones), might be referred to as dirt roads in common usage but are distinguished as improved roads by highway engineers. (Improved unpaved roads include gravel roads, laterite roads, murram roads and macadamized roads.)

Compared to a gravel road, a dirt road is not usually graded regularly to produce an enhanced camber to encourage rainwater to drain off the road, and drainage ditches at the sides may be absent. They are unlikely to have embankments through low-lying areas. This leads to greater waterlogging and erosion, and after heavy rain the road may be impassable even to off-road vehicles. For this reason, in some countries, such as Australia and New Zealand, they are known as dry-weather roads.

Dirt roads take on different characteristics according to the soils and geology where they pass, and may be sandy, stony, rocky or have a bare earth surface, which could be extremely muddy and slippery when wet, and baked hard when dry. They are likely to become impassable after rain. They are common in rural areas of many countries, often very narrow and infrequently used, and are also found in metropolitan areas of many developing countries, where they may also be used as major highways and have considerable width.

Terms similar to dirt road are dry-weather road, earth road, or the "Class Four Highway" designation used in the People's Republic of China. A track, dirt track, or earth track would normally be similar but less suitable for larger vehicles.

Geology of Christmas Island

The geology of Christmas Island includes interbedded sequences of carbonates and volcanic rocks formed during the Eocene and Miocene. Reef-wall and lagoonal origin dolomite and limestone are particularly common, along with phosphates such as crandallite, millisite, formed from laterite weathering and apatite and barrandite formed through chemical replacement. Most volcanic rocks are basic and include andesite and limburgite.

Gravel road

A gravel road is a type of unpaved road surfaced with gravel that has been brought to the site from a quarry or stream bed. They are common in less-developed nations, and also in the rural areas of developed nations such as Canada and the United States. In New Zealand, and other Commonwealth countries, they may be known as 'metal roads'. They may be referred to as 'dirt roads' in common speech, but that term is used more for unimproved roads with no surface material added. If well constructed and maintained, a gravel road is an all-weather road.

Khoai

Khoai in Bengali refers to a geological formation specifically in Birbhum, Bardhaman, and Bankura districts of West Bengal, India and some parts of Jharkhand, India that is made up of laterite soil rich in iron oxide, often in the shapes of tiny hills. This is like natural canyon caused by the effect of wind and water erosion on red laterite soil. Khoai is called part of the India's natural heritage.

Lateritic nickel ore deposits

Lateritic nickel ore deposits are surficial, weathered rinds formed on ultramafic rocks.

They account for 73% of the continental world nickel resources and will be in the future the dominant source for the mining of nickel.

List of airports in Chad

This is a list of airports in Chad, grouped by type and sorted by location.

Chad, officially known as the Republic of Chad (French: République du Tchad, Arabic: جمهورية تشاد‎ or Jumhūriyyat Tshād), is a landlocked country in Central Africa. It is bordered by Libya to the north, Sudan to the east, the Central African Republic to the south, Cameroon and Nigeria to the southwest, and Niger to the west. The country is divided into 22 regions, which are further divided into departments and Sub-prefectures.

Chad's capital and largest city is N'Djamena, which is the location of the country's main airport. Scheduled passenger service is available at N'Djamena and five other cities.

Toumaï Air Tchad is the national flag carrier airline, operating domestic services within Chad as well as scheduled international services to other African nations.

Matheran

Matheran is a hill station and a municipal council in Karjat Tahsil in the Raigad district in the Indian state of Maharashtra. It is one of the smallest hill station in India. It is located on the Western Ghats range at an elevation of around 800 m (2,625 feet) above sea level. It is about 90 km far from Mumbai, and 120 km from Pune. Matheran's proximity to many metropolitan cities makes it a popular weekend getaway for urban residents.

Matheran, which means "forest on the forehead" (of the mountains) is an eco-sensitive region, declared by the Ministry of Environment, Forest and Climate Change, Government of India. It is Asia's only automobile-free hill station.There are around 38 designated look-out "points" (viewpoints) in Matheran, including the Panorama Point that provides a 360-degree view of the surrounding area and also the Neral town. From this point, the view of sunset and sunrise is dramatic. The Louisa Point offers crystal clear view of the Prabal Fort. The other points are the One Tree Hill Point, Heart Point, Monkey Point, Porcupine Point, Rambagh Point, and more. To stay there, there are plenty of hotels. There are many Parsi bungalows. Beautiful old British-style architecture is preserved in Matheran. The roads are not metalled and are made of red laterite earth.

Muthapudupet

Muthapudupet is a city near to Chennai in the Chennai district and comes under Chennai Metropolitan area Muthapudupet is around 8 kilometers from Avadi.

Areas around Muthapudupet were once paddy fields, fruit farms, lakes, swamps and forests. Now the field areas have shrunk and residential plots have sprung up. Highest Natural point is 60 m above Mean Sea level. The soil is sandy and instantial laterite, mostly Recent Alluvium. Geological formations are concealed by Recent alluvium, with little or no exposure of rocks, most formations being Archean and tertiary sediments. Alluvial deposits of thickness of 28 meters, can amplify ground shaking during Tremors.

Muthapudupet is a predominantly Tamil speaking area with sizable Telugu speakers. Most people here are Multilingual, Speaking Tamil, Mothertongue and Hindi/English. One can find people from every region of India in Muthapudupet-Mittanamallee. Thanks to nearby Defence/Central Government Establishments. Central Government is the largest employer in Muthapudupet.

A new Tidel park will be coming up at near Muthapudupet (Pattabiram, Avadi) in MTH road. So many people of the nearby areas will get job opportunity. The land value of Muthapudupet, Palavedu, Pattabiram, Avadi and some nearby areas will increase fastly due to coming up of Tidel park (IT park information technology).

Oxisol

Oxisols are an order in USDA soil taxonomy, best known for their occurrence in tropical rain forest, 15–25 degrees north and south of the Equator. In the World Reference Base for Soil Resources (WRB), they belong mainly to the Ferralsols, but some are Plinthosols or Nitisols. Some Oxisols have been previously classified as laterite soils.

Phanom Rung Historical Park

Phanom Rung (Thai: พนมรุ้ง, pronounced [pʰānōm rúŋ]), or full name, Prasat Hin Phanom Rung (Thai: ปราสาทหินพนมรุ้ง – Phanom Rung Stone Castle), is a Hindu Khmer Empire temple complex set on the rim of an extinct volcano at 402 metres (1,319 ft) elevation. It is located in Buriram Province in the Isan region of Thailand, and was built at a time when Khmer social-political influences were significant in Srisaket. It was built of sandstone and laterite between the 10th and 13th centuries. It was a Hindu shrine dedicated to Shiva, and symbolises Mount Kailash, his heavenly dwelling.

Thailand's Department of Fine Arts spent 17 years restoring the complex to its original state from 1971 to 1988. On 21 May 1988, the park was officially opened by Princess Maha Chakri Sirindhorn. In 2005, the temple was submitted to UNESCO for consideration as a future World Heritage Site.

Phra That Dum

Phra That Dum (Thai:พระธาตุดุม) is located at Tambon Ngew Don Sakon Nakhon Province, 3 kilometres from town on the way to Phatthana Suksa School. There were originally 3 brick Khmer pagodas on the same laterite base but only one stands today. The pagodas were built in the 16th Buddhist Century.

Phra That Dum is the lone Stupa is built with laterite in the same period as Phra That Narai Cheng Weng, but the stupa is smaller without base. The lintel featuring God Vishnu in reclining position is placed on the northern arch. Furthermore, there are carving regarding gods riding different animals over the Rahu.

Phra That Narai Cheng Weng

Phra That Narai Cheng Weng or Phra That Narai Jengveng (Thai:พระธาตุนารายณ์เจงเวง) - is located at Amphur Muang Sakon Nakhon Province, the stupa is built from sandstone on a laterite base and carved beautifully. Its lintel features Lord Krisna killing Lion in Bapuan Khmer art. The art appearing on this stupa is quite similar to many other Khmer ruins found in Isan.

This khmer sanctuary is 5 kilometres from town on the way to Udon Thani. The sandstone pagoda is on a laterite base. Ornate designs adorn the lintel, doorway and windows. It is believed the site was entirely constructed by women who competed with the men who built Phra That Phu Pek. It dates from the 16th-17th Buddhist century.

Phra That Phu Pek

Phra That Phu Pek (Thai:พระธาตุภูเพ็ก) is an ancient temple in Sakon Nakhon Province, in the Isan region of Thailand. This ancient Khmer ruin was built from sandstone, standing on a laterite base. This is a Buddhist temple ruin of Khmer origin in the form of a chedi, it was built in the 16th-17th Buddhist century. The ruin is special as it houses a solar calendar, a cube-shaped rock, in its stupa. The ancients used it for indicating the position of the sun, important for religious rites and agricultural seasons.

Phra That Phu Pek is in tambon Na Hua Bo, Phanna Nikhom district, Sakon Nakhon Province of northeastern Thailand, about 37 km west of the town of Sakon Nakhon. The temple is in Phu Phan National Park, in the Phu Phan Mountains. To get there, take the Sakon Nakhon-Udon Thani road for 22 kilometres and take a road on the left for 14 kilometres, then ascend 491 steps. The laterite pagoda is on a square base, seemingly unfinished because it has no roof or pagoda top.

Santoshgad

Santoshgad (also referred to as Tathavade, the name of the closest village) is a fort in Phaltan taluka of Satara districtin Maharashtra, India

Tathavade or Santoshgad hill fort (Phaltan T; 17� 57' N, 74� 20' E; RS. Lonand, 2.9 m.) lies in the north-west corner of the Phaltan Taluka, about 12 miles south-west of Phaltan, the taluka headquarters! The fort is now easily approachable throughout the year as the Public Works Department has recently constructed a pucca road from village Tathavade lying at the foot of the hill. The fort is roughly triangular in shape. The hill on which it stands is a little lower than the main range. The apices of the triangle are north-west and south-east making it nearly equilateral. At the foot on the northern side lies the village of Tathavade (p. 1,001) with people nearly all cultivators mostly Ramoshis and Marathas. The defences consist of three walls, the top wall going all round the hill and forming what may be called the citadel. It surmounts a perpendicular scarp of black rock about thirty feet high, and is itself about fifteen feet higher. In thickness it is twenty feet and had originally a parapet about six feet high and three feet thick, all of which has broken down. It is made of laterite blocks from one or two cubic feet each, and solidly set in mortar, lined with small stones and mud. It is carefully provided at intervals with secret escape doors for the garrison should the fort be successfully taken. It is especially strong at the three angles from which project triangular outworks about sixty feet lower than the citadel. The outworks are of unequal size, but built of the same materials and more strongly even than the citadel. The sides of the south-west out-work are not more than thirty yards long but it is perhaps the most solid of the three; the sides of the north-east outwork are about fifty yards, and those of the north-west out-work about seventy yards long. The first two out-works communicated with the citadel by a small door not more than two feet wide built through the walls, which led on to the steps cut in the scarp. The citadel wall has a gap at the north-west angle which formed the communication with the north-west out-work. On the north-east side of this was the main gateway about five feet wide, also made of laterite, of beautifully cut massive masonry. It faced, and was sheltered by a projecting bastion. The north side of the hill was partly protected for about a hundred feet by two lower walls or terraces, the one below the other with bastions at intervals. They are of much lighter workmanship than the blocks in rough mortar and the lining of uncut stones and mud. These walls both run east and west along the entire length of the northern face of the hill. They then turn through an angle of over 90 degrees, and are taken up the hill to meet the walls above them. The upper of the two is broken by a gateway of trap facing east, like the upper gateway, similarly sheltered, and otherwise like it, but of far less strength and of much rougher workmanship. The lowest wall is divided by a gap of full thirty feet in the centre flanked by two strong bastions, but no gateway. The ascent between these three entrances and from the north-west out-work on to the citadel is by a winding path with steps at intervals where, not unfrequently, the naked scarp of the rock has to be surmounted. The steps are nearly everywhere broken down and the way generally blocked with prickly pear. The above description will show that the hill was unprotected below the citadel and its out-works on the south-west and south-east sides, and that elaborate care was taken to protect the north side. There seems to be no special reason for this difference except that the entrance and therefore the weakest point of the citadel was on the north side. By making the two gateways face east and protecting them with projections of the wall, their assault was impeded while it was impossible to hit them directly with cannon shot from the plain below, which, according to tradition, was a special point in the fortification of the day. In sieges it was apparently the fashion to direct a cannonade first against the gate and to provide a force to rush through if the besiegers succeeded in bursting it. The difficulties of elsewhere penetrating or escalading hill forts such as these, were probably and not wrongly thought insuperable, bribery and stratagem apart. The citadel is not more than 600 yards round and its area not much more than twenty acres. There were originally but few buildings. The headquarters or sadar was a building about fifty feet by thirty feet including its two otas or verandahs. It opened to the north and besides accommodating the treasury, was used as a sort of court-house for the subhedar in charge of the fort. Next to it on the west was a stone building about forty feet by twenty, with walls three feet thick, and a roof on the south side made of brick coated with cement. It contained three chambers for storage of grain, treasure and gunpowder. The east chamber still remains. Immediately south of the east chamber is the great pond, cut some sixty to seventy feet down into the rock, and the sides smoothed off with great care. It holds a tolerable supply of water, but is fed by no spring. It is about twenty-five to thirty feet square and has steps on the eastern side leading down to the water's edge. Halfway down at a landing and turn of the steps is a small temple of Tatoba Mahadev from whom the fort takes its name. This large pond was apparently the only source of the water-supply of the citadel. It has been much choked with silt, and is said to hold much less water than before, much probably leaking down through the laterite. The rest of the citadel is so blocked with prickly pear that no other buildings can be distinguished. The hill top has room only for very few. One is a mosque for Musalmans. The north-east out-work has some buildings while, inside the two lower walls, are others all in ruins. Outside the lowest entrance is pointed out the side of the elephant-house, fit for not more than two beasts. On the saddle back between the southern angle and the main range of hills has been cut a gap with remains of buildings said to have been the grass stacks of the fort. The grass was supplied chiefly from lands on the plateau above the Mahadev range and brought for storage to this spot. It is more than two hundred yards from the fort and is hardly convenient than the village itself which is at least as accessible as the fort. Immediately inside and directely facing the lowest entrance is a large cave pond. Its mouth has been almost wholly blocked with rubbish. A descent of some six feet is therefore necessary to reach the water. The excavation is partly natural but evidently enlarged artificially. The exact size of the cave pond cannot be made out. Three massive pillars appear supporting the roof. The rock is laterite and hence no doubt the abundant supply of excellent water filters from above. The upper fort is nearly all made of laterite with no traces of quarrying about. It seems therefore not improbable that the ponds were excavated by the fort builders and the stone used for the fort walls. There are four other similar ponds completely blocked up. Their stone and that of the big pond on the top would amply suffice for the external work considerable as it is. The mildew of this laterite is used by the people as a tonic for women after child-birth. It probably contains some principle of iron. It is a belief in the village that the large pond in the citadel and this cave pond are connected by a passage now choked up, and that a lemon thrown into the water of the one used in former times to appear on the surface of the other. These ponds show that the hill internally is made of laterite with an outer coating of trap, thin at the sides but on the top some forty feet thick.

The name of this village is traditionally derived from Tatoba, a sage who took up his abode on the fort hill. The cave pond is said to have been made by him, and the small temple of Mahadev in the big pond is named after him. The local tradition is that this fort was built by Shivaji the Great (1630–80). In 1666 it was in the hands of Bajaji Naik Nimbalkar. In the same year Chhatrapati Shivaji after the treaty of Purandhar served under Jaysing, the Rajput general of Aurangzeb's army, against Bijapur and with his Mavlas escaladed Tathavade. [Grant Duffs Marathas, Vol. I, 165.] The Bijapur Government again apparently got it back from the Moghals probably by treaty. Chhatrapati Shivaji retook it for himself in 1673 [Grant Duffs Marathas, Vol. I, 202.] and in 1676 he had to retake the open country in its neighbourhood, the estate-holders of which were always ready to rebel against him.[ Grant Duffs Marathas, Vol. I, 209.] The fort was taken by the Moghals in 1689. [Grant Duffs Marathas, Vol. I, 273.]. but was ceded to Shahu in 1720 in the imperial grants made to him in that year. [Grant Duffs Marathas, Vol. I, 339] In a revenue statement of about 1790 Tathora appears as the head of a sub-division in the Nahisdurg sarkar with a revenue of Rs. 1,120. [Warring's Marathas, 244.] The fort remained in the hands of the Marathas till 1818 when it was shelled by a detachment of General Pritzler's army from the plateau and a spur pointed out about half a mile to the west. A good many of the buildings and part of the walls are said to have been injured by the shelling. The commandant fled at the first few shots, the garrison followed, and the fort was taken. Its elaborate design and considerable strength for the times in which it was built may be explained by the fact that it was close to the Nizam Shahi frontier and of some importance therefore to the Bijapur government, while the constant disturbances in the neighbourhood in Chhatrapati Shivajis time would amply account for any additions he made to it.

A story is told that the famous dacoit Umaji Naik (1827) was resting at a spring in the ravine which leads down to the fort from the plateau and that a Brahman on his way to Tathavad passed by with a little grain given him in charity. Umaji called on him to stand and give up what he had. But when he learnt that it was only grain sent him off in peace, entreated his blessings, and gave him Rs. 25.

Terrey Hills, New South Wales

Terrey Hills is a suburb of northern Sydney, in the state of New South Wales, Australia 25 kilometres north of the Sydney central business district in the local government area of Northern Beaches Council. It is part of the Northern Beaches region. Terrey Hills is also considered to be part of the Forest District, colloquially known as The Forest.

Terrey Hills is a very leafy suburb and in some areas semi-rural, with many people boarding their horses in the area. Terrey Hills owes its name to the two original land holders Samuel Hills and Obediah James Terrey. Obediah Terrey acquired 640 acres (2.6 km2) in 1881 and Samuel Hills owned 100 acres (0.40 km2) nearby.The area was used by Aborigines prior to European settlement, and rock carvings exist in some places. One set of carvings is located near Larool Road and depicts hunting scenes with kangaroos, human figures and footprints. Terrey Hills Post Office opened on 17 June 1935.

Uttaresvara Siva Temple

Uttaresvara Siva Temple is a 12th-century Hindu temple dedicated to Lord Siva located in Bhubaneswar, Orissa, India.

USDA soil taxonomy
World Reference Base
for Soil Resources
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