Misplaced Pages

#188811

55-631: The Khleangs are two buildings of unknown purpose on the east side of the Royal Square in Angkor Thom , Cambodia , located just behind the twelve towers of Prasat Suor Prat and separated by the royal route that leads from the Angkor Thom Royal Palace to the Victory Gate. They are oriented along the north-south axis. The two were not built at the same time—the northern building (North Khleang)

110-488: A crust , a mottled zone and a pallid zone. He cautions strongly against the concept of "lateritic deep weathering" since "it begs so many questions". 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 initial products of weathering are essentially kaolinized rocks called saprolites . A period of active laterization extended from about

165-399: A central tower and oriented towards the east. Within the city was a system of canals , through which water flowed from the northeast to the southwest. The bulk of the land enclosed by the walls would have been occupied by the secular buildings of the city, of which nothing remains. This area is now covered by forest. Most of the great Angkor ruins have vast displays of bas-relief depicting

220-493: A high clay content, which means they have higher cation exchange capacity , low permeability, high plasticity and high water-holding capacity than sandy soils. It is because the particles are so small, the water is trapped between them. After the rain, the water moves into the soil slowly. Due to intensive leaching, laterite soils lack in fertility in comparison to other soils, however they respond readily to manuring and irrigation. Palms are less likely to suffer from drought because

275-438: A major source of iron and aluminum ore. Percolating waters caused degradation of the parent basalt and preferential precipitation by acidic water through the lattice left the iron and aluminum ores. 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 . Laterite ores were

330-540: A major source of iron and aluminum ores. Laterite ores also were the early major source of nickel . Francis Buchanan-Hamilton first described and named a laterite formation in southern India in 1807. 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

385-579: A parapet on the top. There are gates at each of the cardinal points , from which roads lead to the Bayon at the centre of the city. As the Bayon itself has no wall or moat of its own, those of the city are interpreted by archaeologists as representing the mountains and oceans surrounding the Bayon's Mount Meru . Another gate—the Victory Gate—is 500 m north of the east gate; the Victory Way runs parallel to

440-466: A sudden global cooling. 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. 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 mineralized proto-ores; which leaves

495-609: Is 45 to 60% Al 2 O 3 and 20 to 30% Fe 2 O 3 . The remaining weight consists of silicas (quartz, chalcedony and kaolinite ), carbonates ( calcite , magnesite and dolomite ), titanium dioxide and water. Bauxites of economical interest must be low in kaolinite. Formation of lateritic bauxites occurs worldwide in the 145- to 2-million-year-old Cretaceous and Tertiary coastal plains. The bauxites form elongate belts, sometimes hundreds of kilometers long, parallel to Lower Tertiary shorelines in India and South America; their distribution

550-404: Is a possible application of this low-cost, low-technology, visually unobtrusive, efficient system for rural areas with dispersed point sources of pollution. Ores are concentrated in metalliferous laterites; aluminum 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. Bauxite ore

605-428: Is a soil 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 , usually when there are conditions of high temperatures and heavy rainfall with alternate wet and dry periods. The process of formation

SECTION 10

#1732859242189

660-599: Is also widely used in Brazil for road building. 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. One example is the Southwestern Laterite (Cabook) Aquifer in Sri Lanka. This aquifer is on the southwest border of Sri Lanka, with the narrow Shallow Aquifers on Coastal Sands between it and

715-768: 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. 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 . In Madhya Pradesh , India, the laterite which caps the plateau is 30 m (100 ft) thick. Laterites can be either soft and easily broken into smaller pieces, or firm and physically resistant. Basement rocks are buried under

770-418: Is believed to be the correct one, due to neglect of calling it in incorrect pronunciation. The word Nokor ( Khmer : នគរ , Nôkô ) is literally derived from Sanskrit word of Nagara ( Devanāgarī : नगर), which means City , combining with Khmer word Thom ( Khmer : ធំ , Thum ), which means Big or Great so as to form Nokor Thom then being altered to current name of Angkor Thom . Angkor Thom

825-422: Is called laterization . Tropical weathering 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

880-412: Is not related to a particular mineralogical composition of the parent rock. Many high-level bauxites are formed in coastal plains which were subsequently uplifted to their present altitude. The basaltic laterites of Northern Ireland were formed by extensive chemical weathering of basalts during a period of volcanic activity. They reach a maximum thickness of 30 m (100 ft) and once provided

935-498: Is the main source of aluminum. It is a variety of laterite (residual sedimentary rock), so it has no precise chemical formula. It is composed mainly of hydrated alumina minerals such as gibbsite [Al(OH) 3 or Al 2 O 3 . 3H 2 O)] in newer tropical deposits; in older subtropical, temperate deposits the major minerals are boehmite [γ-AlO(OH) or Al 2 O 3 .H 2 O] and some diaspore [α-AlO(OH) or Al 2 O 3 .H 2 O]. The average chemical composition of bauxite, by weight,

990-498: The Atlantis of Plato ". It is believed to have sustained a population of 80,000–150,000 people. The Poem of Angkor Wat composed in Khmer verse in 1622 describes the beauty of Angkor Thom. Angkor Thom is in the Bayon style. This manifests itself in the large scale of the construction, in the widespread use of laterite , in the face-towers at each of the entrances to the city and in

1045-539: The naga -carrying giant figures which accompany each of the towers. The city lies on the west bank of the Siem Reap River , a tributary of Tonle Sap , about a quarter of a mile from the river. The south gate of Angkor Thom is 7.2 km north of Siem Reap , and 1.7 km north of the entrance to Angkor Wat . The walls, 8 m high and flanked by a moat , are each 3 km long, enclosing an area of 9 km². The walls are of laterite buttressed by earth, with

1100-504: The subsoils of the equatorial forests, of the savannas of the humid tropical regions, and of the Sahelian steppes . 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

1155-471: The " roundels on pilasters on the south side of the west entrance are unusual in design." What one sees are roundels depicting various common animals—pigs, monkeys, water buffaloes, roosters, and snakes. There are no mythological figures among the roundels, so one can reasonably conclude that these figures depict the animals that were commonly seen by the ancient Khmer people in the twelfth century. Notes Bibliography Laterite Laterite

SECTION 20

#1732859242189

1210-573: The Angkor monuments—which are widely distributed in Cambodia and Thailand—between the 9th and 13th centuries. The stone materials used were sandstone and laterite; brick had been used in monuments constructed in the 9th and 10th centuries. Two types of laterite can be identified; both types consist of the minerals kaolinite, quartz, hematite and goethite. Differences in the amounts of minor elements arsenic, antimony, vanadium and strontium were measured between

1265-564: The Elephants Terrace, behind the Prasat Suor Prat . ‘Khleang’ means ‘storeroom’ but it is unlikely that this was the function of the structures, A royal oath of allegiance is carved into the doorway of one Khleang indicating that they may have served as reception areas or even housing for visiting noblemen and ambassadors. The North Khleang was built in wood under Rajendravarman II and then rebuilt in stone by Jayavaraman V, probably before

1320-507: The Philippines. Laterites reflect past weathering conditions; 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. In India, laterite soils occupy an area of 240,000 square kilometres. Laterite soils have

1375-541: The Semi-Arid Tropics ( ICRISAT ) has employed this system to rehabilitate degraded laterite soils in Niger and increase smallholder farmers' incomes. In some places, these soils support grazing grounds and scrub forests. When moist, laterites can easily be cut with a spade into regular-sized blocks. Laterite is mined while it is below the water table, so it is wet and soft. Upon exposure to air it gradually hardens as

1430-510: The city are the former state temple of Baphuon , and Phimeanakas , which was incorporated into the Royal Palace. The Khmers did not draw any clear distinctions between Angkor Thom and Yashodharapura; even in the 14th century, an inscription used the earlier name. The name of Angkor Thom—great city—was in use from the 16th century. The last temple known to have been constructed in Angkor Thom

1485-489: The construction of the South Khleang. The Khleangs are unremarkable upon close inspection but picturesque from a distance, standing among the Prasat Suor Prat . This article about a building or structure in Cambodia is a stub . You can help Misplaced Pages by expanding it . Angkor Thom Angkor Thom ( Khmer : អង្គរធំ ) is the transform name from another alternative name of Nokor Thom ( Khmer : នគរធំ ), which

1540-418: The contrary, in the wetter parts of laterites subject to leaching ferricretes have been suggested to form. The mineralogical and chemical compositions of laterites are dependent on their parent rocks. Laterites consist mainly of quartz , zircon , and oxides of titanium , iron, tin , aluminum and manganese , which remain during the course of weathering. Quartz is the most abundant relic mineral from

1595-540: The earth which experienced prolonged tropical weathering of ultramafic rocks containing the ferro-magnesian minerals olivine , pyroxene , and amphibole . 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. Lateritic soils are

1650-527: The east road to the Victory Square and the Royal Palace north of the Bayon. It is around 30 minutes from central Siem Reap. The faces on the 23 m towers at the city gates, which are later additions to the main structure, take after those of the Bayon and pose the same problems of interpretation. They may represent the king himself, the bodhisattva Avalokiteshvara , guardians of the empire's cardinal points, or some combination of these. A causeway spans

1705-583: The effectiveness of granular laterite in removing phosphorus and heavy metals from landfill leachate . Initial laboratory studies show that laterite is capable of 99% removal of phosphorus from solution. A pilot-scale experimental facility containing laterite achieved 96% removal of phosphorus. This removal is greater than reported in other systems. Initial removals of aluminum and iron by pilot-scale facilities have been up to 85% and 98% respectively. Percolating columns of laterite removed enough cadmium , chromium and lead to undetectable concentrations. There

Khleangs - Misplaced Pages Continue

1760-659: The interior of Australia. Some of the oldest and most highly deformed ultramafic rocks which underwent laterization are found as petrified fossil soils in the complex Precambrian shields in Brazil and Australia. Smaller highly deformed Alpine-type intrusives have formed laterite profiles in Guatemala, Colombia, Central Europe, India and Burma. Large thrust sheets of Mesozoic island arcs and continental collision zones underwent laterization in New Caledonia, Cuba, Indonesian and

1815-450: 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 aluminum 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

1870-404: The lowest to highest water table levels—is progressively depleted of the easily leached ions of sodium , potassium , calcium and magnesium . A solution of these ions can have the correct pH to preferentially dissolve silicon oxide rather than the aluminum oxides and iron oxides . Silcrete has been suggested to form in zones in relatively dry "precipitating zones" of laterites. To

1925-495: The major source of early nickel. Rich laterite deposits in New Caledonia were mined starting the end of the 19th century to produce white metal . 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. About 70% of the Earth's land-based nickel resources are contained in laterites; they currently account for about 40% of

1980-466: The mid- Tertiary to the mid- Quaternary periods (35 to 1.5 million years ago). Statistical analyses show that the transition in the mean and variance levels of O during the middle of the Pleistocene was abrupt. 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

2035-472: The mid-1980s, constructed trial sections of bituminous-surfaced low-volume roads using laterite in place of stone as a base course. 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. In 1984 US$ 40,000 per 1 km (0.62 mi) was saved in Malawi by using laterite in this way. It

2090-509: The moat in front of each tower: these have a row of devas on the left and asuras on the right, each row holding a naga in the attitude of a tug-of-war. This appears to be a reference to the myth, popular in Angkor, of the Churning of the Sea of Milk . The temple-mountain of the Bayon, or perhaps the gate itself, would then be the pivot around which the churning takes place. The nagas may also represent

2145-517: 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, including T. R. Paton and M. A. J. Williams, specializing in regolith development have considered that hopeless confusion has evolved around the name. Material that looks highly similar to the Indian laterite occurs abundantly worldwide. Historically, laterite

2200-675: The moisture between the flat clay particles evaporates and the larger iron salts lock into a rigid lattice structure and become resistant to atmospheric conditions. The art of quarrying laterite material into masonry is suspected to have been introduced from the Indian subcontinent. They harden like iron when they are exposed to air. After 1000 CE Angkorian construction changed from circular or irregular earthen walls to rectangular temple enclosures of laterite, brick and stone structures. Geographic surveys show areas which have laterite stone alignments which may be foundations of temple sites that have not survived. The Khmer people constructed

2255-479: The more insoluble ions, predominantly iron and aluminum. The mechanism of leaching involves acid dissolving the host mineral lattice , followed by hydrolysis and precipitation of insoluble oxides and sulfates of iron, aluminum and silica under the high temperature conditions of a humid sub-tropical monsoon climate . An essential feature for the formation of laterite is the repetition of wet and dry seasons . Rocks are leached by percolating rain water during

Khleangs - Misplaced Pages Continue

2310-404: The ocean. It has the considerable water-holding capacity, depending on the depth of the formation. 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. The water table recedes slowly and is recharged several times during the rest of the year. In some high-density suburban areas

2365-409: The parent rock. Laterites vary significantly according to their location, climate and depth. The main host minerals for nickel and cobalt can be either iron oxides , clay minerals or manganese oxides . 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. Nickel laterites occur in zones of

2420-736: The rainwater 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. These soils are most suitable for plantation crops. They are good for oil palm, tea, coffee and cashew cultivation. The International Crops Research Institute for

2475-428: The temple contain laterite blocks behind the sandstone surface. The masonry was laid without joint mortar. It is used as a local building material in places such as Burkina Faso , where it is valued for being strong and for reducing heating and cooling costs. The French surfaced roads in the Cambodia, Thailand and Vietnam area with crushed laterite, stone or gravel. Kenya, during the mid-1970s, and Malawi, during

2530-528: The thick weathered layer and rarely exposed. Lateritic soils form the uppermost part of the laterite cover. In some places laterites contain pisolites and ferricrete , and they may be found in elevated positions as result of relief inversion . Cliff Ollier has criticized the usefulness of the concept given that it is used to mean different things to different authors. Reportedly some have used it for ferricrete, others for tropical red earth soil, and yet others for soil profiles made, from top to bottom, of

2585-497: The transition from the world of men to the world of the gods (the Bayon), or be guardian figures. The gateways themselves are 3.5 by 7 m, and would originally have been closed with wooden doors. The south gate is now by far the most often visited, as it is the main entrance to the city for tourists. At each corner of the city is a Prasat Chrung—corner shrine—built of sandstone and dedicated to Avalokiteshvara. These are cruciform with

2640-530: The two laterites. 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. It is a World Heritage site. 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. The foundations and internal parts of

2695-467: The various gods, goddesses, and other-worldly beings from the mythological stories and epic poems of Hinduism. Mingled with these images are actual known animals, like elephants, snakes, fish, and monkeys, in addition to dragon-like creatures that look like the stylized, elongated serpents (with feet and claws) found in Chinese art. But among the ruins of Ta Prohm , near a huge stone entrance, one can see that

2750-702: The water table could recede to 15 m (50 ft) below ground level during a prolonged dry period of more than 65 days. The Cabook Aquifer laterites support relatively shallow aquifers that are accessible to dug wells. In Northern Ireland, phosphorus enrichment of lakes due to agriculture is a significant problem. Locally available laterite—a low-grade bauxite rich in iron and aluminum—is used in acid solution, followed by precipitation to remove phosphorus and heavy metals at several sewage treatment facilities. Calcium-, iron- and aluminum-rich solid media are recommended for phosphorus removal. A study, using both laboratory tests and pilot-scale constructed wetlands, reports

2805-463: The wet season; the resulting solution containing the leached ions is brought to the surface by capillary action during the dry season. These ions form soluble salt compounds which dry on the surface; these salts are washed away during the next wet season. Laterite formation is favored in low topographical reliefs of gentle crests and plateaus which prevents erosion of the surface cover. The reaction zone where rocks are in contact with water—from

SECTION 50

#1732859242189

2860-555: Was Mangalartha , which was dedicated in 1295. Thereafter the existing structures continued to be modified from time to time, but any new creations were in perishable materials and have not survived. The Ayutthaya Kingdom , led by King Borommarachathirat II , sacked Angkor Thom, forcing the Khmers under Ponhea Yat to relocate their capital southeast to Phnom Penh . Angkor Thom was abandoned sometime prior to 1609, when an early western visitor wrote of an uninhabited city, "as fantastic as

2915-466: Was built under King Jayaviravarman and the southern (South Khleang) under his successor Suryavarman I —but they are of similar design (although South Khleang is slight narrower). They have given their name to the Khleang style, which is characterised by relatively simple lintels with a central kala . Other buildings in the style are Phimeanakas and Ta Keo . Rectangular sandstone buildings set opposite

2970-413: 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

3025-456: Was established as the capital of Jayavarman VII's empire and was the centre of his massive building program. One inscription found in the city refers to Jayavarman as the groom and the city as his bride. Angkor Thom seems not to be the first Khmer capital on the site, however. Yasodharapura , dating from three centuries earlier, was centred slightly further northwest, and Angkor Thom overlapped parts of it. The most notable earlier temples within

#188811