Geography
Glacial Depositional Landforms
Glacial depositional landforms are features created by the deposition of material by glaciers. These landforms include moraines, drumlins, eskers, and outwash plains. Moraines are ridges of glacial till, while drumlins are elongated hills formed by glacial action. Eskers are long, winding ridges of sand and gravel, and outwash plains are flat areas of sediment deposited by meltwater from glaciers.
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11 Key excerpts on "Glacial Depositional Landforms"
eBook - PDF- Alan F. Arbogast(Author)
- 2017(Publication Date)
- Wiley(Publisher)
Geo Media Depositional Glacial Landforms Like many other Earth processes, the formation of glacial land- forms can be better understood when visualized in animated form. To do so, go to the Geo Media Library and select Depositional Glacial Landforms. This animation illustrates the way moving and melting ice shapes the landscape. It also contains a nice video of glaciers in Peru. After you complete the interactivity, be sure to answer the questions at the end to test your understanding. Key Concepts to Remember About Glacial Deposition and Resulting Landforms 1. Two primary kinds of glacial deposits occur: till and outwash. Glacial till is deposited in direct contact with the ice, whereas glacial outwash accumulates through meltwater streams flowing in front of the ice. 2. Glacial till is relatively unsorted and accumulates either as basal (lodgement) till smeared under the bottom of the glacier or as ablation till laid down as the ice melts. 3. A distinctive depositional landform created by glaciers is a moraine (end, lateral, or medial), which is a ridge of till that forms when the ice front or margin is in one place for a relatively long period of time. Drumlins are streamlined till landforms created by the weight and pressure of the overlying flowing ice. 4. Glacial outwash is relatively well sorted because it is deposited by flowing meltwater in front of the ice. The associated streams are typically braided and create a broad, flat surface known as an outwash plain. Sometimes glacial outwash buries a block of ice that broke off the front of a receding glacier. When this ice block subsequently melts, it forms a water-filled depression called a kettle lake. 5. Kames and eskers are distinctive meltwater landforms. A kame is an irregularly shaped hill that essentially consists of an alluvial fan or a deltaic deposit that forms in contact with the ice.
eBook - PDF- Alan H. Strahler(Author)
- 2013(Publication Date)
- Wiley(Publisher)
T o the south, at the bottom of the image C , the terrain becomes more dissected, with more pronounced valleys and ridges, as it slopes upward to the higher elevations of the plateau. Courtesy NASA A C B Moraines are piles of debris and sediment that accumulate at the front or sides of a glacier. Eskers, drumlins, kettles, and kames are land- forms of till and outwash plains left by ice sheets. Glacial Landforms 575 17.16 Landforms produced by ice sheets In glacial landscapes, a variety of features mark both the expansion and retreat of ice sheets. Ice Delta Iceberg Outwash plain Ice blocks Braided streams Esker Kame Kettles Outwash plain Terminal moraine Till plain Drumlins Eskers Recessional moraine Tunnels Ice DURING GLACIATION At its maximum extent, the front edge of the glacier melts and evaporates at a rate matching that of its forward motion, so the position of the front edge of the glacier is stationary. AFTER MELTING When the glacier retreats, it leaves behind deposits in the form of moraines, eskers, drumlins, and kames. 576 Chapter 17 Glacial and Periglacial Landforms 17.17 Formation of a moraine A moraine forms at the end of an advancing glacier, which carries debris forward, like a conveyor belt, toward the glacial front. As the ice moves forward, melting and evaporation reduce the glacier’ s bulk and leave behind a deposit of glacial debris on the ice surface. Surface and internal debris then accumulate at the glacial front, along with some water-laid sediment, forming the moraine. 1 At the maximum extent of the glacier, debris accumulates at the ice front. Sediment under the glacier is sheared, compressed, and compacted by the weight and motion of the ice, forming lodgment till. Meltwater sorts and carries sediment beyond the moraine, forming the outwash plain. 2 When the glacier retreats, the terminal moraine is left as a series of irregular piles of debris, often mixed with jumbled water-laid sediments.
eBook - PDFPhysical Geography
Great Systems and Global Environments
- William M. Marsh, Martin M. Kaufman(Authors)
- 2012(Publication Date)
- Cambridge University Press(Publisher)
599 Glacial Deposition and Depositional Landforms for the occurrence of large stones on the ocean floor far from shore. But most glaciers do not end up in the sea, and instead deposit their loads of debris on land. Since ablation is concentrated in the lower part of the glacier, most depo- sition takes place near the snout. This holds for both alpine and continental glaciers. As the glacier moves ahead and melts, its load is deposited as though it was falling off the end of a conveyor belt. There are two chief modes of glacial deposition. One is deposition directly from the ice as it melts, and the other is deposition by meltwater flowing from the glacier. Let us begin this section with the terms used to describe the materials and the deposits they form. The material deposited from the ice is called till and the landforms produced by such deposits are called moraines. All moraines are made up of till. Sediments laid down by meltwater are called glaciofluvial deposits and the same term is used for both the material and deposits. All material deposited by glaciers, both on land and at sea, is collectively known as glacial drift. As the photographs in Figure 23.25 plainly show, till and gla- ciofluvial deposits are markedly different. Till is a heteroge- neous mixture of unstratified materials ranging in size from massive boulders to clay-sized particles. Its composition, the manner of its deposition, and the resultant landforms vary widely, from hills and mounds arranged more or less in ridges to rolling plains. Glaciofluvial deposits, by contrast, are strati- fied and composed chiefly of sand and gravel. They vary in form from mounds to fan-like aprons and winding ridges. Glaciofluvial deposits are usually found in close proximity to moraines. Till Deposits and Landforms: Moraines are named for the loca- tion where they form in and around the glacier, as illustrated in Figure 23.26.
eBook - PDF- James Petersen, Dorothy Sack, Robert Gabler, , James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2014(Publication Date)
- Cengage Learning EMEA(Publisher)
Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. C H A P T E R 1 6 • G L A C I A L S Y S T E M S A N D L A N D F O R M S 432 Depositional Landforms of Alpine Glaciation Glacial deposits consist of clastic sediments of a wide range of sizes, often mixed with layers of plant matter and soil. In addi-tion to the poorly sorted till deposited directly by glacial ice ( ■ Fig. 16.20), glacial terrain includes the better sorted and stratified sediment deposited by meltwater streams, lakes, and winds that occur in association with glaciers. Glaciofluvial is the term used to specify the fluvial deposits related to glacial meltwater. All deposits of glacial ice, its meltwater, associated lakes, and related wind, and therefore including till and glacio-fluvial deposits, are included within the general term drift . Active alpine glaciers deposit load primarily along the sides and toe of the ice mass. Landforms constructed from gla-cial deposits, typically ridges of till along these margins of gla-ciers, are moraines . Till deposited as ridges paralleling the side margins of a glacier are lateral moraines ( ■ Fig. 16.21a). Where two tributary valley glaciers join together, their lateral moraines merge downflow, creating a medial moraine in the center of the trunk glacier. Medial moraines cause the charac-teristic dark stripes seen on the surface of many alpine glaciers (Fig. 16.21b). At the toe of a glacier, sediment carried forward by the “conveyor belt” of ice, or pushed ahead of the glacier, is deposited in a jumbled heap of material of all grain sizes, forming a curved depositional ridge called an end moraine they occupy.
eBook - PDF- Vijay K. Sharma(Author)
- 2010(Publication Date)
- CRC Press(Publisher)
An excessively moist fine-textured lodge-ment till collapses into the cavities of sliding ice, and the supraglacial till of coarser fragmentary debris of low moisture content slumps into local depressions on the surface of alpine glaciers. S TRATIFIED D RIFT Sediments of glacial origin are reworked, and deposited, by the meltwater activity. The sediments laid down in contact with the ice, called ice-contact deposits , are only a small part of the glaciogenic load of glaciers. The remaining large proportion of the meltwater load is carried beyond the glacier margins as proglacial drift . It is gla-ciofluvial when laid down on land adjacent to the glacier ice, glaciolacustrine when deposited in freshwater lakes, and glaciomarine when laid down in the seawater. LANDFORMS OF DRIFT DEPOSITION Landforms of glaciogenic sediments evolve in response to the activity of glacier ice that releases and deforms its entrained load in many different ways, and the manner of sedimentation from the glacier melt at and within the ice. Hence, the environment of drift deposition offers a suitable framework for genetic classification of the depo-sitional landforms of drift composition (Table 7.3). The glacier ice is active when advancing or retreating over its bed and stagnant when a thin retreating ice breaks away from the main ice lobe and disintegrates in situ . The active and stagnant ice evolves a variety of depositional landforms. The melting of glacier ice and attendant supraglacial, englacial, and subglacial meltwater flow in contact with the ice evolves ice-contact landforms of stratified drift composition. The meltwater flow directed 190 Introduction to Process Geomorphology away from the glacier margins is called proglacial. The proglacial environment of deposition evolves glaciofluvial landforms on land, glaciolacustrine landforms in freshwater glacial lakes, and glaciomarine landforms in the seawater.
eBook - ePubGlacial Geology
Ice Sheets and Landforms
- Matthew M. Bennett, Neil F. Glasser(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
48, figure 12, p. 948]9.2 SUBGLACIAL LANDFORMS FORMED BY ICE OR SEDIMENT FLOWThis category of landforms is divided into those which have been ice-moulded and those that have not. Ice-moulded landforms are significant because they provide information about the direction and velocity of glacier flow.9.2.1 Ice-Moulded Subglacial LandformsThree broad families of ice-moulded subglacial landforms (bedforms) have been identified on the basis of size (Figure 9.15 ). Although each may be genetically distinct, these are as follows.Figure 9.15 Schematic representation of principal spatial frequencies and lengths of streamlined subglacial landforms. The data suggest that there are three populations of subglacial bedform: (i) flutes; (ii) drumlins and megaflutes; and (iii) megascale glacial lineations. [Reproduced with permission of John Wiley & Sons Ltd from: Clark (1993) Earth Surface Processes and Landforms, 18, figure 6, p. 9]1. Flutes. Typically these are low (< 3 m), narrow (< 3 m), regularly spaced ridges which are usually less than 100m long and are aligned parallel to the direction of ice flow (Figure 7.8B). They have a uniform cross-section and usually start from either: (i) a large boulder; (ii) a collection of boulders; or (iii) a bedrock obstacle. They are typically composed of lodgement till, although they may also contain fluvial sands and gravels. Clusters of boulders may occur within the body of the flute. They are a common landform in front of many glaciers today.2. Drumlins, megaflutes and rogen (ribbed) moraines. Drumlins are typically smooth, oval-shaped or elliptical hills composed of glacial sediment (Figures 9.16 and 9.17
eBook - PDF- James Petersen, Dorothy Sack, Robert Gabler, , James Petersen, James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 560 C H A P T E R 1 9 • G L A C I A L S Y S T E M S A N D L A N D F O R M S ● FIGURE 19.33 Hilly topography of an end moraine deposited by a continental ice sheet, eastern Washington. What makes the terrain at the left of the photo appear bumpier compared to the smoother surface of the plain at the right? ● FIGURE 19.34 Glacial deposits are widespread in the Great Lakes region. Why do the many end moraines have such a curved pattern? Lake Superior Lake Michigan Lake Huron Lake Erie Till plains End moraines Outwash plains and valley trains Glacial lake deposits Undifferentiated drift of earlier glaciations Driftless regions Principal glacial deposits in the Great Lakes region Drift deposited during middle and late Wisconsinan glaciation thick deposits of till make broad, rolling plains of low relief. Small hills and slight depressions, some filled with water, characterize most till plains, reflecting the uneven glacial deposition. The gen- tly rolling till plains of Illinois and Iowa are an excellent example of this glacial landform. Beyond the belts of hills that represent termi- nal and recessional moraines lie outwash plains composed of meltwater deposits. These extensive areas of relatively low relief consist of glaciofluvial deposits that are sorted as they are transported by meltwater from the ice sheets. Outwash plains, which may cover hundreds of square kilometers, are analogous to the valley trains of alpine glaciers. Small depressions or pits, called kettles, mark some outwash plains, till plains, and moraines.
eBook - PDF- Timothy Foresman, Alan H. Strahler(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
• Through erosion, glaciers shape stream valleys into glacial troughs, which can become fiords if later submerged by ris- ing sea level. • Moraines of rubble and debris mark the sides (lateral mo- raines) and ends (terminal moraines) of glaciers, as shown in the diagram. When two tributary glaciers come together, they form a medial moraine down the middle of the trunk glacier. Formation of a moraine • Figure 14.10 • Moving ice sheets leave behind till plains and outwash plains. Till plains are often marked with eskers and drum- lins. Outwash plains contain kettles and kames. • Plains shaped by glacial action can be fertile and productive. Glacial sand and gravel are important resources. 3 4 Terminal moraine Till plain Melt-out till Outwash plain Lodgement till 120°E 80°E 20°E 20°W 40°N 30°N 60°W 140°E 180° 100°W 30°N 30°N 30°N 40°N 40°N 30°N 140°W Permafrost Zone of subsea permafrost Zone of continuous permafrost Zone of discontinuous permafrost Zone of alpine permafrost Changes in Earth–Sun geometry • Figure 14.19 Global Climate and Glaciation 445 • An ice age includes alternating periods of glaciation, deglacia- tion, and interglaciation. During the past 2.5 million years or so, the Earth has been experiencing the Late-Cenozoic Ice Age. • The most recent glaciation, the Wisconsin Glaciation, changed the course of North American rivers. Huge ice- dammed lakes filled and then drained abruptly. Sea level dropped to about 125 m (410 ft) below present. • The Ice Age was most likely brought on by the motions of the continents, which changed patterns of oceanic and atmospheric circulation to produce ice covers at the poles. • Individual periods of glaciation and interglaciation are most likely related to cyclic changes in Earth–Sun distance and the Earth’s axial tilt, as shown in the diagram.
No longer available |Learn more- James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
What characteristics of the bedrock caused ice to form these narrow lake basins? NASA ● FIGURE 19.36 Drumlins, such as this one in Montana, are streamlined hills elongated in the direction of ice flow. Jim Petersen ● FIGURE 19.37 An esker near Albert Lea, Minnesota. What economic importance do eskers have? Henry Kyllingstad/Science Source Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. G L A C I A L L A K E S 561 where the land sloped toward, instead of away from, the ice front (see Fig. 19.32a). In both situations, ice-marginal lakes filled with meltwater. They drained and ceased to exist when the retreat of the ice front uncovered an outlet route for the water body. During their existence, fine-grained sediment accumulated on the floors of these ice-marginal lakes, filling in topographic irregu- larities. As a result of this sedimentation, extremely flat surfaces characterize glacial plains where they consist of glaciolacustrine deposits. An outstanding example of such a plain is the valley of the Red River in North Dakota, Minnesota, and Manitoba. This plain, one of the flattest landscapes in the world, is of great agri- cultural significance. The plain was created by deposition in a vast Pleistocene lake held between the front of the receding continental ice sheet on the north and moraine dams and higher topography to the south. This ancient body of water is named Lake Agassiz for the Swiss scientist who early on championed the theory of an ice age.
eBook - PDFGeomorphology: The Research Frontier and Beyond
Proceedings of the 24th Binghamton Symposium in Geomorphology, August 25, 1993
- J.D. Vitek, J.R. Giardino(Authors)
- 2013(Publication Date)
- Elsevier Science(Publisher)
Geomorphology, 7(1993)129-140 129 Elsevier Science Publishers B.V., Amsterdam Glacial geomorphology: modeling processes and landforms Jonathan M. Harbor Department of Geology, Kent State University, Kent, OH 44242, USA (Received March 11, 1993; accepted April 23, 1993) ABSTRACT The primary goal of glacial geomorphology is to provide physically-based explanations of the past, present and future impacts of glaciers and ice sheets on landform and landscape development. To achieve this requires the integration of studies of landform with studies of the processes responsible for form development (over a wide range of spatial and temporal scales). During the twentieth century significant improvements in approaches to recognizing and describing glacial landforms have been matched by impressive advances in understanding and modeling ice flow and glacial erosion and deposition processes. At present process models are being tested explicitly in terms of predicting the development of known forms (which also provides new insight into the controls on form development). Evaluations of the implications of deformable beds for process and form development are also being attempted. Finally, we are reassessing long-held beliefs about the significance of glacial action in landform development and sediment production. As we head towards the twenty-first century, glacial geomorphology will advance through the use of three-dimensional numerical models that in-clude ice flow, basal sliding (with explicit consideration of deformable beds), erosion and deposition processes, and un-derlying material characteristics. These models will be used to address form evolution and test process models, and will include both the temporal and spatial aspects of form development.
eBook - PDFGlacial Geology
An Introduction for Engineers and Earth Scientists
- N. Eyles(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
CHAPTER 5 Landforms and Sediments Resulting From Former Periglacial Climates N. Eylesand M. A. Paul INTRODUCTION Large tracts of the mid-latitudes south of the limit of glaciation (Fig. 1.1) are recognized as containing relict landscapes and soils resulting from former cold, periglacial climates. The purpose of this chapter is to provide a check list of sediments (engineering soils) and ground conditions of particular significance to applied studies. The general distribution of many of these features in mid-latitude areas such as Britain and North American can be depicted and their typical geometries identified at the scale of individual site investigations. The term periglacial is used elsewhere in this chapter as an umbrella-term 'for a wide variety of non-glacial processes and features of cold climates characterized by intense frost action regardless of age or proximity to glaciers' (Washburn, 1980). This is an important statement for it should be noted that the meaning of periglacial, as used elsewhere in the literature, is ambiguous. In some cases it is reserved solely for those conditions where permanently frozen ground (permafrost) is present. The term is also employed to describe a fringing zone around modern or Pleistocene ice caps. Similarly, reference to a 'periglacial climate' is unsatisfactory unless a particular climate is specified for there is a wide range of periglacial conditions with latitude and altitude. Periglacial environments range between the extremes of dry continental interiors with excessive seasonal extremes of temperature, to mountain zones in the mid and low latitudes where diurnal temperature changes are more marked and where mechanical break-up of rock masses by freeze-thaw cycles is at an optimum. It must also be pointed out that many soils and landforms identified as 'periglacial'form under conditions other than those of cold climates per se.
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