Past Glacial Environments

John Menzies, Jaap van der Meer

• Publisher: Elsevier
• Year: 2017
• ISBN:
  9780081005255
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Geology & Earth Sciences

Past Glacial Environments, Second Edition, presents a revised and updated version of the very successful first edition of Menzies' book, covering a breadth of topics with a focus on the recognition and analysis of former glacial environments, including the pre-Quaternary glaciations.

The book is made up of chapters written by various geological experts from across the world, with the editor's expertise and experience bringing the chapters together. This new and updated volume includes at least 45% new material, along with five new chapters that include a section on techniques and methods.

Additionally, this new edition is presented in full color and features a large collection of photographs, line diagrams, and tables with examples of glacial environments and landscapes that are drawn from a worldwide perspective.

Informative knowledge boxes and case studies are included, helping users better understand critical issues and ideas.

• Provides the most complete reference concerning the study of glacial processes and their geological, sedimentological, and geomorphological products
• Comprised of chapters written by various geological experts from across the world
• Includes specific case studies to alert readers to important ideas and issues
• Uses text boxes throughout to explain key concepts from glacial literature
• Presents full color photographs, line diagrams, and tables throughout

Chapter 1

Introduction

J. Menzies¹ and Jaap J.M. van der Meer², ¹Brock University, St. Catharines, ON, Canada, ²Queen Mary, University of London, London, United Kingdom

At this time, in the second decade of the 21st century, global warming is ongoing. Climate change is more rapid than previously thought. Catastrophic storms and significant climatic events are evermore vast and costly. Social, economic and political changes to human societies on Earth are imminent and, in some cases, already ongoing due to global warming events and their repercussions. Sea level is rising at unprecedented rates. Glaciers are shrinking rapidly. If there ever was a reason among many to study past glacial environments it has never been more imperative than now. Furthermore, as glaciers have been extensively monitored and mapped over the last century, the glacier beds currently exposed by ice retreat can be directly linked to glacier properties, interpreting past glacier environments is very opportune.

Valley glaciers, ice sheets, ice caps, ice fields and ice shelves are the very ‘pulse’ by which climate change and thus global warming can be demonstrated and subtly directly related. As ice masses advance and retreat, these movements can be reliably correlated with climate change over time. In order that such ice masses move, an understanding of ice physics is essential. Movement of all ice masses occurs at the complex basal interface between ice and the underlying bed. As such the bed, its composition, topography, thermal characteristics and behaviour under strain by moving ice are central. Access to the basal interface under active present-day ice masses is by default a dangerous and risky endeavour. Various novel techniques of data acquisition are now tested. However, the base of any ice mass is exposed on the retreat of the ice thus providing a superb laboratory. Much of this textbook explores these now-exposed basal interfaces and the sediments and landforms so exposed.

It is essential in understanding these sediments and landforms to have a clear and precise grasp of how these glacial sediments form today and formed in Quaternary and pre-Quaternary environments. Glacial environments once thought to be unique to modern ice masses and those deposited in the Quaternary (The Ice Age) (Chapter 4) are now recognized to have been formed in most geological periods (other than the Jurassic) (Fig. 1.1); (Chapters 2, 3). In effect our planet is characteristically a ‘glacial planet’, where most often global glaciation events covering over 60% of the earth have occurred repeatedly (Chapters 2, 3, 4). Under ‘Snowball Earth’ conditions in the Neoproterozoic, e.g., the earth appears to have been totally ice-covered (Arnaud et al., 2011; Le Heron et al., 2013). Such is the all-pervading presence of glacial sediments that they can be found on every continent. Because the earth has been repeatedly glaciated and thus suffered both icehouse and greenhouse conditions, much can be learned of these events that have direct and immediate bearing on today’s rapidly advancing greenhouse conditions and in the near future. The predicative value of science has never more been critical to understanding how our planet will change and the tempo of that change by understanding past glacial environments and conditions.

Figure 1.1 Palaeogeography of global glaciations from the Neoproterozoic until the present day. Note ‘Snowball Earth’ glaciations in the Neoproterozoic covered 100% of the Earth. During subsequent glaciations only partial cover of the Earth occurred (approximately 60% Earth coverage that included continents and continental shelves). Adapted from http://www.snowballearth.org/ Slide 1.3.

Glaciers and ice sheets have an enormous effect upon all aspects of earth systems. At present, the complexities of ice dynamics and the relevant variables and influences they have on ice mass balance, and on the specific reasons for ice front and meltwater discharge fluctuations, remain poorly understood. The processes of ice basal movement, basal interfaces between ice and the subjacent bed whether deforming or not, thermally temperate or polar or more likely polythermal states and the intricate relationship between ice motion and subglacial hydrology continue to be investigated (Chapter 5). The key to ice movement whether in surge (fast ice) or ‘normal’ motion remains unanswered. Modern glaciers can be viewed as active analogues of past glaciers and ice sheets (Chapters 6, 7). Modelling of modern ice masses and mass balance studies advance our knowledge in explaining past global ice sheet development and expansion (Chapter 18). The diverse subenvironments of glaciers, both on land and subaquatically, provide an active field laboratory for studying present glacial sedimentological processes that can be employed to understand and interpret past glacial environments (Chapters 8–15). However, in utilizing modern ice masses as analogues of the past, care must be exercised, since past ice masses may have been significantly different in many critical aspects.

1.1 Impact of Past Glacial Environments on Planet Earth

The Earth is essentially a glacial planet (icehouse) punctuated by periods of ameliorative conditions (greenhouse) similar to or occasionally warmer than the period we live in today. Almost all aspects of life on Earth are influenced to a greater or lesser extent by the impact and persisting effects of glaciation. The distribution of plants, animals, early humans, soil types and coastal morphology are a few examples of the direct influence of global glaciation. Even in the tropics, where climatic conditions have remained relatively unchanged for at least the past 15 million years, the northern and southern boundaries on land and the repeated changes in ocean sea level have resulted in climatic and biogeographic changes all as a response, however imperceptible and subtle, to global glaciation. The dire impact of global warming and consequent climate change are enormous to comprehend (Hansen et al., 2016). The effect of such changes on human society, in all aspects, are truly major from the slight changes in a very few locations to cataclysmic changes in most parts of the world (see chapters: Geographic Information Systems and Glacial Environments (Chapter 14); and Soils and Palaeosols in Glacial Environments (Chapter 17)). Political, economic and societal changes of unheralded levels have never really been contemplated before by global community. The effect of ice sheets and glaciers, particularly on global habitats and earth systems, on sea level changes (Chapter 16), on the fluctuations of desert boundaries and discontinuous and continuous permafrost zones fast disappearing, e.g., can be viewed at two levels of impact: first, their influence upon humans and habitats within their immediate locality, and second, on their much more pervasive influence on all global habitats owing to the effect of modern ice masses on global climate and sea level (Church et al., 2013) (Chapters 8, 9, 10, 11, 12, 13). The effect of ice masses in the immediate proximity to humans is well documented (Hambrey and Alean, 1992; Vrba, 1995; Jansen et al., 2007; Change IPCC, 2013; IPCC, 2014) in terms, e.g., of meltwater outbursts and rapid ice advances resulting in the loss of pasture lands, property and, in some cases, human fatality. These detrimental aspects, of course, need to be balanced with the beneficial resources of water for hydroelectric projects, irrigation and fresh domestic water supplies. Less obvious, but actively researched today, is the more insidious and pervasive influence of present-day ice masses on global climate and oceanic currents (Böning et al., 2008; Purkey and Johnson, 2010; Rignot et al., 2011). As predictions of global warming increase, so knowledge of modern glacial conditions needs to be amplified if we are to cope with and predict sea level rise in the coming century when this knowledge will become acutely significant (Willis et al., 2010; Hansen et al., 2016). Considering the enormity of this influence, the relevance today of past glacial environments and their sediments and landforms cannot be undervalued. It is more than likely that the Earth will experience further global glaciations. Human activities, especially over the past 200 years, have exacerbated and accelerated some of the complex oceanic/atmospheric and solar forcing interrelationships but to what extent remains unknown. To be able to predict and be prepared for future global change, a profound knowledge of past glacial environments must be gleaned from the vast record that past glaciations have left behind. Related to potential sea level rise resulting from ice sheet melting in Greenland and Antarctica is the question of future ice sheet stability (Chapter 7). If these ice sheets melt at an increased rate vast plumes of cold fresh water may be injected into the polar oceans affecting oceanic habitats, currents, surface ocean water temperatures (e.g., El Niño–Southern Oscillation events) and, consequently, global weather patterns (Moon et al., 2015; Overland et al., 2015; Stott et al., 2016).

A further aspect of glacial environments is in providing analogues to past glacial conditions as a key to understanding present and future glacial processes. By studying present-day glacial environments and sedimentological processes, considerable knowledge can be gleaned as to how sediments of past glacial events have been derived, transported, and finally deposited both on land and in water (Chapters 8, 9, 10). Pleistocene glacial sediments cover today at least 30% of the Earth’s continental landmasses, and an even greater area must be included when Pre-Pleistocene sediments ranging over vast areas of India, Australia, Africa and South America are considered (Hambrey and Harland, 1981; Arnaud et al., 2011; Young, 2013; Fleming et al., 2016; Spence et al., 2016) (Chapters 7, 11). These sediments affect almost every aspect of human life from establishing foundations and footings for buildings, windmills, roads and runways; the nutrient content of soils; the nature of groundwater supplies; to the potential soil routes for contaminant waste disposal and the location of landfill sites (Chapters 12, 13). These few examples illustrate the vital need to understand glacial processes ongoing in glacial environments (De Mulder and Hageman, 1989; Hay, 2016). Until relatively recently this figure of 30% for Pleistocene sediments was accepted yet, today, perhaps approximately 60% would be a more accurate figure if glaciomarine sediments are included. These thick sediments lie over the ocean floors covering enormous parts of the northern and southern areas of the Atlantic and Pacific Oceans (Kennicutt et al., 2014; Simard et al., 2015). The impact of glaciomarine sediments on land-based habitats is certainly limited, affecting only fisheries to a little-known degree, but if future utilization of oceanic basins occurs the influence of these vast areas of glacial sediments may become increasingly meaningful.

1.1.1 Recognition of ‘Ice Ages’

From medieval times there have been innumerable explanations of features that we now recognize as glacial forms, such as erratic boulders viewed as the putting stones of giants, potholes as devils’ punch bowls and other demonic interpretations for glacial phenomena. Where and when precisely a glacial explanation of many of these features was first enunciated is difficult to determine, but by the mid-18th century in Scandinavia, Germany, Iceland and Switzerland, several individuals had begun to suggest that glaciers had been more extensive in the past (Nilsson, 1983; Dawson, 2013; Montañez and Poulsen, 2013; Rapp, 2013). In the 19th century, Charpentier, Agassiz, Buckland and Esmark, e.g., had begun to realize that large areas of Europe had been glaciated by vast ice sheets and thus the concept of the ‘ice age’ was proposed. This suggestion was not established, however, in many parts of Europe and North America until the late 1800s, and even up to the 1920s there were individuals who still questioned the very idea of an i...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Glacier Ice
• List of Contributors
• Preface
• Chapter 1. Introduction
• Part I: The Prequaternary
• Part II: The Quaternary
• Part III: Glacial Processes
• Part IV: Techniques and Methods
• Part V: Problems and Perspective
• Index