Periglacial Landscapes

11 Key excerpts on "Periglacial Landscapes"

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  Southern African Geomorphology

  Recent Trends and New Directions

  • Holmes, Peter, Meadows, Michael(Authors)
  • 2013(Publication Date)
  • UJ Press

    (Publisher)

  Periglacial and Glacial Geomorphology 9 233 1. Introduction The geomorphology of cold regions receives wide international attention from researchers, particularly in the context of past and future global environmental change (Haeberli and Beniston, 1998; IPCC, 2007). The term periglacial reflects a complex set of environmental interactions, but is used here to refer to a “wide range of cold, non-glacial conditions, regardless of their proximity to a glacier, either in time or space” (French, 1996:3), and is generally defined as “the sub-discipline of geomorphology concerned with cold non-glacial landforms” (French, 2007:5). The effectiveness of periglacial processes and landform development is controlled by many environmental factors including the nature of earth materials, available ground moisture and the intensity, duration and cyclic pattern of ground (soil or rock) temperatures passing below 0 °C. Areas with less severe frost action, such as in the mountains of southern Africa, are sometimes referred to as marginal periglacial or subperiglacial zones (e.g. Lewis, 1988a; Hanvey and Marker, 1992; Hall, 1992; Boelhouwers, 1994). Such areas typically experience diurnal or seasonal ground freeze. However, high latitude and high alpine regions where mean annual temperatures are usually below 0 °C may experience more severe frost action associated with permanently frozen ground, known as permafrost, which is ground that remains at or below 0 °C for at least two years (Harris et al., 1988). The landscapes reflecting present-day glacierisation and past glaciation are probably the most readily visible element of cold climate environments at a global scale. Glaciers and ice sheets currently cover around 10% of the Earth’s surface (~16 million km 2 ), but have covered over 30% during recent geological time.

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  Geomorphology

  The Mechanics and Chemistry of Landscapes

  • Robert S. Anderson, Suzanne P. Anderson(Authors)
  • 2010(Publication Date)
  • Cambridge University Press

    (Publisher)

  C H A P T E R 9 Periglacial processes and forms In the bleak midwinter, Frosty wind made moan, Earth stood hard as iron, Water like a stone . . . Christina Rossetti 270 The actions of frost and freezing temperatures produce unique landscapes shaped by frost heave and by soils that alternate between solid and semi-liquid state. As much of the land surface is either currently subject to freezing conditions, or has been shaped by freezing conditions in the past, the study of periglacial processes is relevant to much of the Earth’s surface. At present, mean annual temperatures are below 0 C for 35% of the terrestrial land surface. During past glaciations, periglacial processes operated over even greater areas of the earth. The word “periglacial” was first coined by a Polish geomorphologist (Lozinski, 1909 ) to describe Pleistocene-age features found in present-day Romania beyond the margin of the former Fennoscandian ice sheet. Today, however, the term periglacial describes non-glacial freeze–thaw processes in any setting. Hence, periglacial processes and landforms are not restricted to glacier or ice sheet margins. In periglacial environments, the phase change between water and ice can drive processes not found elsewhere. Periglacial processes are active today in alpine environments, in Siberia, in Tibet, and in vast tracts of Alaska and Canada. In this chapter The Arctic coastal plain in Alaska is patterned by ice wedge polygons in many areas, and dotted with innumerable lakes each summer. In winter, this landscape will resemble the imagery of Rossetti’s mid-nineteenth century carol (photograph by R. S. Anderson). 271 Freezing and thawing brings profound change to regolith materials, with important geomorphic conse-quences. The near surface undergoes annual cycles of freezing and thawing in which the water content, soil strength and bulk density of the soil change dramatic-ally.

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  Introduction to Process Geomorphology

  • Vijay K. Sharma(Author)
  • 2010(Publication Date)
  • CRC Press

    (Publisher)

  209 8 Periglacial Processes and Landforms Lozinski first used the term periglacial in 1909 to explain the distribution of frost-shattered debris about the cold ice-free margins of Pleistocene glaciers (Embleton and King, 1968). As frost activity is not exclusive to the proximity of either former or present-day glaciers, the term periglacial nowadays is used for cold region pro-cesses and their landforms (Price, 1972; Washburn, 1979; Thorn, 1992). Washburn (1979) adopted the term geocryology for processes and landforms of cold environ-ments, but periglacial term has come to stay in the literature, and is widely used for the purpose. IDENTIFICATION A periglacial environment is characteristic of subfreezing air temperature and a fro-zen ground to certain depth in the subsoil. This relationship between the air tempera-ture and frozen ground is central to the identification of a periglacial environment. Peltier (1950) defined a periglacial environment by a mean annual air temperature between −15 and −1°C and a mean annual precipitation of 125 to 1400 mm, mostly in the subarctic zone of tundra vegetation. Periglacial regions have also been identi-fied with a subfreezing air temperature for at least two consecutive summers and the intervening winter season (Brown and Kupsch, 1974), and with a below freezing subsoil temperature for two consecutive years (Washburn, 1979). Observations, how-ever, suggest that even a slight snow cover effectively insulates the ground beneath from the effect of air temperature fluctuation (Harris, 1974; Embleton, 1980; Harris, 1982; Harris and Brown, 1982; Ødegård et al., 1995; Carey and Ming-ko, 1998). Therefore, periglacial regions are simply identified with perennially and seasonally frozen ground characteristic of a certain magnitude of subfreezing mean annual tem-perature range.

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  Global Geomorphology

  • Michael A. Summerfield(Author)
  • 2014(Publication Date)
  • Routledge

    (Publisher)

  12 Periglacial processes and landforms DOI: 10.4324/9781315841182-12 12.1 The periglacial environment In the high latitude regions of the northern and southern hemispheres, and in some areas at high elevation elsewhere, prevailing temperatures are so low that the ground remains frozen for much, or all, of the year. In such environments the effects of repeated freezing and thawing and the growth of ice masses in the ground are so pervasive that they give rise to a characteristic range of landforms which merit special consideration. This is the realm of periglacial processes and landforms. Although their present extent is impressive, the Pleistocene saw the extension of periglacial conditions well into midlatitudes as the ice sheets of the northern hemisphere advanced southwards. Thus large areas now experiencing comparatively mild climates retain evidence in the form of relict periglacial landforms of much colder conditions as recently as 15 ka bp. Many high latitude regions today have acquired considerable economic and strategic significance and this has served to focus attention on the special characteristics of their landforms. The term ‘periglacial’ was introduced in 1909 by the Polish scientist Walery von Lozinski to describe the landforms and processes occurring around the margins of the great Pleistocene ice sheets. Subsequently it was applied more broadly to encompass those processes and landforms (regardless of age) associated with very cold climates in areas not permanently covered with snow or ice (and in many cases located far from glaciers or ice sheets). Such areas of extreme cold are commonly underlain by permanently frozen ground, or permafrost, and because many landforms characteristic of these regions owe their existence to permafrost its presence is regarded by some as a prerequisite for the action of periglacial processes

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  Geomorphology: 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)

  This is an areal concept, which comprises all studies on geomorphic processes and land-forms in a special zone or belt. It is accepted, even if Washburn, the grand old man of peri-glacial geomorphology describes the perigla-cial concept in general as sufficiently broad and unprecise to defy (climatic) quantifica-tion (Washburn, 1979, p. 2). For Washburn (1979,p.4), PERIGLACIAL GEOMORPHOLOGY IN THE 21 ST CENTURY 143 the term periglacial designates primarily terrestrial, non-glacial processes and features of cold climates character-ized by intense frost action, regardless of age or proximity to glaciers. French (1987, p. 5) accepts this generally adopted definition as he writes: Periglacial geomorphology seeks to explain the geo-morphic processes and landforms of cold non-glaciated environments... There are two criteria which identify per-iglacial regions. These are ( 1 ) the existence of intense freezing and thawing of the ground, either on a seasonal or daily basis, and (2) the formation and preservation of perennially frozen ground or permafrost. This definition represents the same um-brella as the other definitions, even if the first critérium for identifying periglacial regions is extremely unprecise: The intensity of freezing and thawing can be given by the (daily or an-nual) number of freeze-thaw cycles related to ground or air temperatures, by the intensity of the freezing using mean minimum ground or air temperatures, etc. None of the given possi-bilities is really convincing as a general critérium. In a recent paper, Thorn (1992) tries to avoid these uncertainties, defines periglacial geomorphology as follows (Thorn, 1992, pp. 1,24): Periglacial geomorphology is that part of geomorphol-ogy which has as its primary object physically based ex-planations of the past, present, and future impacts of diurnal, seasonal, and perennial ground ice on landform initiation and development.

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  Glacial 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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  Periglacial Geomorphology

  • Colin K. Ballantyne(Author)
  • 2017(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  2 Periglacial Environments

  2.1 Introduction

  As outlined in Chapter 1 , the geographical extent of present‐day periglacial activity is not easily defined, but here we adopt the view that the present periglacial realm encompasses all unglacierized regions where frozen ground and/or freezing and thawing of the ground significantly influences landform development. The present operation of frost‐action processes and the distribution of resultant landforms thus define the extent of the periglacial domain. The driving influence on frost action is climate, which represents the primary control not only on the distribution of permafrost and the depth of seasonal ground freezing and thawing, but also on the frequency of ground‐level freeze‐thaw events, the depth of winter snowcover, the seasonal availability of liquid water in the upper levels of the ground, the runoff regime of rivers and the propensity for erosion and deposition of sediment by strong winds. At a more local level, however, the effects of climate on ground temperature and geomorphological processes are modulated by vegetation cover and substrate characteristics. This chapter sets the scene for analysis of the processes operating in periglacial environments by outlining the characteristics of periglacial climates and briefly summarizing those of soils and vegetation cover in cold environments.

  2.2 Periglacial Climates

  No single climatic parameter adequately defines the limit of periglacial climates, though French (2007) suggested that this can be approximated by a mean annual air temperature (MAAT) of +3 °C. This is a useful criterion that encompasses not only the polar, subpolar and high‐altitude regions of the Earth, but also areas of shallow seasonal ground freezing. Classification of periglacial climates is inevitably rather arbitrary, as boundaries between climatic zones are gradational, and even within particular areas there may be marked climatic variation relating to such factors as altitude, slope aspect and distance from the coast. French (2007) employed a fourfold classification of periglacial climates (high arctic, continental interiors, alpine and climates with low annual temperature range) and identified two areas (the Qinghai‐Tibet Plateau and Antarctica) that do not fall readily into any of his classes. A similar but modified approach is adopted here. Note that precipitation figures cited here and illustrated in Figures 2.3 –2.5

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  Geomorphology

  • Mateo Gutierrez(Author)
  • 2012(Publication Date)
  • CRC Press

    (Publisher)

  At present more than 10% of this territory is active thermokarst. 15.3 Applied geomorphology in periglacial regions 15.3.1 Introduction Periglacial processes operate in both alpine and high latitude environments. Both are fragile areas where human activity can cause significant disturbances (Ritter, 1986). Permafrost ground poses numerous problems not only for cartographers but also for engineers, builders, miners, oil and gas produc- ers, climate scientists, archeologists, and anyone interested in polar and alpine regions (Heginbottom, 2002). Geocryologi- cal engineering is the study of frozen ground and its impact on human life and activities (Yershov, 1998). During the last few decades many mountainous areas have come under significant pressure as a result of human activities. In developed countries, increasing tourism and other recreational activities are the primary cause of this pres- sure (David et al., 2009). In developing countries, increased soil use in marginal areas puts pressure on low areas. In some underdeveloped zones, tourism is beginning to be a problem. In addition, deforestation and overgrazing in mountainous areas can modify the activity of geomorphic processes. These factors and human activities have increased natural risks such as avalanches, soil erosion, landslides, flooding, etc. (Gerrard, 1990). In arctic and subarctic regions the principal problems of economic development center on freezing of the land surface (congelifraction and frost heaving) and thawing of permafrost. These circumstances have limited development in these areas; man has had to resolve these problems with numerous and novel technical solutions (Sudgen, 1982; Walker, 1986).

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  The Periglacial Environment

  • Hugh M. French(Author)
  • 2013(Publication Date)
  • Wiley

    (Publisher)

  In mid-latitudes, which currently experience temperate climates, the major problem is to identify the degree to which the effects of the Pleistocene cold climates have been eliminated. Often lithology is the important variable controlling the degree of preservation of periglacial landforms. Careful field investigation is required before the nature and magnitude of the periglacial legacy can be established. It is useful at this point to distinguish between the terms “proglacial” and “paraglacial,” and to relate the conditions implied by these terms to landscape modification. Paraglacial refers to the disequilibrium that occurs as one geomorphic environment moves from one equilibrium condition to another (Church and Ryder, 1972). In the case of the periglacial environment, the transition is usually to, or from, a glacial or temperate environment, the so-called glacial and interglacial periods of the Pleistocene. The proglacial environment, which refers specifically to ice-marginal conditions, is a periglacial environment in the original sense of Lozinski. If we bear these two concepts in mind, one can illustrate the temporal relationships that exist between the glacial, periglacial, and temperate landscapes (Figure 2.1). Whether or not it is correct to assume that glacial landscapes are relatively high energy and temperate latitude landscape are relatively low energy is open to question. However, this is not of fundamental concern at this point. What is more relevant to our discussion is the assumption that Periglacial Landscapes reflect a constant energy condition, or equilibrium. Equally debatable is whether or not such equilibrium characterizes periglacial environments today. For example, the classic periglacial terrain that was examined by participants on the XI International Geological Congress field trip to Svalbard in 1910 constitutes the recently ice-free margin of a heavily-glaciated and mountainous island that is currently undergoing isostatic rebound

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  Landscape Processes

  An Introduction to Geomorphology

  • Darrell and Valerie Weyman(Author)
  • 2020(Publication Date)
  • Routledge

    (Publisher)

  Chapter 4

  Glacial and Periglacial Landscapes

  In glacial areas of the world, much of the water in the landscape is frozen throughout the year. These areas (Fig. 2) include the mountain ranges of otherwise temperate zones and areas within the Arctic and Antarctic circles. Generally speaking, the normal form of ice in temperate zone mountain areas is the valley glacier—a river of ice flowing from the highland zones of ice accumulation to the warmer reaches of the surrounding lowlands. In the Polar regions, however, ice tends to accumulate as ice-sheets of great thickness and areal extent which melt as warmer water or lower latitudes are encountered.

  Although there are enormous differences of scale between these two major occurrences of ice, many of the denudational processes are similar. Consequently, this chapter will examine first the valley glacier system in some detail before looking briefly at ice-sheets. The end of the chapter also includes a section on periglacial landscapes which may be found in the areas of Northern Canada and Siberia adjacent to the ice-sheets but not actually covered by ice throughout the year.

  A.  Water and ice in a valley glacier

  Glaciers normally start as accumulations of ice in pre-existing river valleys. Glacier ice is produced by the compaction of snow, the density of snow being 0·1 g/cm3 and that of glacier ice being 0·9 g/cm3 . Once a sufficient thickness of ice has developed, the glacier will begin to move downslope under the influence of gravity. The complete valley glacier system will probably consist of a number of high-level tributaries feeding ice to a main valley glacier (Fig. 53A).

  A glacier can move downslope in several ways. In the mountains of temperate zones, the ice at the bottom of a glacier will melt owing to the pressure exerted by overlying ice, despite the fact that the temperature will be less than 0 °C (the ‘freezing point’ only at normal pressure). Under these conditions the glacier is able to slide over the rock surface on this thin layer of water. In very cold climates, it is possible that pressure is insufficient to overcome the low temperatures, and, consequently, the ice remains frozen to the underlying rock. When basal sliding does occur, however, the ice acts partly as a rigid block of material. Further movement can be created within this rigid block by faulting and sliding within the ice mass (where it moves over an obstruction, for example). The faulting produces crevasses which extend down into the ice from the surface of the glacier. To some extent, ice can also behave in a plastic form, that is it can deform,

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  Visualizing Physical Geography

  • Timothy Foresman, Alan H. Strahler(Authors)
  • 2012(Publication Date)
  • Wiley

    (Publisher)

  They are characterized by cold temperatures, low snowfall, and limited vegetation. • Permafrost is ground that is perennially below freezing. Permafrost is continuous in the highest latitudes, as shown on the map. In lower latitudes, discontinuous permafrost includes areas of unfrozen ground called taliks. Distribution of permafrost • Figure 14.12 • Above the permafrost is an active layer that undergoes a seasonal cycle of freezing and thawing. • Water that freezes in the ground is ground ice. Cycles of freezing and thawing of ground ice cause frost action including frost heaving and frost thrusting. In the process of gelifluction, saturated soil can flow slowly downhill on a bed of permafrost. • Ice wedges are a form of ground ice found in permafrost terrains. Freezing pockets of water in lake beds push up hills called pingos. • Patterned ground occurs when freeze–thaw cycles distrib- ute rocks into patterns. • When the permafrost thaws, the ground can collapse to form a landscape of shallow lakes and trenches called thermokarst. Increased permafrost thawing results from global warming as well as human development on permafrost terrain. • As shown in the photograph, glaciers can erode bedrock by removing fractured blocks and using embedded rock frag- ments to chip or grind the bedrock. They leave depositional landforms, constructed of glacial drift, when the ice melts. Glacial abrasion • Figure 14.6 Glacial Landforms 433 • Alpine glaciers erode and enlarge the heads of mountain valleys to form cirques, leaving peaks called horns and sharp ridges called arêtes. • 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.

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