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49-481: The Turpan Depression or Turfan Depression , is a fault -bounded trough located around and south of the city- oasis of Turpan , in the Xinjiang Autonomous Region in far Western China , about 150 kilometres (93 mi) southeast of the regional capital Ürümqi . It includes Lake Ayding , −154 metres (−505 ft), the second or third lowest depression on Earth . By some measures, it

98-405: A decollement . Extensional decollements can grow to great dimensions and form detachment faults , which are low-angle normal faults with regional tectonic significance. Due to the curvature of the fault plane, the horizontal extensional displacement on a listric fault implies a geometric "gap" between the hanging and footwalls of the fault forms when the slip motion occurs. To accommodate into

147-860: A plate boundary. This class is related to an offset in a spreading center , such as a mid-ocean ridge , or, less common, within continental lithosphere , such as the Dead Sea Transform in the Middle East or the Alpine Fault in New Zealand. Transform faults are also referred to as "conservative" plate boundaries since the lithosphere is neither created nor destroyed. Dip-slip faults can be either normal (" extensional ") or reverse . The terminology of "normal" and "reverse" comes from coal mining in England, where normal faults are

196-582: A fault hosting valuable porphyry copper deposits is northern Chile's Domeyko Fault with deposits at Chuquicamata , Collahuasi , El Abra , El Salvador , La Escondida and Potrerillos . Further south in Chile Los Bronces and El Teniente porphyry copper deposit lie each at the intersection of two fault systems. Faults may not always act as conduits to surface. It has been proposed that deep-seated "misoriented" faults may instead be zones where magmas forming porphyry copper stagnate achieving

245-500: A fault is locked, and when it reaches a level that exceeds the strength threshold, the fault ruptures and the accumulated strain energy is released in part as seismic waves , forming an earthquake . Strain occurs accumulatively or instantaneously, depending on the liquid state of the rock; the ductile lower crust and mantle accumulate deformation gradually via shearing , whereas the brittle upper crust reacts by fracture – instantaneous stress release – resulting in motion along

294-410: A fault often forms a discontinuity that may have a large influence on the mechanical behavior (strength, deformation, etc.) of soil and rock masses in, for example, tunnel , foundation , or slope construction. The level of a fault's activity can be critical for (1) locating buildings, tanks, and pipelines and (2) assessing the seismic shaking and tsunami hazard to infrastructure and people in

343-408: A fault's age by studying soil features seen in shallow excavations and geomorphology seen in aerial photographs. Subsurface clues include shears and their relationships to carbonate nodules , eroded clay, and iron oxide mineralization, in the case of older soil, and lack of such signs in the case of younger soil. Radiocarbon dating of organic material buried next to or over a fault shear

392-599: A harsh, continental desert climate (Koppen BWk ) in which the precipitation is far less than the potential evaporation. At Turpan City, July is the hottest month with a 24-hour average temperature of 32.2 °C (90.0 °F) and January the coldest with a 24-hour average temperature of −7.6 °C (18.3 °F). Monthly rainfall is highest in June, at 2.9 millimetres (0.11 in) and lowest in February and April, at 0.5 mm (0.020 in). The annual average precipitation

441-481: A result of rock-mass movements. Large faults within Earth 's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults . Energy release associated with rapid movement on active faults is the cause of most earthquakes . Faults may also displace slowly, by aseismic creep . A fault plane

490-447: A salt mill, which uses the region's alum salt crystals and saltpeter raw materials to manufacture chemical products. Scenic tours also run near the lake. On 24 July 2015, a new China-wide high temperature record was set at a meteorological station near Aydingkol, with a temperature of 50.3 °C (122.5 °F), a record it held until 17 July 2023 when Sanbao hit 52.2 °C (126 °F). This Xinjiang location article

539-694: Is also the hottest and driest area in China during the summer. The Turpan Basin is a fault-bounded trough located in the eastern part of the Tian Shan . It covers an area of 50,000 square kilometres (19,000 sq mi). The surrounding mountain ranges are: the central Tian Shan in the west, the Bogda Shan in the north-west, the Haerlike Shan in the north-west, and the Jueluotage Shan in

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588-651: Is located near Turpan. Also in the center of the basin lies the Ayding Lake (Moonlight Lake) which has an elevation of 154.5 m (507 ft) below sea level, the sixth lowest exposed elevation on the Earth's land surface . It is the lowest surface point in China. The Shihongtan uranium ore deposit is located at the southwestern margin of the Turpan Depression, some 35 km (22 mi) south-southwest from Turpan City. The ancient city of Gaochang

637-543: Is often critical in distinguishing active from inactive faults. From such relationships, paleoseismologists can estimate the sizes of past earthquakes over the past several hundred years, and develop rough projections of future fault activity. Many ore deposits lie on or are associated with faults. This is because the fractured rock associated with fault zones allow for magma ascent or the circulation of mineral-bearing fluids. Intersections of near-vertical faults are often locations of significant ore deposits. An example of

686-511: Is only 15.7 mm (0.62 in), falling on only 13 days per year. In contrast to this, the potential annual evaporation rate reaches 3,000 mm (120 in). Because of its climate, the area is sometimes counted as one of the Furnaces of China , although the locations included under this heading vary. On the shores of Aydingkol Lake , reeds, tamarisks , saxauls , as well as other shrubs and weeds can be found. Away from sources of water,

735-424: Is the lowest point in China . This lake is now totally dried, and very muddy and salty. In ancient times, Ayding Lake was known as juéluòwǎn (觉洛浣). The Uyghur derived name Aydingköl means "moon lake", due to the lake having a layer of white salt along its edge, giving the appearance of a shining moon. The lake is located in the south hinterland of the Turpan Depression, approximately 35 kilometres away from

784-444: Is the plane that represents the fracture surface of a fault. A fault trace or fault line is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A fault zone is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur

833-463: The Chesapeake Bay impact crater . Ring faults are the result of a series of overlapping normal faults, forming a circular outline. Fractures created by ring faults may be filled by ring dikes . Synthetic and antithetic are terms used to describe minor faults associated with a major fault. Synthetic faults dip in the same direction as the major fault while the antithetic faults dip in

882-709: The 77 known caves. The desert climate has favored preservation of the content of the Astana-Karakhoja ancient tombs , which are located about 6 km from the ancient city of Gaochang. The tombs are the burial place for nobles, officials, and others who were interred there from the times of the Western Jin dynasty until the middle of the Tang dynasty era. The modern city of Turpan has a population of 242,000, of whom 71% are Uyghur . The city relies on wells and traditional karez for water. The Turpan Basin has

931-534: The Turpan Basin is not covered by vegetation. Consequently, agriculture is limited to oasis and depends on a sophisticated irrigation system known as the Karez System . The irrigation water comes from the surrounding mountain ranges, in particular from the annual melting of the snow. The Karez System consists of wells, underground channels, ground canals, and small reservoirs, which use the natural slope of

980-648: The area of the Turpan Depression proper as 28,600 km (11,000 sq mi), that of the Hami Depression as 19,300 km (7,500 sq mi), and for the entire Turpan-Hami Basin, as 48,000 km (19,000 sq mi). The Turpan Basin formed in a shear zone during the Late Permian due to motion between the East European and the Angaran craton . It was subsequently deformed by

1029-472: The city of Turpan . From east to west, the lake spans 40 kilometres; the north-south span is 8 kilometres; and the total area of the lake is 200 square kilometres. The lake was formed from the formation of an orogeny of the Himalayas 249 million years ago, and once held approximately 5 million square kilometres of inland sea, which at one time surged up and became vastly extended. During the winter of 1948,

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1078-590: The collision of the Indian Plate and Eurasian Plate in the Cenozoic . In the latter deformation, a thrust fault belt running from east to west, the Flaming Mountains , was formed in the center of the basin. The Flaming Mountains are 98 km (61 mi) long and 9 km (5.6 mi) wide; the highest peak reaches an elevation of 831.7 m (2,729 ft) above sea level. The Turfan volcano

1127-414: The crust. A thrust fault has the same sense of motion as a reverse fault, but with the dip of the fault plane at less than 45°. Thrust faults typically form ramps, flats and fault-bend (hanging wall and footwall) folds. A section of a hanging wall or foot wall where a thrust fault formed along a relatively weak bedding plane is known as a flat and a section where the thrust fault cut upward through

1176-433: The direction of extension or shortening changes during the deformation but the earlier formed faults remain active. The hade angle is defined as the complement of the dip angle; it is the angle between the fault plane and a vertical plane that strikes parallel to the fault. Ring faults , also known as caldera faults , are faults that occur within collapsed volcanic calderas and the sites of bolide strikes, such as

1225-431: The distinction, as the rock between the faults is converted to fault-bound lenses of rock and then progressively crushed. Due to friction and the rigidity of the constituent rocks, the two sides of a fault cannot always glide or flow past each other easily, and so occasionally all movement stops. The regions of higher friction along a fault plane, where it becomes locked, are called asperities . Stress builds up when

1274-506: The expansion of farming in the region, the population using water from the lake subsequently increased, and by 1958 the lake only held up to 22 square kilometres, with a water depth of about 0.8 metres. As of 2000, except for the southwest region, little lakewater remained, and the entire lake area has become a saltpan , with the centre of the lake holding silt swamps , and no longer holds any native birds. During times of intense sunshine, mirages can often be seen. Nowadays, Ayding Lake has

1323-409: The fault (called a piercing point ). In practice, it is usually only possible to find the slip direction of faults, and an approximation of the heave and throw vector. The two sides of a non-vertical fault are known as the hanging wall and footwall . The hanging wall occurs above the fault plane and the footwall occurs below it. This terminology comes from mining: when working a tabular ore body,

1372-532: The fault is the vertical component of the separation and the heave of the fault is the horizontal component, as in "Throw up and heave out". The vector of slip can be qualitatively assessed by studying any drag folding of strata, which may be visible on either side of the fault. Drag folding is a zone of folding close to a fault that likely arises from frictional resistance to movement on the fault. The direction and magnitude of heave and throw can be measured only by finding common intersection points on either side of

1421-413: The fault movement. Faults are mainly classified in terms of the angle that the fault plane makes with the Earth's surface, known as the dip , and the direction of slip along the fault plane. Based on the direction of slip, faults can be categorized as: In a strike-slip fault (also known as a wrench fault , tear fault or transcurrent fault ), the fault surface (plane) is usually near vertical, and

1470-406: The fault. A fault in ductile rocks can also release instantaneously when the strain rate is too great. Slip is defined as the relative movement of geological features present on either side of a fault plane. A fault's sense of slip is defined as the relative motion of the rock on each side of the fault concerning the other side. In measuring the horizontal or vertical separation, the throw of

1519-428: The footwall moves laterally either left or right with very little vertical motion. Strike-slip faults with left-lateral motion are also known as sinistral faults and those with right-lateral motion as dextral faults. Each is defined by the direction of movement of the ground as would be seen by an observer on the opposite side of the fault. A special class of strike-slip fault is the transform fault when it forms

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1568-531: The footwall. The dip of most normal faults is at least 60 degrees but some normal faults dip at less than 45 degrees. A downthrown block between two normal faults dipping towards each other is a graben . A block stranded between two grabens, and therefore two normal faults dipping away from each other, is a horst . A sequence of grabens and horsts on the surface of the Earth produces a characteristic basin and range topography . Normal faults can evolve into listric faults, with their plane dip being steeper near

1617-424: The fruit, the grapes stand out: more than 100 varieties of grape are cultivated in the area and it accounts for 90% of China's seedless grape crop. Other specialty agricultural products of the region are Donghu Hami melons and long-staple cotton . Fault (geology) In geology , a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as

1666-429: The geometric gap, and depending on its rheology , the hanging wall might fold and slide downwards into the gap and produce rollover folding , or break into further faults and blocks which fil in the gap. If faults form, imbrication fans or domino faulting may form. A reverse fault is the opposite of a normal fault—the hanging wall moves up relative to the footwall. Reverse faults indicate compressive shortening of

1715-491: The implied mechanism of deformation. A fault that passes through different levels of the lithosphere will have many different types of fault rock developed along its surface. Continued dip-slip displacement tends to juxtapose fault rocks characteristic of different crustal levels, with varying degrees of overprinting. This effect is particularly clear in the case of detachment faults and major thrust faults . The main types of fault rock include: In geotechnical engineering ,

1764-436: The lake basin was once filled with freshwater , which primarily originated from melted snow water from the mountains, as well as supplementary groundwater ; owing to the lesser use of water to irrigate cultivated land during the winter, the water level was higher. During the summertime, the water level declined as a result of increased use of irrigation water for farming , as well as significant natural evaporation . Due to

1813-464: The largest faults on Earth and give rise to the largest earthquakes. A fault which has a component of dip-slip and a component of strike-slip is termed an oblique-slip fault . Nearly all faults have some component of both dip-slip and strike-slip; hence, defining a fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional regimes, and others occur where

1862-408: The miner stood with the footwall under his feet and with the hanging wall above him. These terms are important for distinguishing different dip-slip fault types: reverse faults and normal faults. In a reverse fault, the hanging wall displaces upward, while in a normal fault the hanging wall displaces downward. Distinguishing between these two fault types is important for determining the stress regime of

1911-435: The most common. With the passage of time, a regional reversal between tensional and compressional stresses (or vice-versa) might occur, and faults may be reactivated with their relative block movement inverted in opposite directions to the original movement (fault inversion). In such a way, a normal fault may therefore become a reverse fault and vice versa. In a normal fault, the hanging wall moves downward, relative to

1960-494: The opposite direction. These faults may be accompanied by rollover anticlines (e.g. the Niger Delta Structural Style). All faults have a measurable thickness, made up of deformed rock characteristic of the level in the crust where the faulting happened, of the rock types affected by the fault and of the presence and nature of any mineralising fluids . Fault rocks are classified by their textures and

2009-412: The right time for—and type of— igneous differentiation . At a given time differentiated magmas would burst violently out of the fault-traps and head to shallower places in the crust where porphyry copper deposits would be formed. As faults are zones of weakness, they facilitate the interaction of water with the surrounding rock and enhance chemical weathering . The enhanced chemical weathering increases

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2058-510: The size of the weathered zone and hence creates more space for groundwater . Fault zones act as aquifers and also assist groundwater transport. Ayding Lake Aydingkol ( Uyghur : ئايدىڭكۆل , Айдиңкөл , Aydingköl ), Aydingkul (Mongol) or Ayding ( Chinese : 艾丁湖 ; pinyin : Àidīng Hú ) is a lake in the Turpan Depression , Xinjiang Uyghur Autonomous Region , PR China . At 154 m below sea level , it

2107-700: The south. Beyond the surrounding mountain ranges lie the Junggar Basin in the north and the Tarim Basin in the south. Some geographers also use the term Turpan-Hami Basin, which is understood as including the Turpan Depression along with the Hami Depression (located to the east of the Turpan Depression, and to the southwest of the city of Hami ) and the Liaodong Uplift separating the two depressions. A source using this terminology gave

2156-416: The stratigraphic sequence is known as a ramp . Typically, thrust faults move within formations by forming flats and climbing up sections with ramps. This results in the hanging wall flat (or a portion thereof) lying atop the foot wall ramp as shown in the fault-bend fold diagram. Thrust faults form nappes and klippen in the large thrust belts. Subduction zones are a special class of thrusts that form

2205-400: The surface, then shallower with increased depth, with the fault plane curving into the Earth. They can also form where the hanging wall is absent (such as on a cliff), where the footwall may slump in a manner that creates multiple listric faults. The fault panes of listric faults can further flatten and evolve into a horizontal or near-horizontal plane, where slip progresses horizontally along

2254-448: The terrain to sustain the water flow and guide the water right to the plants while minimizing evaporation all along the way. The historical record of the system extends back to the Han dynasty . The number of Karez systems in the area is slightly below one thousand and the total length of the canals is about 5,000 km (3,100 mi) in length. The Karez System is therefore considered one of

2303-759: The three great ancient projects in China along with the Great Wall and the Grand Canal . Recently, development of groundwater through tubewells has led to a general fall in water tables, and many karez systems have failed. Farming in the Turpan Basin is particularly famous for its fruit. Because of the dry and hot conditions, the fruits grown in the depression have very high concentrations of sugar. They are traditionally processed by drying in open drying barns. The cultivated fruit include: mulberry , peach , apricot , apple , pomegranate , pear , fig , walnut , as well as grapes , watermelons and true melons . Among

2352-582: The vicinity. In California, for example, new building construction has been prohibited directly on or near faults that have moved within the Holocene Epoch (the last 11,700 years) of the Earth's geological history. Also, faults that have shown movement during the Holocene plus Pleistocene Epochs (the last 2.6 million years) may receive consideration, especially for critical structures such as power plants, dams, hospitals, and schools. Geologists assess

2401-574: Was a key point on the ancient Silk Road and dates back to the 1st century BC. It was burnt down in wars in the 14th century. The Bezeklik Thousand Buddha Caves , which are located in the Flaming Mountains ' Mutou Valley , about 30 km (19 mi) east of the city of Turpan, have been hewn into the rock from the Tang dynasty –era up to the time of the Yuan dynasty (13th century). The caves are famous for their murals, which can still be found in about 40 of

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