Glacial Deposits Essay
The glacial deposits are features that results from glaciation’s process. In this paper, glacial deposits have been dealt in isolation of other glaciation processes. Some concepts in glaciation erosion such as plucking and abrasion have been discussed in depth to help understand the process in which some of these glacial deposits are formed. The two terms give a clear picture so as to understand the type and the nature of the glacial deposit features. Glacial deposits features such as drumlin, alluvial stratification, moraine, loess deposits and deposits in contact with ice among other have been explored in depth.
Within the paper also, various forms glacial depositions have dealt with. This gives a clear understanding of the processes of the formation of the glacial deposits features. These types of glacial depositions are: lodgement, ablation till, deformation flow and dumping Glacial Deposits By description, a glacial deposit is made up of varying sizes of boulders in matrix form dominated by clay, which are deposited underneath an ice sheet or a valley glacier. The sediments and the rocks found in the glacial deposits are added to the glacier by processes that are different.
The erosion by the glacier is principally by two methods, that is, plucking and the abrasion. In the process of the formation of glacial deposits, the glacier flows over the surfaces of the fractured bedrocks. These bedrocks are made soft by the glacier which are the lifted up and brought into the ice. This kind of erosion by the glacier is known as the plucking. It is produced when there is penetration of sub glacial water in fractures and separation of the ice and the rocks as a result of subsequent expansion and freezing of the ice.
The expansion of the ice in this case is acting as a lever that lifts the rocks up by loosening them. All the sediments in this way become the load of the glacier. The frozen rocks into the ice bottom in the process of erosion by the ice acts as grit. On the other hand, glacial deposits through the abrasion process occur when the fragment of the rock load and the ice moves over the bedrock (Bell, 1999, 34). This works as a sandpaper that polishes and smoothes the surface that is situated below. The rocks that are pulverized in this case are here referred to as rock flour.
The flour in this case is made by the grains of rocks of the sizes that range from 0. 002 to 0. 00625mm. In some cases, the produced amount of the rocks might be so high such that meltwater currents get a grayish color. These erosion processes leads to valley walls that are steeper and the slopes of the mountains assumes the settings of alpine. This can actually lead to rock slide and avalanching from which more materials can be added to the glacier land and deposited on another area or region. Glacial striations are good example of glacial abrasion.
These results when the ice that is at the bottom possesses in it chunks of rock that are large in size with bedrock mark scratches. The direction of the glacier can be determined by mapping the flutes direction. Chatter marks are observed to have the, shape of crescent rough lines depression in the underlying rock of the glacier that results from the abrasion process (Defant, 2005, 50). In this process, a boulder found in the ice develops which is then repetitively released as it is dragged by the glacier over the basal underlying rock.
A large surface part of the glacier is covered by the sediment and debris of the rock. This is prevalent especially near the glacier snout, where ice in this case through ablation has been lost and the sediment is deposited behind. The rate of the two types of the glacier erosions can either be affected similarly or differently by external factors. There are six significant factors that have been found to play an important role in determining the rate of the glacial erosion. This rate will further determine the nature and the type of the glacial deposit that will be formed as a result of the glacial erosion.
These factors include the following: the thickening of the ice, the glacial movement velocity, hardness, abundance and the shape of fragments of the rock that are found in the ice at the glacier bottom, relative erosion ease of the surface found under the glacier, thermal conditions at the base of the glacier, and the water pressure and the permeability at the base of the glacier (Allaby, 2000, 46). The incorporated materials in the glacier are then carried typically for a length of distance depending on the zone of ablation before the materials are deposited.
Glacial deposits are classified into distinct types, that is, the glacial till, the outwash and fluvial. The fluvial and outwash is the type of glacial deposits where we have deposition of the sediments by the water. Through various processes, such sediment deposits are stratified. In the stratification process, the boulders and the fine particles are separated. In the case of glacial till, we have direct deposition of materials from the glacier. A till is composed of undifferentiated mixture of materials ranging from boulders to clay size and the moraine composition.
The rocks that are of larger pieces deposited on the surface or encrusted in till are referred to as glacial erratics. They may vary in their sizes from boulders to till. However, the rocks may be transported for a distance that is greater. These rocks can be of different types depending on the nature or the type of bedrock they were encrusted. The glacial erratics patterns may offer a clue of the past motions of the glacier (Orme, 2000, 18). On the other hand, material deposition from glacier and the exposition of the retreated glacier leads to the formation of the glacial moraines.
The resulting features in this case appears in till mounds that are linear, a non-sorted rock mixtures, boulders and gravel found in the matrix of material like fine powdery. The end or the terminal moraines are formed at the terminal end or foot of a glacier. The formation of the lateral moraines is on the glacier sides. The formation of medial moraines takes place when two glaciers which are moving differently in the direction that is similar. They include the lateral moraine and coalesce where they both combine intensively with the formation of a moraine between them from the glacier that is merged (Anderson, 2005, 67).
The ground moraine is less apparent and is referred to as the glacial drift, which usually covers the underneath surface, much of which is the down-slope of the glacier from the line of equilibrium. The rock flour is contained by the meltwater, whereby the rock flour is an extremely fine ground powder from the rock that is underlying by the movement of the glacier. The term moraine has its origin from France which when adequately coined gives the description of alluvial rims and embankments which are located at the glacier margins in the French Alps.
In the modern geology, this term has many uses and in a series of formations, it is applied on various dimensions from the nature of its constituent till. Some examples of glacial deposits include the following. Firstly, is the drumlin. They are formed when there is modification of the landscape by the glacier. Drumlins are streamlined distinctive hills. They are canoe shaped, asymmetrical hill with profiles of aerodynamic which are mainly made of till. Their height ranges from 15 to 50 meters and they can even stretch further to a kilometer.
The side of the hill that is tilted faces the direction of the ice advancement, while the slope that is longer follows the direction of the ice movement. Drumlin camps or drumlin fields are the major groups of such drumlins. A good example of such drumlin field is found in Rochester, which is estimated to contain about 10,000 of such drumlins in it. Despite the fact that the process of drumlin formation is not clearly understood, its formation can be related to their shape where they may have plastic products zone deformation of the ancient glacier.
Many of the drumlins are believed to have been formed during the alteration of the earlier glacier deposits and the over advancement of glacier (Mannion, 1999, 21). Either, glaciers may be described in terms of alluvial stratification. This is another glacial deposit feature whose formation occurs when there is rising of the water from the zone of ablation, flowing away from the glacier which then it carries eroded fine sediment. Its capacity to transport suspensions of objects in it depends with the speed of the water.
This means that when the speed of water goes down, then the capacity to carry the suspensions of material in it also goes down. The water carrying these materials deposits them as it runs forming an alluvial plain. This will be referred to as a valley train if the phenomenon takes place in a valley. The sediment will be referred to as bay mud if the deposition has occurred in an estuary. Valley trains and outwash plains are normally accompanied by kettles basins. In the till deposits, there will also be the production of glacial depressions.
The formation of these depressions takes place when large blocks of ice get stuck in the holes of the alluvium within the glacial sediments (Goudie, 1992, 35). Thirdly, are the deposits in contact with an ice. These are glacial deposits that are formed in the process where there is a reduction in the size of the glacier to a point that is critical, leading to a stagnation of the glacier flow as well as the ice becoming stationary. Meanwhile, the melt water moves within, over and beneath the ice leaving the deposits of the alluvial stratified.
For this reason, the ice leaves deposits that are stratified in the form of terraces, clusters and columns as it melts down. When these deposit in glacial deposit, they are known as deposits in contact with ice. If such deposits happen to take the form of mounds or tipped sides columns, they are referred to as kames. The formation of certain kames takes place when there is deposition of sediments by meltwater through the openings in the interior of the ice. In other cases, their formation is only as a result of deltas or fans towards the exterior of the ice which is produced by the meltwater.
If a valley is occupied by glacial ice, this can result into the formation of kame or terraces along the valley sides (Shroder, 1993, 42). The other kind of deposit which can be formed in contact with ice has got the characteristics such as narrow and long crests sinuous which are fundamentally made up of gravel and sand deposited by meltwater streams flowing beneath or within the glacier. After the melting of the ice, the linear eskers or ridges remain as the features of the landscape. The height of some of these crests exceeds 100 meters and their length goes beyond 100 kilometers.
Fourthly, are the Loess deposits. Very fine rock flour or glacial sediments is picked up by blowing wind over the surface that is bare and may be carried and deposited at a distant that is greater from the deposition site of the original fluvial. These deposits of eolian loess deposits can be very deep up to or more than 100 meters. This has been witnessed in countries such as the Midwestern United States and China (Grove, 1990, 56). In the process of the formation of this kind of glacial deposits, katabatic wind plays a significant role.
Other glacial deposits features that can be formed include the dropstones. They are boulders which are curious looking and are found in sedimentary deposits. They are believed to have been transported by the ice drift in which they were deposited as the ice melted. Secondly, we have the frost polygons. They are viewed as the snow retreats in alpine and arctic areas where the soil experiences seasonal thawing and freezing cycles. They form a kind of honeycomb network. In relation to their composition, the shape of frost polygons is of various sizes. Elsewhere, we have the glacial varves.
They are deposits that are regularly banded. They are formed by cyclical sedimentation, with dark laminae, fine gains which alternate with lighter layers of coarse grains. They are formed at the cold floors of freshwater lakes fed by meltwater glacial streams. Lastly, are the tillites. These imply the kind of deposits that have got materials which are non-stratified. The materials are deposited by the glacial ice direct. Tillites are composed of medium boulders and clay. They are developed from cementing and compacting of glacial tills (Beckinsale, 1991, 27).
In glacial deposits, the features that results are from different forms of deposition. These depositions are classified as follows: firstly, is the lodgment till. This kind of deposition is similar to the ground moraine. Here, materials are smeared on the floor of the valley when the weight of the materials becomes too great and heavy to be transported by the glacier. Secondly, is the ablation till. This one is just a combination of supraglacial and englacial moraine. They are deposited when the glacier that is stationary starts to melt and then the materials that were in situ gets dropped. Thirdly, is the dumping.
This is deposition where materials are moved by the glacier to their lowermost or outermost ends which are then dumped. Lastly, is the deformation flow. This is usually the change of the rock shape and land because of the glacier formation process. Work Cited Allaby Michael, Basics of Environmental Science. London, Routledge, 2000, pp. 46 Anderson Douglas, The Use of Caves in Peninsular Thailand in the Late Pleistocene and Early Middle Holocene. Asian Perspectives: the Journal of Archeology for Asia and the Pacific, Vol. 44, 2005, pp. 67 Beckinsale Robert, The History of the Study of Landforms or the Development of Geomorphology 1890-1950.
London, Routledge, 1991, pp. 27 Bell Simon, Landscape: Pattern, Perception, and Process. New York, Spon Press, 1999, pp. 34 Defant Marc, Ice Over Earth. World and I, Vol. 16, 2005, pp. 50 Goudie Andrew. Environment Change. London, Clarendon Press, 1992, pp. 35 Grove Jean, The Little Ice Age. London, Routledge, 1990, pp. 56 Mannion, A. , Natural Environmental Change: The Last 3 Million Years. London, Routldge, 1999, pp. 21 Orme Antony, The Physical Geography of North America. Oxford, Oxford University Press, 2000, pp. 18 Shroder John, Himalaya to the Sea: Geology, Geomorphology, and the Quaternary. London, Routledge, 1993, pp. 42
Subject: Glacial Deposits,
University/College: University of Chicago
Type of paper: Thesis/Dissertation Chapter
Date: 28 September 2016
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