Geography
Glacial Landforms
Glacial landforms are physical features created or influenced by the movement and melting of glaciers. These landforms include U-shaped valleys, cirques, moraines, and drumlins, among others. Glacial landforms are important in understanding past and present glacial activity and can provide valuable insights into the Earth's history and climate changes.
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12 Key excerpts on "Glacial 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- Charles Fletcher, Dan Gibson, Kevin Ansdell(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
Glaciers A glacier is a large, long-lasting river of ice that forms on land, undergoes internal deformation, and creates Glacial Landforms (FIGURE 17.1). Glaciers are made of compressed, recrystallized snow, usually carrying a large sediment load, which range in length and width from several hun- dred metres to hundreds of kilometres. Most glaciers are several thou- sand years old, but the glaciers covering Greenland and Antarctica have been in existence in one form or another for hundreds of thousands of years. Glaciers develop on land at high elevations (mountains) and high latitudes (the Arctic and Antarctic) above the snow line, the eleva- tion above which snow tends to accumulate from one year to the next rather than completely melting during the summer. Even mountains I n 1837, a young Swiss zoologist named Louis Agassiz (1807– 1873) used critical thinking to develop a radical new hypothesis. He suggested that northern Europe had once been covered by thick layers of ice, similar to those covering Greenland, during a pe- riod that he called the ice age. Having spent time walking among the many glaciers that fill the valleys of the Alps, Agassiz observed that these “rivers of ice” were in motion. He saw that their fronts advanced and retreated at various times and that they carried, locked within their icy grip, large amounts of bedrock, gravel, sand, and mud. He also observed glacial sediments deposited many kilometres from their source. Agassiz compared the glacial striations (linear gouges in bed- rock made by rocks suspended in glacial ice) exposed by retreating glaciers to identical gouges found in bedrock far from any ice. In fact, he was able to explain many aspects of northern European (and later North American) sedimentary geology and geomorphology (the study of landforms) that until then had no good scientific explanation. For instance, he pointed out that the deep valleys and sharp peaks and ridges of the high Alps were the result of glacial erosion.
eBook - PDF- James Petersen, Dorothy Sack, Robert Gabler, , James Petersen, James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
As the glaciers melted and the ice sheets retreated, a totally new terrain, vastly different from that of preglacial times, was exposed. Today, evidence of glaciation is found throughout the region. The most obvious glacially produced landforms are the thousands of lakes (including the Great Lakes), the knobby terrain, and moraine ridges. Moraines left by advancing and retreating tongue- shaped ice lobes that extended generally southward from the main continental ice sheet also influenced the shapes of the Great Lakes. The ice sheet, its deposits of sediment, and its meltwaters also created other, smaller-scale features. The glaciers left a jumbled mosaic of deposits from boulders through smaller gravel to sand, The Map ■ CONTINENTAL GLACIATION Map Interpretation Digital aerial image of the region near Jackson, Michigan 570 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 Michigan Center for Geographical Information Copyright 2022 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. 571 1 9 - 8 P E R I G L A C I A L L A N D S C A P E S Copyright 2022 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. Copyright 2022 Cengage Learning. All Rights Reserved.
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.
No longer available |Learn more- James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
As the glaciers melted and the ice sheets retreated, a totally new terrain, vastly different from that of preglacial times, was exposed. Today evidence of glaciation is found throughout the region. The most obvious glacially produced landforms are the thousands of lakes (including the Great Lakes), the knobby terrain, and moraine ridges. Moraines left by advancing and retreating tongue-shaped ice lobes that extended generally southward from the main continental ice sheet also influenced the shapes of the Great Lakes. The ice sheet, its deposits of sediment, and its meltwaters also created other, smaller-scale features. The glaciers left a jumbled The Map CONTINENTAL GLACIATION mosaic of deposits from boulders through smaller gravel to sand, silt, and clay that has produced a hilly and hummocky terrain. The overall relief is low, in part because of glacial erosion. Many landform features of continental glaciation are well illustrated on the Jackson, Michigan, 15∙ quadrangle map. This region has a humid continental climate. The summers are mild and pleasant. Excessively warm and humid air seldom reaches this area for more than a few days at a time. Instead, cool but pleasant evening temperatures tend to be the rule in summer. Winters, however, are long and often harsh. Snow can be abundant and on the ground continuously for many weeks or even months at a time. The annual temperature range is quite large; precipitation occurs year-round provided primarily by midlatitude cyclonic storms. Interpreting the Map 1. Describe the general topography of the map area. 2. What is the local relief? Why is it so difficult to find the exact highest and lowest points on this map? 3. Does the topography of this region indicate glacial erosion or glacial deposition? 4. Does the area appear to be well drained? What are the three main hydrographic features that indicate the drainage conditions? 5.
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 Geology
The Science of Earth
- Charles Fletcher(Author)
- 2017(Publication Date)
- Wiley(Publisher)
A rctic C ircle Siberia Arctic Ocean Bay of Bengal South China Sea Pacific Ocean Pacific Ocean Alaska Present coastline Land exposed by lowered sea levels Himalayas Borneo Sumatra China India Philippines (a) (b) Describe changes in the water cycle that occur during an ice age. LO 15.4 Compare and contrast depositional and erosional features formed by glaciers. Over the past 500,000 years or so, Earth’s history has been characterized by great swings in global climate, from extreme states of cold (ice ages) to warm periods called interglacials. Glacial Landforms Are Widespread and Attest to Past Episodes of Glaciation 471 sunlight than on south-facing slopes. Cirques may contain a small lake, called a tarn. These high-elevation lakes, often set in idyllic alpine meadows, are known for their water clarity and beauty. Where three or more cirques carve out opposite sides of a mountain, the resulting sharp peak is a horn. Two adja- cent valleys that are filled with glacial ice may carve a sharp ridgeline called an arête. These landscapes often include hanging valleys formed during the last ice age, when a glacier in a smaller tributary valley joined a larger glacier in the main valley. The tributary glacier would not have an opportunity to erode its base to the floor of the main valley, so when glacial ice melted, the floor of the tributary valley was left “hanging.” Spectacular waterfalls plunging to the floor of the main valley often mark hanging valleys. Depositional Features Glaciers transport sediment of all sizes (Figure 15.17), from huge boulders the size of buildings to tiny clay particles. They carry this material either on the surface of the ice or embedded within the body of the glacier.
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.
eBook - PDFGlacial Geology
An Introduction for Engineers and Earth Scientists
- N. Eyles(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
1.2 Glacial Landsystems A complex range and distribution of sediments result from glaciation. As a means of classifying and mapping sediment sequences and landforms at the margins of modern day glaciers, it has been possible to recognize a number of distinct 3 Ground engineering/construction task J Terrain evaluation and landsystem identification Desk top studies I Prediction of soils and stratigraphy —►Site investigation -►Earth material testing I —►Foundation design — Excavation Construction Completion, use of site Maintenance phase -Mapping/representation .►Rejection of site? 4 N. Eyles landsystems each having characteristic topography, subsurface conditions and sediments (Boulton and Paul, 1976). By the identification of the landforms and terrain type, the geometry and character of subsurface stratigraphies can be generalised for large areas. The value of this approach to applied projects in mid-latitude areas of former Quaternary glaciations lies in its use as a mapping tool and as a rapid guide to likely subsurface conditions. Ground conditions resulting from glaciation can be generalised into three landsystems. (i) subglacial (ii) supraglacial (iii) glaciated valley The subglacial and supraglacial landsystems (Figs. 1.3, 1.4, 1.5) are characteristic of glaciated lowlands where sediments and landforms were deposited by large ice sheets. Glaciated valley terrain, on the other hand, results where the bedrock relief is so marked, as in mountain and highland areas, that bedrock protrudes through the drift cover and, during glaciation, breaks up ice lobes into valley glaciers (Fig. 1.6). Finally, ground conditions and landforms resulting from periglacial, cold climate conditions may be superimposed on and modify to varying degrees the three landsystems described above. These periglacially-modified terrains predominate in a broad zone south of the limit of glaciation; the so-called 'zone of fossil periglacial landscapes'.
eBook - PDFPhysical Geography
Made Simple
- Richard H. Bryant(Author)
- 2013(Publication Date)
- Made Simple(Publisher)
Areas of mounds and depressions commonly associated with a stagnant glacier are referred to as kame-and-kettle topography. The main landform created by proglacial deposition is the outwash plain or sandur. When the material is confined to a valley, the term valley train is used. These features are buiit up by the constantly shifting meltwater streams, dumping the coarsest material at the proximal end near the glacier margin, Glacial and Periglaclal Landforms 67 and carrying fine material to the distal end of the plain or train. The retreat of a glacier may result in several outwash features being formed, each related to a recessional moraine. Where proglacial debris is deposited into a lake, a delta will form. The fine bottom-set material deposited in the middle of the lake may be varved. Each varve consists of a pair of laminations, a coarser one representing summer deposition, and a finer one being the result of the slow winter precipitation of the finest material in the lake. The counting of varves has been used as a method of dating events. Fig. 6,9. Formation of a kame terrace. Other Effects of Glaciation Drainage Diversion by Ice Glaciation has important effects on the landscape beyond the direct modi-fications created by ice erosion and deposition. One example is that glaciation frequently disrupts pre-existing drainage lines, initiating a new pattern persist-ing after the ice has disappeared. Two well-documented instances occur in England. In the Midlands, what is now the Coventry/Warwick area was formerly drained by the headwaters of the River Soar, flowing into the Trent south of Nottingham. During glaciation, the valleys of the Soar and Trent were occupied by ice advancing from the north. At the same time, ice advanced from the Welsh mountains into the Vale of Evesham and combined with northern ice to pond up a large proglacial lake covering much of the Midlands.
eBook - PDFModern and Past Glacial Environments
Revised Student Edition
- John Menzies(Author)
- 2002(Publication Date)
- Butterworth-Heinemann(Publisher)
279 9 SEDIMENTS AND LANDFORMS OF MODERN PROGLACIAL TERRESTRIAL ENVIRONMENTS J. Maizels 9.1. DISTINCTIVENESS OF PROGLACIAL ENVIRONMENTS Proglacial environments lie at and beyond the ice margin. Sediments and landforms in proglacial envir-onments are dominated by meltwater and sediment derived from the ice mass itself The physical characteristics of proglacial environments are there-fore largely dependent on extraneous controls, affect-ing input of water and sediment to the system from beyond its boundaries, and reflect the nature of those water and sediment inputs, the volume, sources and character of the inputs and the pathways and rates of transfer through the system (Fig. 9.1) (Brodzikowski and van Loon, 1991). 9.1.1. Nature of Meltwater Inputs Meltwater inputs to proglacial environments are characterized by large-scale regular and irregular variability in runoff magnitude. Regular variations reflect seasonal and diurnal ablation cycles and responses to periods of glacier advance (positive mass balance) or retreat (negative mass balance). In most climatic zones, discharge fluctuations closely follow the annual temperature curve, with little or no flow occurring during winter. Four meltwater runoff peri-ods have been identified following the winter low-flow period (Sharp et al. , 1998): (1) spring meltwater flows occur in relation to break-up of river ice, while up to 25 per cent of meltwater produced is retained as superimposed ice, in snow and slush areas, and in ice capillaries and channels. Runoff amounts are much lower than expected because of this storage effect; (2) by early to mid-summer, rising temperatures lead to a rapid rise in snow melt followed by ice melt.
eBook - PDFGeomorphology
The Mechanics and Chemistry of Landscapes
- Robert S. Anderson, Suzanne P. Anderson(Authors)
- 2010(Publication Date)
- Cambridge University Press(Publisher)
The total debris discharge depends on both local slope and debris concentration. The moraine widens beyond the margins of the debris-rich septum through time. The moraine crest is convex, while the side slopes beyond the debris-rich ice septum are straight. Glaciers and glacial geology 260 evidence of the hydrologic and glaciological condi-tions during which they formed. The most extensive systems of eskers were formed beneath the continen-tal scale ice sheets. One of the most striking features of eskers is that they do not obey the contours of the landscape on which they currently rest. This could be explained in two ways. The first is that these conduits in which the gravels were initially deposited were englacial rather than subglacial conduits, and were simply laid down over the landscape as the glacier retreated. The second is that they are indeed subglacial, and that something inherent in the subglacial hydrologic system allows water to flow uphill. Sounds outra-geous, but this is the most likely. Arguments against the englacial explanation include the fact that the gravel deposits have intact stratigraphy that is not deformed by such a superposition on uneven ground. Most importantly, however, the apparent uphill flow of subglacial water, the details of where this uphill flow occurs, and the style of deposition in the various divides, can all be explained. We are very used to thinking about water responding only to topographic gradients, as it does when running in open channel flow on the surface of the Earth. But eskers represent flow in closed conduits – pipes – beneath the glacier. Just as water in a hose can be made to flow upward by water pressure gradients, so too is the flow in the conduits dictated by horizontal gradients in pressure, running down-gradient. The pressure field is governed not only by the bed topography, but also by the ice thickness profile, which involves both the ice surface and the bed profiles.
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