Geography
Glacial Processes
Glacial processes refer to the various mechanisms through which glaciers shape the Earth's surface. These processes include erosion, transportation, and deposition of sediments, as well as the formation of landforms such as moraines, drumlins, and eskers. Glacial processes are driven by the movement and melting of ice, and they play a significant role in shaping landscapes in polar and high-altitude regions.
Written by Perlego with AI-assistance
Related key terms
1 of 5
11 Key excerpts on "Glacial Processes"
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 - PDF- Alan F. Arbogast(Author)
- 2017(Publication Date)
- Wiley(Publisher)
387 CHAPTER 17 CHAPTER PREVIEW Development of a Glacier The Glacial Mass Budget Types of Glaciers Glaciers in the Cascade Mountains Glacial Landforms Depositional Glacial Landforms History of Glaciation on Earth Probable Human Impact on Glaciers Glaciers and Climate Change PeriGlacial Processes and Landscapes Glacial Geomorphology: Processes and Landforms The preceding chapter focused on the processes and landforms associ- ated with water that flows across the surface in rivers and streams. Now it is time to examine the character of flowing ice and the landforms that result from this movement. About 77% of the freshwater on land is stored as ice. Although it may not seem possible, this form of water moves as a glacier if it becomes sufficiently thick to flow under its own weight. Like streams, these rivers of ice can also shape the landscape in predictable ways through erosion and deposition. At the present time, ice covers about 11% of the Earth’s land surface. As recently as about 18,000 years ago, however, glaciers covered about 30% of the landmasses, including much of North America and Europe. As the climate warmed in the late Pleistocene and early Holocene, these giant ice sheets melted, and new landscapes created by Glacial Processes were uncovered. If you live in Canada or any of the northern states such as Wisconsin, Michigan, New York, Washington, or Illinois, your home may very well be built on deposits left by glaciers. Getty Images Flowing ice has had a huge impact on Earth throughout history. Although glaciers such as these in the Swiss Alps move slowly, they have tremendous power and are capable of eroding and depositing prodi- gious quantities of sediment. Much of the landscape seen here has been shaped in this way. This chapter focuses on Glacial Processes and the landforms that result from flowing ice. LEARNING OBJECTIVES 1. Describe how glaciers develop and the environmental conditions that are required.
eBook - ePub- (Author)
- 2015(Publication Date)
- Elsevier(Publisher)
Glasser and Bennett, 2004 ).12.8. Erosional process
Major processes of glacial erosion include: quarrying (also known as plucking), crushing abrasion, and mechanical and chemical erosion by glacial meltwater (Glasser and Bennett, 2004 ; Gregory, 2010 ). Glacial erosion creates a suite of landforms that are frequently observed in areas formerly occupied by ice sheets and glaciers (Glasser and Bennett, 2004 ). Quarrying involves the fracturing or crushing of bedrock beneath the glacier; and the entrainment of this fractured or crushed rock (Glasser and Bennett, 2004 ). Fracturing of bedrock occurs where a glacier flowing over bedrock creates pressure differences in the underlying rock, causing stress fields that are commonly sufficient to induce rock fracture (Glasser and Bennett, 2004 ; Morland and Morris, 1977 ). Plucking is particularly effective where a glacier flows over rock. Pressure exerted at the base of the ice melts the ice, which can refreeze in cracks in the underlying bedrock. Removing the pressure permits water to refreeze to the glacier and plucking occurs. Crushing occurs when the pressure exerted by basal rock fragments crushes the bedrock surface. Crushing develops crescentic fractures called chattermarks, which indicate the direction of motion of the glacier. Abrasion involves the wearing down of rock surfaces by the grinding effect of rock fragments frozen into the base of glaciers. It occurs when bodies of subglacial sediment slide over bedrock (Glasser and Bennett, 2004 ), and produces smoothed bedrock surfaces that often exhibit parallel sets of scratches, called striations (1–10 mm diameter) and fine silt-sized particles (0.1 mm) known as rock flour (Fig. 12.6
eBook - PDF- E. Derbyshire(Author)
- 2019(Publication Date)
- Routledge(Publisher)
5 Cryonival and Glacial Processes Realization that an enormous area of the land surface of the earth has been overrun by glacier ice at least once and probably many times in very recent geological time, spread relatively quickly after the publication of Etudes sur les glaciers by Louis Agassiz in 1840. Despite many diversions created by poorly founded and sometimes fantastic arguments, the glacial theory was well established by the beginning of the present century, and some of the most perceptive observations had been made and the essential relationships between process and landform by way of sedimentological properties established by the 1930s. Further progress was inhibited by the need for a strpnger observational basis, especially in subglacial locations, and by the rudimentary state of glaciological theory. With the rapid rise of the science of glaciology in the 1950s and 1960s, glaciological theory overtook that of glacial geomorphology and sedimentology and it is only in the last two decades that work in the field has been tailored to formulation of general theories of glacial erosion and deposition. These theories have greatly stimulated field work and they themselves are currently being tested and refined in the light of this field research. These changes, amounting almost to a revolution in thinking in glacial geomorphology and sedimentology, have been brought about by many professional geologists and geomorphologists, but the work of W. V. Lewis and his associates in the 1950s (Lewis 1960) and of G. S. Boulton since 1968 have been fundamental. General application of these ideas and of recent glaciological theory to perennial problems of glacial landform genesis has been attempted in the book by D. E. Sugden and B.S. John (1976). Awareness of the nature and extent of the cryergic (frost) and nival (snow) processes dawned early but application of the knowledge to geomorphological problems was slow to develop.
eBook - PDFGeomorphological Processes
Studies in Physical Geography
- E Derbyshire, K. J. Gregory, J. R. Hails, K. J. Gregory(Authors)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
5 Cryonival and Glacial Processes Realization that an enormous area of the land surface of the earth has been overrun by glacier ice at least once and probably many times in very recent geological time, spread relatively quickly after the publication of tudes sur les glaciers by Louis Agassiz in 1840. Despite many diversions created by poorly founded and sometimes fantastic arguments, the glacial theory was well established by the beginning of the present century, and some of the most perceptive observations had been made and the essential relationships between process and landform by way of sedimentological properties established by the 1930s. Further progress was inhibited by the need for a stronger observational basis, especially in subglacial locations, and by the rudimentary state of glaciological theory. With the rapid rise of the science of glaciology in the 1950s and 1960s, glaciological theory overtook that of glacial geomorphology and sedimentology and it is only in the last two decades that work in the field has been tailored to formulation of general theories of glacial erosion and deposition. These theories have greatly stimulated field work and they themselves are currently being tested and refined in the light of this field research. These changes, amounting almost to a revolution in thinking in glacial geomorphology and sedimentology, have been brought about by many professional geologists and geomorphologists, but the work of W. V. Lewis and his associates in the 1950s (Lewis 1960) and of G. S.Boulton since 1968 have been fundamental. General application of these ideas and of recent glaciological theory to perennial problems of glacial landform genesis has been attempted in the book by D. E. Sugden and B. S. John (1976). Awareness of the nature and extent of the cryergic (frost) and nival (snow) processes dawned early but application of the knowledge to geomorphological problems was slow to develop.
eBook - PDF- Vijay K. Sharma(Author)
- 2010(Publication Date)
- CRC Press(Publisher)
171 7 Glacial Processes and Landforms In parts of North America, Europe, and Asia, massive glaciers periodically appeared in colder glacial and thawed in warmer interglacial phases of the Pleistocene climate. This ice of continental dimension reached a massive thickness of 3 km or more at places by slow accretion over thousands of years in glacial phases (Gates, 1976), but thawed rapidly in less than a decade in intervenient interglacial phases of the Pleistocene epoch (Lehman, 1997). These recurrent events eventually culminated in 10,000 years BP, bringing the 2-million-year-old Great Ice Age to a sudden end. The multiple glaciation has modeled the landscape beneath sliding glaciers and the yield of meltwater discharge beneath and beyond the vast expanse of glacier ice. GLACIERS Glaciers are a large mass of perennial ice. The ice comprises several centimetres across interlocked ice crystals of variable size and orientation. This ice begins as 0.02 to 0.08 density hexagonal-shaped snowflakes. The snowflakes progressively increase in density by compaction, melting, air expulsion and recrystallization pro-cesses, evolving 0.85 to 0.9 gm cm −3 density ice through intermediate stages of con-version to granular snow and firn. Massive glaciers that flow outward from their centres of ice accumulation are called ice sheets . Glaciers occupy some 11% of the earth’s land surface, but hold roughly 75% of its fresh water. T HERMAL P ROPERTIES OF G LACIERS The thermal gradient of the ice distinguishes temperate or warm-based and polar or cold-based glaciers as two fundamental types with several transitions in between. The thermal gradient , in general, is a function of the air temperature, thickness of the ice mass, heat conductivity of the ice, and geothermal heat escape through the ice.
eBook - PDF- David Huddart, Tim A. Stott(Authors)
- 2019(Publication Date)
- Wiley-Blackwell(Publisher)
This work hints at the potential for glaciovolcanic environments to be associated with more extensive glaciolacustrine sediment assemblages. The importance of Glacial Processes has been emphasized by Bennett et al. (2008) in an exploration of the glaciovolcanic sequences of the Brekknafjöll‐Jarlhettur ridge in central Iceland (Figure 20.74) adjacent to the east- ern margin of the Langjøkull ice cap, which not only contains a complex assemblage of glaciovolcanic products but is associated with deposits of glaciola- custrine diamict that are in places deformed to cre- ate large‐scale glaciotectonic structures. 605 Earth Environments, Second Edition. David Huddart and Tim A. Stott. © 2020 John Wiley & Sons Ltd. Published 2020 by John Wiley & Sons Ltd. Companion Website: www.wiley.com/go/huddart/earth-environments Pingo degradation and melting ice wedge polygons near Tuktoyaktuk, North West Territories, Canada. Photo: Emma Pike, Wikipedia Commons 21 PeriGlacial Processes and Landform‐Sediment Assemblages 606 21.1 Introduction to the Term ‘Periglacial’ ‘Periglacial’ is a term which has had many connota- tions since it was first used by Lozinski (1909, 1912). A periglacial zone was originally defined as periph- eral to Pleistocene glaciers and was cold, mountain- ous, proglacial, or ice‐marginal, sparsely vegetated and mid‐latitude in nature. Such a periglacial zone is a specific and limiting type of periglacial environ- ment, which is difficult to recognize in modern analogues today and not typical of the majority of present‐day periglacial environments. Nor was it necessarily typical of Pleistocene periglacial envi- ronment to the south of the large continental ice‐sheets either. The landscape was dominated by frost processes, but frost action also influences land- scapes that were not at the margins of Pleistocene glaciers. For this reason, a broader definition of ‘periglacial’ is needed.
eBook - PDF- Philip A. Allen(Author)
- 2009(Publication Date)
- Wiley-Blackwell(Publisher)
Glaciers erode their bases and sides by abrasion and by plucking of blocks, producing a range of erosional landforms. The debris carried by icc may be trans- ported on the glacier surface, within it, or at its base. The deposits are termed moraine and take on a great variety of forms depending on the precise mode of transport and deposition. The action of meltwater is very important in transferring glacial sediment to 11.1 Introduction: the cryosphere Snow and ice cover large proportions of polar regions and terrains at high elevations in all latitudes, comprising 14.9x 10 6 km 2 , about 10% of the Earth's land surface. Of this area of ice, the vast majority is found in the Antarctic ice sheet (Plate 11.1, facing p. 204), and to a lesser extent in the Greenland ice sheet. As a percentage, very little ice makes up the valley glaciers that characterize anum ber of the Earth's mountainous regions such as the European Alps, Alaska, North America, or the Himalayas of Asia (Table 11.1). We know, too, that during the relatively recent past in the Pleistocene, glaciers and ice sheets were far more extensive (Chapter 2). At 18000 BP, the area covered by ice is thought to have been as high as 30% of the Earth's land surface. This has profound significance for today's landscapes, since landforms in many regions are a legacy from a glacial past rather than reflecting present-day conditions. The glacial system receives inputs from precipi- tation in the form of snow, and mineral debris trom the erosion of the glacier bed and sides and from erosion of surrounding hillslopcs. The glacial system suffers losses caused by solar radiation inducing the tluvioglacial system. Meltwater discharges are typically highly concentrated in sediment, and spread their sediment load over braided and anastomosing plains known by the Icelandic term sandar.
eBook - PDF- Timothy Foresman, Alan H. Strahler(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
Here we can watch glaciers in action to learn how they move, erode, and deposit sediment to create their distinctive landforms. Glacial and Periglacial Landforms The Margerie Glacier, a tidewater glacier in Glacier Bay National Park, Alaska, heads high in the Fairweather Range near Mount Quincy Adams and flows into an arm of Glacier Bay. 425 CHAPTER OUTLINE Types of Glaciers 426 • Alpine Glaciers • Ice Sheets ■ Where Geographers Click: Monitoring the Wilkins Ice Shelf Glacial Processes 429 • Formation of Glaciers • Movement of Glaciers • Glacial Erosion and Deposition Glacial Landforms 433 • Landforms Made by Alpine Glaciers • Landforms Made by Ice Sheets PeriGlacial Processes and Landforms 440 • Permafrost • Ground Ice and Periglacial Landforms ■ What a Geographer Sees: Ice Wedges • Human Interactions with Periglacial Environments Global Climate and Glaciation 445 • History of Glaciation • Triggering the Ice Age • Cycles of Glaciation • Glaciation and Global Warming ■ Video Explorations: Antarctic Ice ✓ ✓ CHAPTER PLANNER ❑ Study the picture and read the opening story. ❑ Scan the Learning Objectives in each section: p. 426 ❑ p. 429 ❑ p. 433 ❑ p. 440 ❑ p. 445 ❑ ❑ Read the text and study all figures and visuals. Answer any questions. Analyze key features ❑ Geography InSight, p. 426 ❑ Where Geographers Click, p. 428 ❑ Process Diagram p. 434 ❑ p. 437 ❑ ❑ What a Geographer Sees, p. 442 ❑ Video Explorations, p. 449 ❑ Stop: Answer the Concept Checks before you go on. p. 429 ❑ p. 433 ❑ p. 439 ❑ p. 444 ❑ p. 449 ❑ End of chapter ❑ Review the Summary and Key Terms. ❑ Answer the Critical and Creative Thinking Questions. ❑ Answer What is happening in this picture? ❑ Complete the Self-Test and check your answers. 426CHAPTER14 GlacialandPeriglacialLandforms Types of Glaciers LEARNING OBJECTIVES 1. Describe thefeaturesandtypesofalpine glaciers.
eBook - PDF- Alan H. Strahler(Author)
- 2013(Publication Date)
- Wiley(Publisher)
This chapter is the also last in the group in which we reviewed landform- making agents and processes that operate on the surface of the continents, ranging from mass wasting to fluvial action, waves, wind, and glaciers. It is easier to distinguish among the wide variety and complexity of landforms by examining each agent in turn, as we have done here. This chapter also completes our presentation of physical geography, which has covered topics from weather and cli- mate to biogeography and landforms. By learning to observe and experience the world around you from this perspective, you can better understand and appreciate your environ- ment and the processes that are constantly shaping it. Human activity has changed the Earth in many ways over the last few millennia and our impact on it will continue to be felt, even more strongly, in the future. We –10 0 10 Difference in insolation, W/m 2 0 50 100 150 200 250 300 350 400 450 500 Thousands of years before present –20 20 65° N 17.30 The Milankovitch curve The vertical axis shows fluctuations in summer daily insolation at lat. 65° N for the last 500,000 years. These are calculated from math- ematical models of the change in Earth–Sun distance and change in axial tilt with time. The zero value represents the present value. According to the astro- nomical hypothesis, the timing of glaciations and interglaciations is determined by varia- tions in insolation pro- duced by minor cycles in the Earth ’s orbit and the Earth ’s axial rotation. In Review 587 I N REVIEW GLACI AL LANDFORMS AND THE I CE AGE ■ Global warming is causing an increase in the amount of snow accumulation on some ice sheets; it is also an agent of the melting and thinning of ice shelves and the edges of ice sheets. ■ Although the East Antarctic Ice Sheet is holding its own currently, the West Antarctic Ice Sheet is losing ice mass, as is the Greenland Ice Cap. These com- bined losses are contributing to sea-level rise.
eBook - PDFModern and Past Glacial Environments
Revised Student Edition
- John Menzies(Author)
- 2002(Publication Date)
- Butterworth-Heinemann(Publisher)
Glacial particle shape evolution demonstrates the enormous range of wear processes that impinge on any single particle over both temporal and spatial ranges and the common tendency for particle shapes from many sources and wear process combinations to exhibit equifinal shape geometries. Great caution must therefore be used in discriminating between different glacial environments solely upon particle shape and roundness. 6.6. GLACIOLOGICAL EFFECTS OF DEBRIS IN TRANSPORT 6.6.1. Rheological Effects of Englacial Debris In recent years it has become increasingly apparent that debris is not transported entirely passively by glacier ice. Rather, particles in transport significantly alter the deformational behaviour (rheology) of ice both directly (through the inclusion of undeformable rock and mineral grains within ice) and indirectly (through affecting ice crystal growth). Glacier ice deforms along glide planes parallel to the basal crystallographic plane. The presence of undeformable sediment within an aggregate of ice crystals has been shown experimentally to reduce the creep rate of ice even at low sediment concentrations (Nickling and Bennett, 1984). In heavily sediment-charged ice, friction caused by interparticle interactions stiffens ice. In marked contrast, borehole closure measure-ments from ice sheets show that sediment-charged ice deforms more easily than ‘clean ice’. Experiments to test the influence of englacial sediment on ice rheology have given quite different results from borehole observations. Nickling and Bennett (1984) found that ice attained a peak strength at a sediment concentration of 25 per cent by volume, with ice becoming more deformable at higher concentrations. No simple inverse relationship was found between debris content and creep rate. Englacial sediment indirectly affects ice rheology through its influence on ice crystal growth. Basal ice sequences usually have small crystals where sediment concentration is high.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
