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102-537: Sioma is located on the west bank of the Zambezi River 130 kilometres (81 mi) north of Sesheke and 150 kilometres (93 mi) south of the provincial capital Mongu . The town is situated approximately 60 kilometres (37 mi) south of the town of Senanga which marks the southern extent of the Barotse Floodplain . Vegetation in the area is predominantly Dry Kalahari woodland. Annually,

204-591: A different impact on the ecosystems of the delta from today, as it brought nutrient-rich fresh water down to the Indian Ocean coastal wetlands. The lower Zambezi experienced a small flood surge early in the dry season as rain in the Gwembe catchment and north-eastern Zimbabwe rushed through while rain in the upper Zambezi, Kafue, and Lake Malawi basins, and Luangwa to a lesser extent, is held back by swamps and floodplains. The discharges of these systems contribute to

306-408: A distinctive composition or mode or origin. Special names still in wide use include amphibolite, greenschist , phyllite, marble, serpentinite , eclogite, migmatite , skarn , granulite , mylonite, and slate. The basic classification can be supplemented by terms describing mineral content or texture. For example, a metabasalt showing weak schistosity might be described as a gneissic metabasalt, and

408-455: A distinctive layering called foliation (derived from the Latin word folia , meaning "leaves"). Foliation develops when a rock is being shortened along one axis during recrystallization. This causes crystals of platy minerals, such as mica and chlorite , to become rotated such that their short axes are parallel to the direction of shortening. This results in a banded, or foliated, rock, with

510-416: A haven for migratory waterbirds, including pintails , garganey , African openbill ( Anastomus lamelligerus ), saddle-billed stork ( Ephippiorhynchus senegalensis ), wattled crane ( Bugeranus carunculatus ), and great white pelican ( Pelecanus onocrotalus ). Reptiles include Nile crocodile ( Crocodylus niloticus ), Nile monitor lizard ( Varanus niloticus ), African rock python ( Python sebae ),

612-469: A marble will not be identical with the amphibolite facies of a pelite. However, the facies are defined such that metamorphic rock with as broad a range of compositions as is practical can be assigned to a particular facies. The present definition of metamorphic facies is largely based on the work of the Finnish geologist, Pentti Eskola , with refinements based on subsequent experimental work. Eskola drew upon

714-533: A metamorphic rock to be classified in this manner, the protolith should be identifiable from the characteristics of the metamorphic rock itself, and not inferred from other information. Under the British Geological Survey's classification system, if all that can be determined about the protolith is its general type, such as sedimentary or volcanic, the classification is based on the mineral mode (the volume percentages of different minerals in

816-469: A much larger flood in March or April, with a mean monthly maximum for April of 6,700 m (240,000 cu ft) per second at the delta. The record flood was more than three times as big, 22,500 m (790,000 cu ft) per second being recorded in 1958. By contrast, the discharge at the end of the dry season averaged just 500 m (18,000 cu ft) per second. In the 1960s and 1970s,

918-413: A pelite containing abundant staurolite might be described as a staurolite pelite. [REDACTED] A metamorphic facies is a set of distinctive assemblages of minerals that are found in metamorphic rock that formed under a specific combination of pressure and temperature. The particular assemblage is somewhat dependent on the composition of that protolith, so that (for example) the amphibolite facies of

1020-519: A relatively mild grade of metamorphism, at temperatures of 350–500 °C (662–932 °F) and pressures of 200–500 MPa (2,000–5,000 bar). They can be divided into a lower group of metabasalts, including rare meta komatiites ; a middle group of meta-intermediate-rock and meta-felsic-rock; and an upper group of metasedimentary rock. The greenstone belts are surrounded by high-grade gneiss terrains showing highly deformed low-pressure, high-temperature (over 500 °C (932 °F)) metamorphism to

1122-549: A reputation as great cloth traders throughout the region. In a curious note, Goese-born Portuguese trader Manuel Caetano Pereira, who traveled to the Bisa homelands in 1796, was surprised to be shown a second, separate river referred to as the "Zambezi". This "other Zambezi" that puzzled Pereira is most likely what modern sources spell the Chambeshi River in northern Zambia. The Monomatapa notion (reported by Santos) that

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1224-410: A variety of metamorphic facies. Where subduction is taking place, the basalt of the subducting slab is metamorphosed to high-pressure metamorphic facies. It initially undergoes low-grade metamorphism to metabasalt of the zeolite and prehnite-pumpellyite facies , but as the basalt subducts to greater depths, it is metamorphosed to the blueschist facies and then the eclogite facies . Metamorphism to

1326-417: Is a great variety of metamorphic rock types. In general, if the protolith of a metamorphic rock can be determined, the rock is described by adding the prefix meta- to the protolith rock name. For example, if the protolith is known to be basalt , the rock will be described as a metabasalt. Likewise, a metamorphic rock whose protolith is known to be a conglomerate will be described as a metaconglomerate . For

1428-426: Is called a paired metamorphic belt . The main islands of Japan show three distinct paired metamorphic belts, corresponding to different episodes of subduction. Metamorphic rock is also exposed in metamorphic core complexes , which form in region of crustal extension. They are characterized by low-angle faulting that exposes domes of middle or lower crust metamorphic rock. These were first recognized and studied in

1530-515: Is dominated by metamorphic rock that has reached the amphibolite facies. Within the upper crust, which is the only part of the Earth's crust geologists can directly sample, metamorphic rock forms only from processes that can occur at shallow depth. These are contact (thermal) metamorphism , dynamic (cataclastic) metamorphism , hydrothermal metamorphism , and impact metamorphism . These processes are relatively local in occurrence and usually reach only

1632-476: Is formed as tectonic plates move apart. Hydrothermal metamorphism is extensive here. This is characterized by metasomatism by hot fluids circulating through the rock. This produces metamorphic rock of the greenschist facies. The metamorphic rock, serpentinite , is particularly characteristic of these settings, and represents chemical transformation of olivine and pyroxene in ultramafic rock to serpentine group minerals. Contact metamorphism takes place when magma

1734-403: Is injected into the surrounding solid rock ( country rock ). The changes that occur are greatest wherever the magma comes into contact with the rock because the temperatures are highest at this boundary and decrease with distance from it. Around the igneous rock that forms from the cooling magma is a metamorphosed zone called a contact aureole . Aureoles may show all degrees of metamorphism from

1836-534: Is joined by sizeable tributaries such as the Luena and the Chifumage flowing from highlands to the north-west. It turns south and develops a floodplain , with extreme width variation between the dry and rainy seasons. It enters dense evergreen Cryptosepalum dry forest , though on its western side, Western Zambezian grasslands also occur. Where it re-enters Zambia, it is nearly 400 m (1,300 ft) wide in

1938-405: Is known as burial metamorphism . This tends to produce low-grade metamorphic rock. Much more common is metamorphic rock formed during the collision process itself. The collision of plates causes high temperatures, pressures and deformation in the rocks along these belts. Metamorphic rock formed in these settings tends to shown well-developed schistosity. Metamorphic rock of orogenic belts shows

2040-601: Is lost through evaporation in its swamp systems. The 1940s and 1950s were particularly wet decades in the basin. Since 1975, it has been drier, the average discharge being only 70% of that for the years 1930 to 1958. Up to the Late Pliocene or Pleistocene (more than two million years ago), the upper Zambezi flowed south through what is now the Makgadikgadi Pan to the Limpopo River . The change of

2142-518: Is not included in the figures because it only occasionally overflows to any extent into the Zambezi. Because of the rainfall distribution, northern tributaries contribute much more water than southern ones; for example: The Northern Highlands catchment of the upper Zambezi contributes 25%, Kafue 8%, Luangwa and Shire Rivers 16% each, total 65% of Zambezi discharge. The large Cuando basin in the south-west, though, contributes only about 2 m /s because most

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2244-521: Is obstructed by a sand bar . A more northerly branch, called the Chinde mouth, has a minimum depth at low water of 2 metres (6 ft 7 in) at the entrance and 4 metres (13 ft) further in, and is the branch used for navigation. About 100 kilometres (62 mi) further north is a river called the Quelimane , after the town at its mouth. This stream, which is silting up, receives the overflow of

2346-481: Is sandy, and the banks are low and reed-fringed. At places, however, and especially in the rainy season, the streams unite into one broad, fast-flowing river. About 160 kilometres (99 mi) from the sea, the Zambezi receives the drainage of Lake Malawi through the Shire River . On approaching the Indian Ocean, the river splits up into a delta . Each of the primary distributaries, Kongone, Luabo, and Timbwe,

2448-506: Is sufficiently hard and dense that it is difficult to quarry. However, some quartzite is used as dimension stone , often as slabs for flooring, walls, or stairsteps. About 6% of crushed stone, used mostly for road aggregate, is quartzite. Marble is also prized for building construction and as a medium for sculpture. Schistose bedrock can pose a challenge for civil engineering because of its pronounced planes of weakness. A hazard may exist even in undisturbed terrain. On August 17, 1959,

2550-618: Is the fourth-longest river in Africa, the longest east-flowing river in Africa and the largest flowing into the Indian Ocean from Africa. Its drainage basin covers 1,390,000 km (540,000 sq mi), slightly less than half of the Nile 's. The 2,574 km (1,599 mi) river rises in Zambia and flows through eastern Angola , along the north-eastern border of Namibia and

2652-553: Is transformed physically or chemically at elevated temperature, without actually melting to any great degree. The importance of heating in the formation of metamorphic rock was first noted by the pioneering Scottish naturalist, James Hutton , who is often described as the father of modern geology. Hutton wrote in 1795 that some rock beds of the Scottish Highlands had originally been sedimentary rock but had been transformed by great heat. Hutton also speculated that pressure

2754-400: Is uncertain. Special classifications exist for metamorphic rocks with a volcaniclastic protolith or formed along a fault or through hydrothermal circulation . A few special names are used for rocks of unknown protolith but known modal composition, such as marble, eclogite , or amphibolite . Special names may also be applied more generally to rocks dominated by a single mineral, or with

2856-426: Is used only when very little else is known about the rock that would allow a more definite classification. Textural classifications may be prefixed to indicate a sedimentary protolith ( para- , such as paraschist) or igneous protolith ( ortho- , such as orthogneiss). When nothing is known about the protolith, the textural name is used without a prefix. For example, a schist is a rock with schistose texture whose protolith

2958-475: Is usually devoid of schistosity and forms a tough, equigranular rock. If the rock was originally banded or foliated (as, for example, a laminated sandstone or a foliated calc- schist ) this character may not be obliterated, and a banded hornfels is the product. Contact metamorphism close to the surface produces distinctive low-pressure metamorphic minerals, such as spinel , andalusite, vesuvianite , or wollastonite . Similar changes may be induced in shales by

3060-470: Is very low in silica) to metafelsic-rock (with a high silica content). Where the mineral mode cannot be determined, as is often the case when rock is first examined in the field , then classification must be based on texture. The textural types are: A hornfels is a granofels that is known to result from contact metamorphism. A slate is a fine-grained metamorphic rock that easily splits into thin plates but shows no obvious compositional layering. The term

3162-546: Is very uniform, dropping only by another 180 m (590 ft) across a distance of around 800 km (500 mi). The first of its large tributaries to enter the Zambezi is the Kabompo River in the North-Western Province of Zambia. The savanna through which the river flows gives way to a wide floodplain, studded with Borassus fan palms . A little farther south is the confluence with

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3264-570: The Basin and Range Province of southwestern North America, but are also found in southern Aegean Sea , in the D'Entrecasteaux Islands , and in other areas of extension. Continental shields are regions of exposed ancient rock that make up the stable cores of continents. The rock exposed in the oldest regions of shields, which is of Archean age (over 2500 million years old), mostly belong to granite-greenstone belts. The greenstone belts contain metavolcanic and metasedimentary rock that has undergone

3366-545: The Ikelenge District of North-Western Province , Zambia, at about 1,524 metres (5,000 ft) above sea level . The area around the source is a national monument, forest reserve, and important bird area . Eastward of the source, the watershed between the Congo and Zambezi Basins is a well-marked belt of high ground, running nearly east–west and falling abruptly to the north and south. This distinctly cuts off

3468-736: The Itezhi-Tezhi Dam 's deleterious effects on the Kafue Flats, this has these effects: The Zambezi Delta has extensive seasonally and permanently flooded grasslands, savannas, and swamp forests. Together with the floodplains of the Buzi , Pungwe , and Save Rivers, the Zambezi's floodplains make up the World Wildlife Fund 's Zambezian coastal flooded savanna ecoregion in Mozambique. The flooded savannas lie close to

3570-579: The Kuomboka . After Lealui, the river turns south-southeast. From the east, it continues to receive numerous small streams, but on the west, it is without major tributaries for 240 km. Before this, the Ngonye Falls and subsequent rapids interrupt navigation. South of Ngonye Falls, the river briefly borders Namibia's Caprivi Strip . Below the junction of the Cuando River and the Zambezi,

3672-542: The Lungwebungu River . This is the beginning of the Barotse Floodplain , the most notable feature of the upper Zambezi, but this northern part does not flood so much and includes islands of higher land in the middle. About 30 km below the confluence of the Lungwebungu, the country becomes very flat, and the typical Barotse Floodplain landscape unfolds, with the flood reaching a width of 25 km in

3774-528: The Quelimane or Quá-Qua, a small river on the northern end of the delta, which at that time was connected by navigable channels to the Zambezi River proper (the connection silted up by the 1830s). In a few of the oldest maps, the entire river is denoted as such. By the 16th century, a new name emerged, the Cuama River (sometimes "Quama" or "Zuama"). Cuama was the local name given by the dwellers of

3876-679: The Swahili coast for an outpost located on one of the southerly islands of the delta (near the Luabo channel). Most old nautical maps denote the Luabo entry as Cuama, the entire delta as the "rivers of Cuama", and the Zambezi proper as the "Cuama River". In 1552, Portuguese chronicler João de Barros noted that the same Cuama River was called Zembere by the inland people of Monomatapa . The Portuguese Dominican friar João dos Santos , visiting Monomatapa in 1597 reported it as Zambeze (Bantu languages frequently shifts between z and r) and inquired into

3978-450: The atoms and ions in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact. Metamorphic rocks are characterized by their distinctive mineral composition and texture. Because every mineral is stable only within certain limits, the presence of certain minerals in metamorphic rocks indicates the approximate temperatures and pressures at which

4080-402: The crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process. Metamorphic rocks are typically more coarsely crystalline than the protolith from which they formed. Atoms in the interior of a crystal are surrounded by a stable arrangement of neighboring atoms. This is partially missing at the surface of

4182-515: The "Espirito Santo" Rivers converging deep in the interior, at the same lake. However, the Bisa-derived etymology is not without dispute. In 1845, W.D. Cooley, examining Pereira's notes, concluded the term "Zambezi" derives not from the Bisa people, but rather from the Bantu term "mbege"/"mbeze" ("fish"), and consequently it probably means merely "river of fish". David Livingstone , who reached

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4284-506: The Batoka Gorge, the current being continually interrupted by reefs. It has been described as one of the world's most spectacular whitewater trips, a tremendous challenge for kayakers and rafters alike. Beyond the gorge are a succession of rapids that end 240 km (150 mi) below Victoria Falls. Over this distance, the river drops 250 m (820 ft). At this point, the river enters Lake Kariba , created in 1959 following

4386-456: The Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust. Some examples of metamorphic rocks are gneiss , slate , marble , schist , and quartzite . Slate and quartzite tiles are used in building construction. Marble is also prized for building construction and as a medium for sculpture. On

4488-435: The Earth's surface, where they are subject to high temperatures and the great pressure of the rock layers above. They can also form from tectonic processes such as continental collisions, which cause horizontal pressure, friction, and distortion. Metamorphic rock can be formed locally when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior. The study of metamorphic rocks (now exposed at

4590-455: The Indian Ocean coast. Mangroves fringe the delta's shoreline. Although the dams have stemmed some of the annual flooding of the lower Zambezi and caused the area of floodplain to be greatly reduced, they have not removed flooding completely. They cannot control extreme floods, and they have only made medium-level floods less frequent. When heavy rain in the lower Zambezi combines with significant runoff upstream, massive floods still happen, and

4692-538: The Indian Ocean is navigable, although the river is shallow in many places during the dry season. This shallowness arises as the river enters a broad valley and spreads out over a large area. Only at one point, the Lupata Gorge , 320 kilometres (200 mi) from its mouth, is the river confined between high hills. Here, it is scarcely 200 metres (660 ft) wide. Elsewhere it is from 5 to 8 kilometres (3 to 5 mi) wide, flowing gently in many streams. The river bed

4794-592: The Swahili (and later Portuguese) upriver trade station at Sena . In 1752, the Zambezi Delta, under the name "Rivers of Sena" ( Rios de Sena ) formed a colonial administrative district of Portuguese Mozambique , but common usage of "Zambezi" led eventually to a royal decree in 1858 officially renaming the district " Zambézia ". The Zambezi region was known to medieval geographers as the Empire of Monomotapa , and

4896-471: The Zambezi in the rainy season. Average, minimum and maximum discharge of the Zambezi River at Marromeu (Lower Zambezi). Period from 1998 to 2022. The delta of the Zambezi is today about half as broad as it was before the construction of the Kariba and Cahora Bassa dams controlled the seasonal variations in the flow rate of the river. Before the dams were built, seasonal flooding of the Zambezi had quite

4998-543: The Zambezi was sourced from a great internal lake might be a reference to one of the African Great Lakes . One of the names reported by early explorers for Lake Malawi was "Lake Zambre" (probably a corruption of "Zambezi"), possibly because Lake Malawi is connected to the lower Zambezi via the Shire River. The Monomatapa story resonated with the old European notion, drawn from classical antiquity, that all

5100-482: The amphibolite or granulite facies. These form most of the exposed rock in Archean cratons. The granite-greenstone belts are intruded by a distinctive group of granitic rocks called the tonalite - trondhjemite - granodiorite or TTG suite. These are the most voluminous rocks in the craton and may represent an important early phase in the formation of continental crust. Mid-ocean ridges are where new oceanic crust

5202-404: The bands showing the colors of the minerals that formed them. Foliated rock often develops planes of cleavage . Slate is an example of a foliated metamorphic rock, originating from shale , and it typically shows well-developed cleavage that allows slate to be split into thin plates. The type of foliation that develops depends on the metamorphic grade. For instance, starting with a mudstone ,

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5304-536: The basin of the Lualaba (the main branch of the upper Congo) from the Zambezi. In the neighborhood of the source, the watershed is not as clearly defined, but the two river systems do not connect. The region drained by the Zambezi is a vast, broken-edged plateau 900–1,200 m high, composed in the remote interior of metamorphic beds and fringed with the igneous rocks of the Victoria Falls. At Chupanga , on

5406-406: The building of dams changed that pattern completely. Downstream, the mean monthly minimum–maximum was 500 to 6,000 m (18,000 to 212,000 cu ft) per second; now it is 1,000 to 3,900 m (35,000 to 138,000 cu ft) per second. Medium-level floods especially, of the kind to which the ecology of the lower Zambezi was adapted, happen less often and have a shorter duration. As with

5508-420: The bulk composition of a rock. Hot fluids circulating through pore space in the rock can dissolve existing minerals and precipitate new minerals. Dissolved substances are transported out of the rock by the fluids while new substances are brought in by fresh fluids. This can obviously change the mineral makeup of the rock. However, changes in the mineral composition can take place even when the bulk composition of

5610-399: The burning of coal seams. This produces a rock type named clinker . There is also a tendency for metasomatism between the igneous magma and sedimentary country rock, whereby the chemicals in each are exchanged or introduced into the other. In that case, hybrid rocks called skarn arise. Dynamic (cataclastic) metamorphism takes place locally along faults . Here intense shearing of

5712-445: The calm stretches of the river, as well as Nile crocodiles. Monitor lizards are found in many places. Birds are abundant, with species including heron , pelican , egret , lesser flamingo , and African fish eagle present in large numbers. Riverine woodland also supports many large animals, such as buffalo, zebras , giraffes , and elephants . The Zambezi also supports several hundred species of fish, some of which are endemic to

5814-435: The circulation of fluids through buried rock, to the list of processes that help bring about metamorphism. However, metamorphism can take place without metasomatism ( isochemical metamorphism ) or at depths of just a few hundred meters where pressures are relatively low (for example, in contact metamorphism ). Metamorphic processes change the texture or mineral composition of the metamorphosed rock. Metasomatism can change

5916-427: The collision of tectonic plates at convergent boundaries . Here formerly deeply buried rock has been brought to the surface by uplift and erosion. The metamorphic rock exposed in orogenic belts may have been metamorphosed simply by being at great depths below the Earth's surface, subjected to high temperatures and the great pressure caused by the immense weight of the rock layers above. This kind of regional metamorphism

6018-468: The completion of the Kariba Dam . The lake is one of the largest man-made lakes in the world, and the hydroelectric power-generating facilities at the dam provide electricity to much of Zambia and Zimbabwe. The Luangwa and Kafue rivers are the two largest left-hand tributaries of the Zambezi. The Kafue joins the main river in a quiet, deep stream about 180 m (590 ft) wide. From this point,

6120-725: The confluence with the Luanginga is Lealui , one of the capitals of the Lozi people , who populate the Zambian region of Barotseland in the Western Province. The chief of the Lozi maintains one of his two compounds at Lealui; the other is at Limulunga , which is on high ground and serves as the capital during the rainy season. The annual move from Lealui to Limulunga is a major event, celebrated as one of Zambia's best-known festivals,

6222-491: The contact area to unmetamorphosed (unchanged) country rock some distance away. The formation of important ore minerals may occur by the process of metasomatism at or near the contact zone. Contact aureoles around large plutons may be as much as several kilometers wide. The term hornfels is often used by geologists to signify those fine grained, compact, non-foliated products of contact metamorphism. The contact aureole typically shows little deformation, and so hornfels

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6324-591: The course of the river, as well as the position of lakes Ngami and Nyasa , were generally accurate in early maps. These were probably constructed from Arab information. Metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism . The original rock ( protolith ) is subjected to temperatures greater than 150 to 200 °C (300 to 400 °F) and, often, elevated pressure of 100 megapascals (1,000  bar ) or more, causing profound physical or chemical changes. During this process,

6426-612: The crystal, producing a surface energy that makes the surface thermodynamically unstable. Recrystallization to coarser crystals reduces the surface area and so minimizes the surface energy. Although grain coarsening is a common result of metamorphism, rock that is intensely deformed may eliminate strain energy by recrystallizing as a fine-grained rock called mylonite . Certain kinds of rock, such as those rich in quartz, carbonate minerals , or olivine, are particularly prone to form mylonites, while feldspar and garnet are resistant to mylonitization. Many kinds of metamorphic rocks show

6528-423: The eclogite facies releases a great deal of water vapor from the rock, which drives volcanism in the overlying volcanic arc . Eclogite is also significantly denser than blueschist, which drives further subduction of the slab deep into the Earth's mantle . Metabasalt and blueschist may be preserved in blueschist metamorphic belts formed by collisions between continents. They may also be preserved by obduction onto

6630-442: The endemic Pungwe worm snake ( Leptotyphlops pungwensis ), and three other snakes that are nearly endemic - floodplain water snake ( Lycodonomorphus whytei obscuriventris ), dwarf wolf snake ( Lycophidion nanus ), and swamp viper ( Proatheris ). Several butterfly species are endemic. The north of the Zambezi basin has mean annual rainfall of 1100 to 1400 mm, which declines towards the south, reaching about half that figure in

6732-437: The following sequence develops with increasing temperature: The mudstone is first converted to slate, which is a very fine-grained, foliated metamorphic rock, characteristic of very low grade metamorphism. Slate in turn is converted to phyllite , which is fine-grained and found in areas of low grade metamorphism. Schist is medium to coarse-grained and found in areas of medium grade metamorphism. High-grade metamorphism transforms

6834-751: The great African rivers—the Nile, the Senegal , the Congo, and the Zambezi—were all sourced from the same great internal lake. The Portuguese were also told that the Mozambican Espirito Santo "river" (actually an estuary formed by the Umbeluzi , Matola , and Tembe Rivers) was sourced from a lake (hence its outlet became known as Delagoa Bay ). As a result, several old maps depict the Zambezi and

6936-449: The identical composition, Al 2 SiO 5 . Likewise, forsterite is stable over a broad range of pressure and temperature in marble , but is converted to pyroxene at elevated pressure and temperature in more silicate-rich rock containing plagioclase , with which the forsterite reacts chemically. Many complex high-temperature reactions may take place between minerals without them melting, and each mineral assemblage produced indicates

7038-437: The low-pressure facies, such as the hornfels and sanidinite facies . Most metamorphic rock is formed by regional metamorphism in the middle and lower crust, where the rock reaches the higher-pressure metamorphic facies. This rock is found at the surface only where extensive uplift and erosion has exhumed rock that was formerly much deeper in the crust. Metamorphic rock is extensively exposed in orogenic belts produced by

7140-440: The lower Zambezi, thin strata of grey and yellow sandstones , with an occasional band of limestone , crop out on the bed of the river in the dry season, and these persist beyond Tete , where they are associated with extensive seams of coal. Coal is also found in the district just below Victoria Falls. Gold-bearing rocks occur in several places. The river flows to the southwest into Angola for about 240 km (150 mi), then

7242-459: The native idea of this magnificent stream being the main drain of the country". Other historical records show that the river was called Kasambabezi by the Tonga people, which means “only those who know the river can bath in it.” a name which is still in use to this day. In Portuguese records, the "Cuama River" term disappeared and gave way to the term "Sena River" ( Rio de Sena ), a reference to

7344-473: The northern border of Botswana , then along the border between Zambia and Zimbabwe to Mozambique , where it crosses the country to empty into the Indian Ocean. The Zambezi's most noted feature is Victoria Falls . Its other falls include the Chavuma Falls at the border between Zambia and Angola, and Ngonye Falls near Sioma in western Zambia. The two main sources of hydroelectric power on

7446-547: The northward bend of the Zambezi is checked, and the stream continues due east. At the confluence of the Luangwa (15°37' S), it enters Mozambique. The middle Zambezi ends where the river enters Lake Cahora Bassa , formerly the site of dangerous rapids known as Kebrabassa; the lake was created in 1974 by the construction of the Cahora Bassa Dam. The lower Zambezi's 650 kilometres (400 mi) from Cahora Bassa to

7548-576: The origins of the name; he was told it was named after a people. "The River Cuama is by them called Zambeze; the head whereof is so farre within Land that none of them know it, but by tradition of their Progenitors say it comes from a Lake in the midst of the continent which yeelds also other great Rivers, divers ways visiting the Sea. They call it Zambeze, of a Nation of Cafres dwelling neere that Lake which are so called." —J. Santos Ethiopia Oriental , 1609 Thus,

7650-453: The other hand, schist bedrock can pose a challenge for civil engineering because of its pronounced planes of weakness. Metamorphic rocks form one of the three great divisions of rock types. They are distinguished from igneous rocks , which form from molten magma , and sedimentary rocks , which form from sediments eroded from existing rock or precipitated chemically from bodies of water. Metamorphic rocks are formed when existing rock

7752-460: The overriding plate as part of ophiolites . Eclogites are occasionally found at sites of continental collision, where the subducted rock is rapidly brought back to the surface, before it can be converted to the granulite facies in the hot upper mantle. Many samples of eclogite are xenoliths brought to the surface by volcanic activity. Many orogenic belts contain higher-temperature, lower-pressure metamorphic belts. These may form through heating of

7854-468: The rainy season and flows rapidly, with rapids ending in the Chavuma Falls , where the river flows through a rocky fissure. The river drops about 400 m (1,300 ft) in elevation from its source at 1,500 m (4,900 ft) to the Chavuma Falls at 1,100 m (3,600 ft), over a distance of about 400 km (250 mi). From this point to the Victoria Falls, the level of the basin

7956-549: The rainy season. For more than 200 km downstream, the annual flood cycle dominates the natural environment and human life, society, and culture. About 80 km further down, the Luanginga , which with its tributaries drains a large area to the west, joins the Zambezi. A short distance higher up on the east, the main stream is joined in the rainy season by overflow of the Luampa / Luena system. A short distance downstream of

8058-708: The river are the Kariba Dam , which provides power to Zambia and Zimbabwe, and the Cahora Bassa Dam in Mozambique, which provides power to Mozambique and South Africa . Additionally, two smaller power stations are along the Zambezi River in Zambia, one at Victoria Falls and the other in Zengamina , near Kalene Hill in the Ikelenge District . The river rises in a black, marshy dambo in dense, undulating miombo woodland 50 km (31 mi) north of Mwinilunga and 20 km (12 mi) south of Ikelenge in

8160-577: The river bends almost due east. Here, the river is broad and shallow and flows slowly, but as it flows eastward towards the border of the great central plateau of Africa, it reaches a chasm into which the Victoria Falls plunge. The Victoria Falls are considered the boundary between the upper and middle Zambezi. Below them, the river continues to flow due east for about 200 km (120 mi), cutting through perpendicular walls of basalt 20 to 60 m (66 to 197 ft) apart in hills 200 to 250 m (660 to 820 ft) high. The river flows swiftly through

8262-489: The river course is the result of epeirogenic movements that lifted up the surface at the present-day water divide between both rivers. Meanwhile, 1,000 km (620 mi) east, a western tributary of the Shire River in the East African Rift 's southern extension through Malawi eroded a deep valley on its western escarpment. At a slow rate, the middle Zambezi started cutting back the bed of its river towards

8364-743: The river. Important species include cichlids , which are fished heavily for food, as well as catfish, tigerfish, yellowfish , and other large species. The bull shark is sometimes known as the Zambezi shark after the river, not to be mistaken with Glyphis freshwater shark genus that inhabit the river, as well. Upper Zambezi: 507,200 km , discharges 1044 m /s at Victoria Falls, comprising: Middle Zambezi cumulatively 1,050,000 km , 2442 m /s, measured at Cahora Bassa Gorge Lower Zambezi cumulatively, 1,378,000 km , 3424 m /s, measured at Marromeu Total Zambezi river basin : 1,390,000 km , 3424 m /s discharged into delta Source: Beilfuss & Dos Santos (2001) The Okavango Basin

8466-475: The rock by ascending magmas of volcanic arcs, but on a regional scale. Deformation and crustal thickening in an orogenic belt may also produce these kinds of metamorphic rocks. These rocks reach the greenschist , amphibolite, or granulite facies and are the most common of metamorphic rocks produced by regional metamorphosis. The association of an outer high-pressure, low-temperature metamorphic zone with an inner zone of low-pressure, high-temperature metamorphic rocks

8568-421: The rock does not change. This is possible because all minerals are stable only within certain limits of temperature, pressure, and chemical environment. For example, at atmospheric pressure, the mineral kyanite transforms to andalusite at a temperature of about 190 °C (374 °F). Andalusite, in turn, transforms to sillimanite when the temperature reaches about 800 °C (1,470 °F). All three have

8670-458: The rock remains mostly in the solid state, but gradually recrystallizes to a new texture or mineral composition. The protolith may be an igneous , sedimentary , or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by their protolith, their chemical and mineral makeup, and their texture . They may be formed simply by being deeply buried beneath

8772-423: The rock to gneiss , which is coarse to very coarse-grained. Rocks that were subjected to uniform pressure from all sides, or those that lack minerals with distinctive growth habits, will not be foliated. Marble lacks platy minerals and is generally not foliated, which allows its use as a material for sculpture and architecture. Metamorphic rocks are one of the three great divisions of all rock types, and so there

8874-495: The rock typically forms mylonites. Impact metamorphism is unlike other forms of metamorphism in that it takes place during impact events by extraterrestrial bodies. It produces rare ultrahigh pressure metamorphic minerals, such as coesite and stishovite . Coesite is rarely found in eclogite brought to the surface in kimberlite pipes , but the presence of stishovite is unique to impact structures. Slate tiles are used in construction, particularly as roof shingle. Quartzite

8976-407: The rock underwent metamorphism. These minerals are known as index minerals . Examples include sillimanite , kyanite , staurolite , andalusite , and some garnet . Other minerals, such as olivines , pyroxenes , hornblende , micas , feldspars , and quartz , may be found in metamorphic rocks but are not necessarily the result of the process of metamorphism. These minerals can also form during

9078-486: The rock). Metasedimentary rocks are divided into carbonate-rich rock (metacarbonates or calcsilicate-rocks) or carbonate-poor rocks, and the latter are further classified by the relative abundance of mica in their composition. This ranges from low-mica psammite through semipelite to high-mica pelite . Psammites composed mostly of quartz are classified as quartzite. Metaigneous rocks are classified similarly to igneous rocks, by silica content, from meta-ultramafic-rock (which

9180-406: The sedimentary rock limestone and chalk change into larger crystals in the metamorphic rock marble . In metamorphosed sandstone, recrystallization of the original quartz sand grains results in very compact quartzite, also known as metaquartzite, in which the often larger quartz crystals are interlocked. Both high temperatures and pressures contribute to recrystallization. High temperatures allow

9282-747: The settlement as a hamlet. Pinto also described how the Lui government forced local residents to act as porters for canoes attempting to get around the nearby Ngonye Falls . Expansion of the town started in 1957 when the catholic Irish Capuchin Franciscans established the Saint Anthony mission station on the Zambezi river at the town. In 2012 the town was made the capital of the newly created Sioma District . Zambezi River (Period: 1971–2000)4,256.1 m /s (150,300 cu ft/s) The Zambezi (also spelled Zambeze and Zambesi )

9384-517: The south-west. The rain falls in a 4-to-6-month summer rainy season when the Intertropical Convergence Zone moves over the basin from the north between October and March. Evaporation rates are high (1600 mm-2300 mm), and much water is lost this way in swamps and floodplains, especially in the south-west of the basin. The river supports large populations of many animals. Hippopotamuses are abundant along most of

9486-404: The temperatures and pressures at the time of metamorphism. These reactions are possible because of rapid diffusion of atoms at elevated temperature. Pore fluid between mineral grains can be an important medium through which atoms are exchanged. The change in the particle size of the rock during the process of metamorphism is called recrystallization . For instance, the small calcite crystals in

9588-514: The term "Zambezi" is after a people who live by a great lake to the north. The most likely candidates are the "M'biza", or Bisa people (in older texts given as Muisa, Movisa, Abisa, Ambios, and other variations), a Bantu people who live in what is now central-eastern Zambia, between the Zambezi River and Lake Bangweolo (at the time, before the Lunda invasion, the Bisa would have likely stretched further north, possibly to Lake Tanganyika ). The Bisa had

9690-510: The town gets an average of 737 millimetres (29.0 in) of rain. An Early Iron Age site was excavated at Sioma which has been dated to the mid centuries of the first millennium. Some of the pottery at the site resembles that which is found in Nqoma, Angola. In the 1880s the Portuguese explorer Alexandre Alberto da Rocha de Serpa Pinto and American James Dabney McCabe both described

9792-458: The upper Zambezi in 1853, refers to it as "Zambesi", but also makes note of the local name "Leeambye" used by the Lozi people , which he says means "large river or river par excellence". Livingstone records other names for the Zambezi—Luambeji, Luambesi, Ambezi, Ojimbesi, and Zambesi—applied by different peoples along its course, and asserts they "all possess a similar signification and express

9894-451: The use of granulite as a classification for rock metamorphosed to the granulite facies. Instead, such rock will often be classified as a granofels. However, this approach is not universally accepted. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. The lower continental crust is mostly metamafic-rock and pelite which have reached the granulite facies . The middle continental crust

9996-399: The west, aided by grabens ( rift valleys ) forming along its course in an east–west axis. As it did so, it captured several south-flowing rivers such as the Luangwa and Kafue. Eventually, the large lake trapped at Makgadikgadi (or a tributary of it) was captured by the middle Zambezi cutting back towards it, and emptied eastwards. The upper Zambezi was captured, as well. The middle Zambezi

10098-644: The wetlands are still an important habitat. The shrinking of the wetlands, though, resulted in uncontrolled hunting of animals such as buffalo and waterbuck during the Mozambican Civil War . Although the region has had a reduction in the populations of the large mammals, it is still home to some, including the reedbuck and migrating eland . Carnivores found here include lion ( Panthera leo ), leopard ( Panthera pardus ), cheetah ( Acinonyx jubatus ), spotted hyena ( Crocuta crocuta ), and side-striped jackal ( Canis adustus ). The floodplains are

10200-566: The zonal schemes, based on index minerals, that were pioneered by the British geologist, George Barrow . The metamorphic facies is not usually considered when classifying metamorphic rock based on protolith, mineral mode, or texture. However, a few metamorphic facies produce rock of such distinctive character that the facies name is used for the rock when more precise classification is not possible. The chief examples are amphibolite and eclogite . The British Geological Survey strongly discourages

10302-487: Was about 300 m (980 ft) lower than the upper Zambezi, and a high waterfall formed at the edge of the basalt plateau across which the upper river flows. This was the first Victoria Falls, somewhere down the Batoka Gorge near where Lake Kariba is now. The first European to come across the Zambezi River was Vasco da Gama in January 1498, who anchored at what he called Rio dos Bons Sinais (River of Good Omens), now

10404-419: Was important in metamorphism. This hypothesis was tested by his friend, James Hall , who sealed chalk into a makeshift pressure vessel constructed from a cannon barrel and heated it in an iron foundry furnace. Hall found that this produced a material strongly resembling marble , rather than the usual quicklime produced by heating of chalk in the open air. French geologists subsequently added metasomatism ,

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