Misplaced Pages

#957042

35-562: The Diamante is fed by ice-thaw-fed streams that flow into its source, the Diamante Lake. It has an average flow of 33 cubic metres per second (1,200 cu ft/s), with its maximum during the spring and summer; the October–March period accounts for 70 percent of the annual water volume. The upper course of the river turns south and then back north, and becomes entrenched within the deep, narrow Agua del Toro Canyon, where it

70-409: A glacier or ice sheet. It may consist of partly rounded particles ranging in size from boulders (in which case it is often referred to as boulder clay) down to gravel and sand, in a groundmass of finely-divided clayey material sometimes called glacial flour . Lateral moraines are those formed at the side of the ice flow, and terminal moraines are those formed at the foot, marking the maximum advance of

105-417: A long moraine bank marking the ice margin. Several processes may combine to form and rework a single moraine, and most moraines record a continuum of processes. Reworking of moraines may lead to the formation of placer deposits of gold as is the case of southernmost Chile . Moraines can be classified either by origin, location with respect to a glacier or former glacier, or by shape. The first approach

140-604: A major feature of river entrenchment, as an impact of river rejuvenation. On the other hand, scholars argue that incised meanders and entrenched meanders are features formed before river rejuvenation. Incised meanders occur at the base of the river and they occur when the river base level has reduced, thus giving the river enough power for vertical erosion to take place. Some studies also indicate that anthropogenic factors such as clearing of vegetation , development of dams , and reservoir and urbanization are also causes of river entrenchment. For example, gravel mining along

175-499: A narrow trench or valley cut into a plain or relatively level upland. Because of lateral erosion streams flowing over gentle slopes over a time develops meandering (snake like pattern) course. Meanders form where gradient is very gentle, for example in floodplain and delta. Meandering is the feature of the middle and final course of the river. But very deep and wide meanders can also be found cutting hard rocks. Such meanders are called incised or entrenched meanders. The exception

210-428: A terminal moraine. They form perpendicular to the lateral moraines that they reside between and are composed of unconsolidated debris deposited by the glacier. They are created during temporary halts in a glacier's retreat. In permafrost areas an advancing glacier may push up thick layers of frozen sediments at its front. An arctic push moraine will then be formed. A medial moraine is a ridge of moraine that runs down

245-583: Is dammed to produce hydroelectricity by the Agua del Toro Dam , at about 69° W, and a few kilometres later by the Los Reyunos Dam . Together these two power stations generate 500 MW . Upon reaching the plain, the Diamante loses part of its volume through infiltration and evaporation. It turns in a gentle arc, passing south of the city of San Rafael , in the geographical center of Mendoza, where it

280-469: Is also very costly when restoration is to be initiated. river entrenchment happens because of the water having the power to cause erosion on the river bed. This increased velocity has shown a negative effect on the riparian habitat , because of increased erosion of the area. For example, a study by Simon revealed that channel incision is a major characteristic of entrenched rivers , and it affects variables in riparian vegetation and growth of fish in

315-409: Is either valley meander or meander valley with the latter term being preferred in literature. The meanders that form part of either an entrenched river or meander valley are most commonly known as incised meanders . They are commonly classified as either an ingrown meander or an entrenched meander . For a long time, it was argued that ingrown meander occurs when downcutting process

350-403: Is slow and the river can cause lateral erosion , leading to an asymmetric valley . In addition, it was also argued for a long time that an entrenched meander forms when there is a rapid incision of the river bed such that the river does not have the opportunity to erode the lateral side. This leads to symmetrical valleys with a gorge -like appearance. However, more detailed studies have shown

385-450: Is suitable for moraines associated with contemporary glaciers—but more difficult to apply to old moraines , which are defined by their particular morphology, since their origin is debated. Some moraine types are known only from ancient glaciers, while medial moraines of valley glaciers are poorly preserved and difficult to distinguish after the retreat or melting of the glacier. Lateral moraines are parallel ridges of debris deposited along

SECTION 10

#1732772219958

420-422: Is that entrenched meanders are formed during the upliftment of land where river is young. They widen and deepen over time and can be found as deep gorges or canyons in hard rock. In the case of an entrenched stream or river, it is often presumed that the watercourse has inherited its course by cutting down into bedrock from a pre-existing plain with little modification of the original course. The down-cutting of

455-540: Is used for irrigation (together with the Atuel River ). The river splits in multiple branches shortly before reaching the Desaguadero (here called Salado), on the border with the province of San Luis . 34°28′S 64°45′W  /  34.467°S 64.750°W  / -34.467; -64.750 Entrenched river An entrenched river , or entrenched stream is a river or stream that flows in

490-458: Is very difficult to offer detailed information of past tectonic activity, the basic temporal and spatial scale can show evidence of how this movement leads to the formation of an entrenched river. Various authors have used an entrenched river as evidence of tectonic movement in the past, and in this way they have proven the significant role of tectonic uplifts in the formation of an entrenched river. Several studies have cited incised meander

525-636: The Russian River developed the Middle Reach pit, which in turn led to the creation of the entrenched river. According to Posamentier, in the 1950s and 1980s, the Russian River had gravel pits and dry creek . However, over time the river has become entrenched due to mining (p. 1777). Urbanization and clearing of vegetation increase runoff water, which in turn increases water volume , especially during rainy seasons. Therefore,

560-718: The areas (p. 528). Lowering of the channels means that the ground water level has also reduced. Specifically, the development of the entrenched river reduces the amount of ground water due to water loss through infiltration . The movement of the base level changes tributaries and the entrenchment of a tributary channel. Studies of various rivers have revealed that the process of river entrenchment has been associated with adjustment of river positions through bank erosion , as well as widening. River entrenchment causes negative impacts, such as accelerated stream bank erosion , land loss, loss of aquatic habitat , loss of land productivity, lowering of water table and sedimentation of

595-603: The center of a valley floor. It forms when two glaciers meet and the debris on the edges of the adjacent valley sides join and are carried on top of the enlarged glacier. As the glacier melts or retreats, the debris is deposited and a ridge down the middle of the valley floor is created. The Kaskawulsh Glacier in the Kluane National Park , Yukon , has a ridge of medial moraine 1 km wide. Supraglacial moraines are created by debris accumulated on top of glacial ice. This debris can accumulate due to ice flow toward

630-409: The consequences of incised meander are associated with accelerated stream bank erosion , land loss , aquatic habitat loss, as well as lowering the water table. Additionally, the study also found that incised meanders also cause loss of land productivity and downstream sedimentation (p. 2). The factors are likely to affect not only the economic development on the land where it passes but it

665-431: The development of ingrown meanders versus entrenched meanders depends on a complex mixture of factors such as bedrock lithology, tectonic activity, and climate. As observed above, an entrenched river can be caused by either tectonic uplift in the area or when the lowering of the sea level occurs. It can also be caused by increased level of downcutting or a collapse of moraine -dammed lake downstream, or capture of

700-511: The glacier has melted. Moraines may form through a number of processes, depending on the characteristics of sediment, the dynamics on the ice, and the location on the glacier in which the moraine is formed. Moraine forming processes may be loosely divided into passive and active . Passive processes involve the placing of chaotic supraglacial sediments onto the landscape with limited reworking, typically forming hummocky moraines. These moraines are composed of supraglacial sediments from

735-428: The glacier margin (up to 80 degrees) than further away (where slopes are typically 29 to 36 degrees. Ground moraines are till-covered areas with irregular topography and no ridges, often forming gently rolling hills or plains, with relief of less than 10 meters (33 ft). Ground moraine is accumulated at the base of the ice as lodgment till with a thin and discontinuous upper layer of supraglacial till deposited as

SECTION 20

#1732772219958

770-544: The glacier retreats. It typically is found in the areas between end moraines. Rogen moraines or ribbed moraines are a type of basal moraines that form a series of ribs perpendicular to the ice flow in an ice sheet . The depressions between the ribs are sometimes filled with water, making the Rogen moraines look like tigerstripes on aerial photographs . Rogen moraines are named after Lake Rogen in Härjedalen , Sweden ,

805-578: The glacier. Other types of moraine include ground moraines ( till -covered areas forming sheets on flat or irregular topography ) and medial moraines (moraines formed where two glaciers meet). The word moraine is borrowed from French moraine [mɔ.ʁɛn] , which in turn is derived from the Savoyard Italian morena ('mound of earth'). Morena in this case was derived from Provençal morre ('snout'), itself from Vulgar Latin * murrum ('rounded object'). The term

840-715: The globe involving river restoration have been conducted, and a good example of such projects is Maggie Creek, Nevada . The project was completed in 1990 on upper Maggie Creek in Nevada . It was a partnership between the government and a private ranch, and the project entailed straightening of many miles of unstable gravel bed regarded as the C4/D4 type. Moraine A moraine is any accumulation of unconsolidated debris ( regolith and rock ), sometimes referred to as glacial till , that occurs in both currently and formerly glaciated regions, and that has been previously carried along by

875-415: The ice surface. Active processes form or rework moraine sediment directly by the movement of ice, known as glaciotectonism. These form push moraines and thrust-block moraines, which are often composed of till and reworked proglacial sediment. Moraine may also form by the accumulation of sand and gravel deposits from glacial streams emanating from the ice margin. These fan deposits may coalesce to form

910-463: The increased level of vertical erosion of the river increases the power of the water, leading to erosion of the river. A study of San Pedro River and another river in the southwest have indicated that floods were the main cause of river entrenchment in the 18th century. The study shows that increased population and human activities in these places increased floods and, consequently, the volume of runoff water (Hereford 43). Rosgen indicates that

945-503: The landform's type locality. Closely related to Rogen moraines, de Geer moraines are till ridges up to 5m high and 10–50m wide running perpendicular to the ice flow. They occur in large groups in low-lying areas. Named for Gerard De Geer , who first described them in 1889, these moraines may have developed from crevasses underneath the ice sheet. The Kvarken has a very high density of de Geer moraines. End moraines, or terminal moraines , are ridges of unconsolidated debris deposited at

980-411: The moraine. There are two types of end moraines: terminal and recessional. Terminal moraines mark the maximum advance of the glacier. Recessional moraines are small ridges left as a glacier pauses during its retreat. After a glacier retreats, the end moraine may be destroyed by postglacial erosion. Recessional moraines are often observed as a series of transverse ridges running across a valley behind

1015-468: The river by another river. Moreover, the process of river rejuvenation can also be the cause of river entrenchment , especially when the process has occurred due to tectonic uplift . River rejuvenation increases the power of the flowing water and, therefore, the process of erosion is accelerated. Studies show that tectonic movement , particularly movement associated with uplift , can influence spatial patterns of erosion and sedimentation . Although it

1050-474: The river downstream. However, in order to offset these problems, channel restoration measures focusing on restoration of the river in its original or to its previous characteristics are available. Though to achieve good results, a good understanding of the river patterns and profile of stable channels is a critical requirement. The process also needs an elaborate procedure to be followed to ensure all important factors and actions are followed. Numerous projects across

1085-442: The river system could be the result not only of tectonic uplift but also of other factors such as river piracy, decrease of load, increase of runoff, extension of the drainage basin, or change in base level such as a fall in sea level. General, nongeneric terminology for either a river or stream that flows in a narrow trench or valley, for which evidence of a preexisting plain or relatively level upland can be either absent or present

Diamante River - Misplaced Pages Continue

1120-454: The sides of a glacier. The unconsolidated debris can be deposited on top of the glacier by frost shattering of the valley walls or from tributary streams flowing into the valley, or may be subglacial debris carried to the surface of the glacier, melted out, and transported to the glacier margin. Lateral moraines can rise up to 140 meters (460 ft) over the valley floor, can be up to 3 kilometers (1.9 mi) long, and are steeper close to

1155-427: The snout or end of the glacier. They usually reflect the shape of the glacier's terminus . Glaciers act much like a conveyor belt, carrying debris from the top of the glacier to the bottom where it deposits it in end moraines. End moraine size and shape are determined by whether the glacier is advancing, receding or at equilibrium. The longer the terminus of the glacier stays in one place, the more debris accumulate in

1190-419: The surface in the ablation zone , melting of surface ice or from debris that falls onto the glacier from valley sidewalls. Washboard moraines , also known as minor or corrugated moraines , are low-amplitude geomorphic features caused by glaciers. They consist of low-relief ridges, 1 to 2 meters (3 ft 3 in to 6 ft 7 in) in height and around 100 meters (330 ft) apart, accumulated at

1225-467: Was introduced into geology by Horace Bénédict de Saussure in 1779. Moraines are landforms composed of glacial till deposited primarily by glacial ice. Glacial till, in turn, is unstratified and unsorted debris ranging in size from silt -sized glacial flour to large boulders. The individual rock fragments are typically sub-angular to rounded in shape. Moraines may be found on the glacier's surface or deposited as piles or sheets of debris where

#957042