Fundamentals of the Physical Environment

Fourth Edition

Peter Smithson, Ken Addison, Ken Atkinson

• Publisher: Routledge
• Year: 2013
• ISBN:
  9781135090104
• Edition: 4
• Topic: Biological Sciences
• Subtopic: Ecosystems & Habitats
• Index: Biological Sciences

Fundamentals of the Physical Environment has established itself as a well-respected core introductory book for students of physical geography and the environmental sciences. Taking a systems approach, it demonstrates how the various factors operating at Earth's surface can and do interact, and how landscape can be used to decipher them. The nature of the earth, its atmosphere and its oceans, the main processes of geomorphology and key elements of ecosystems are also all explained. The final section on specific environments usefully sets in context the physical processes and human impacts.

This fourth edition has been extensively revised to incorporate current thinking and knowledge and includes:

• a new section on the history and study of physical geography
• an updated and strengthened chapter on climate change (9) and a strengthened section on the work of the wind
• a revised chapter (15) on crysosphere systems - glaciers, ice and permafrost
• a new chapter (23) on the principles of environmental reconstruction
• a new joint chapter (24) on polar and alpine environments
• a key new joint chapter (28) on current environmental change and future environments
• new material on the Earth System and cycling of carbon and nutrients
• themed boxes highlighting processes, systems, applications, new developments and human impacts
• a support website at www.routledge.com/textbooks/9780415395168 with discussion and essay questions, chapter summaries and extended case studies.

Clearly written, well-structured and with over 450 informative colour diagrams and 150 colour photographs, this text provides students with the necessary grounding in fundamental processes whilst linking these to their impact on human society and their application to the science of the environment.

Introduction

We start the first part of our book with some of the approaches that have been made in the study of physical geography. Compared to some disciplines, physical geography is relatively new, having emerged from geology and physiography in the late nineteenth century. As Geography Departments became established in more British universities in the early twentieth century, so interest in the subject increased and moved away from its background of geology. Instead there was a greater awareness of the interaction between the different parts of the Earth system, though initially much effort was spent in describing the features. Early studies concentrated on the description of the physical features of the landscape such as cirques, arêtes, oxbow lakes, landslides and spits, to choose examples from a range of geomorphological features as we would now call them. Similarly in climatology, Köppen developed a descriptive scheme to identify the range of climates that were observed across Earth’s surface.

Once a subject has been fully described the next stage is to develop an understanding of how and why particular features have been formed and increasingly studies in physical geography have moved towards an examination of the processes involved in their formation. Associated with this movement towards process studies, there has been a shift in the way we approach our subject matter with greater emphasis on the total system that is involved in the formation and development of a particular environment. This is why we start our first chapter with a case study of one small area and treat it as an environmental system. In this way we hope to show how what we see in the landscape is the product of a variety of separate and interacting systems. Any example could have been chosen, so it could be a useful exercise to take an area known to you and, once you have gained some understanding of the processes involved, produce a similar study of the environmental systems of that area. Comparisons could then be made to see what differences exist and, of course, why this should be. By these methods it is possible to manage the physical environment more sympathetically and to respond to foreseen and unforeseen environmental changes.

The study of physical geography also involves practical aspects as well as textbook learning. Geography has a strong tradition of field work and we would like to stress the importance of “hands-on” experience of learning about our environment. Field work and field experiments can allow greater insight into the operations of our environmental systems as shown in Chapter 1. Increasingly too, the data and material obtained from such field experiments can be used in laboratory analysis to quantify the processes involved. As computers have become more powerful too, increasingly realistic models of the environment can be built to allow prediction as well as observing what appears to be happening in our various systems.

One of the most important aspects of our environmental system is energy. Energy can flow into and out of a system or be stored in a variety of forms. Chapter 2 concentrates on examining the different forms of energy and their nature. Some are more important in the environmental system than others so we do not treat them equally but concentrate on those forms which are of greatest significance. The sun is our main source of energy and helps to drive many of the energy flows that take place on a wide range of scales from global to local. Without the presence of the sun and its energy we would be a dead planet. This chapter concludes with a discussion of local and regional energy transfers in different components of the environment. By studying these flows we hope to gain a better understanding of the processes and mechanisms that produce Earth’s environmental system.

Chapter One

The Physical Environment Scientific Concepts and Methods

1

Upper Wharfedale, North Yorkshire

Situated some 45 km north-west of the city of Leeds in northern England lies the village of Grassington near the river Wharfe. The Wharfe is one of a series of rivers rising in the Pennine uplands of northern England and flowing eastwards to the North Sea. Grassington forms a ‘gateway’ to Upper Wharfedale, a 17 km steep-sided valley. Upper Wharfedale has one prominent right-bank tributary, the river Skirfare, occupying Littondale; other tributaries to the river Wharfe are a series of short, steep-gradient streams or becks entering on the left bank (Plate 1.1). Wharfedale is one of the dales in the Yorkshire Dales National Park, and is attractive to geographers and tourists alike (Figure 1.1).

The attraction of Upper Wharfedale for visitors, as in all other dales in the National Park, lies in the unique assemblage of environmental elements which interact together to produce a landscape of great interest and beauty. Figure 1.2 shows how the four factors of (1) geology, (2) physiographic evolution, (3) climate and hydrology, and (4) ecological and anthropogenic history work together in this dale. By the word factor is meant a control which produces an effect. In physical geography it is recognized that these four controls act together in a complex manner to produce the totality of the physical environment. Another way of expressing this is to visualize the four controls as inputs into the total landscape system.

The geology refers to the physical and chemical nature of the solid rocks which underlie any part of Earth’s surface, together with associated structures such as faults and folds. It includes also unconsolidated sediments at the surface deposited by glaciers (till), rivers (alluvium) and slope-processes (colluvium or head). The physiographic evolution includes the present landforms of a region, their morphology (i.e. shape and size) and the manner in which they have been changed over time; the study of physiographic evolution is thus both spatial (i.e. of space) and temporal (i.e. of time). Climate and hydrology include the pattern of climatic elements (e.g. insolation, temperature, precipitation and wind) and the movement of water on or in Earth’s surface (i.e. the hydrological cycle). Ecological and anthropogenic history donate two influences of a biological nature; ecological controls focus on soils, vegetation (flora)and animals (fauna), whilst anthropogenic history includes the influences of human beings on all parts of the physical landscape, both now and in the past.

The geology plays a large part in forming this landscape (Figure 1.3). The rocks are horizontally bedded Upper Palaeozoic Carboniferous limestones and sandstones which have been deposited unconformably on Lower Palaeozoic Ordovician and Silurian rocks, and on Wensleydale Granite. The basal Carboniferous unit is about 360 m thick and comprises a series of limestones, the thickest being the Great Scar Limestone which outcrops prominently in Wharfedale and Littondale. Its name derives from the manner in which it weathers and erodes into terraces along bedding planes. Being well jointed, backwards retreat occurs by the successive fall of cube-shaped masses, thus retaining a vertical bare rock face, or ‘scar’. The Great Scar Limestone has been well studied, not least because of the striking variety of karst features to which it gives rise, both underground and on the surface (Waltham et al. 1997).

Figure 1.1 Relief and drainage of Upper Wharfedale, North Yorkshire.

Overlying the Carboniferous Limestone Series are about 230 m of strata of the Wensleydale Group (previously called the Yoredale Series) consisting of cyclical deposits of limestones, sandstones and shales. In turn the Wensleydale strata are overlain by about 40 m of Millstone Grit, a series of coarse sandstones which give the highest flat-topped peaks in the Yorkshire Dales, as on the eastern side of Upper Wharfedale at Buckden Pike (702 m) and Great Whernside (704 m).

Plate 1.1 The head of Upper Wharfedale is centre left, with the steeper left-bank tributary of Gill Beck coming from centre right. The village of Kettlewell lies at the confluence.

Photo: Ken Atkinson

Figure 1.2 Environmental and human controls on the Upper Wharfedale environmental system.

In terms of physiographic evolution, the most influential events were the many glacial episodes during the Pleistocene epoch of the Quaternary period (Atkinson, in Butlin 2003). During the most recent glaciation, namely the Devensian, glaciers entered Upper Wharfedale from local ice accumulation centres on plateau summits in the Pennine uplands such as Langstrothdale Chase, and flowed south-eastwards down Langstrothdale. On meeting Buckden Pike, the ice split into a stream flowing north-eastwards along Bishopdale and into Wensleydale and a stream flowing south-eastwards down Wharfedale. The Wharfedale ice was joined by Littondale ice, and the combined ice stream eroded the truncated spur of Kilnsey Crag in Great Scar Limestone (Plate 1.2). The power of glacial erosion is evidenced by the classic U-shaped valleys of Upper Wharfedale, Littondale and Bishopdale.

During periods of glacial retreat, moraines were deposited in valley bottoms and on lower valley side slopes. These are thought by some geographers to have initially dammed the river flow but to have been breached since. According to this hypothesis, the present flat alluvial floor of Upper Wharfedale held lakes in late glacial and early postglacial times. During deglaciation, when sub-surface drainage was prevented by permafrost, meltwaters eroded marginal channels along valley sides. At Conistone village the impressive ravine of Conistone Dib narrows to 1 m width in places, with fluvial potholes evident on the side walls. This dramatic gorge was sculptured by a glaciofluvial stream issuing from the front of or from beneath a retreating glacier (Plate 1.3).

Since the Pleistocene epoch, geomorphic activity in Upper Wharfedale has been of two main types. First, weathering and erosion of hill slopes have produced valley-side scars and small screes. Second, the channels of the river Wharfe and its tributaries have been carrying out fluvial action, with periods of incision (i.e. vertical erosion) alternating with periods of lateral channel migration and aggradation (i.e. deposition of sediments) to produce prominent alluvial terraces. River action in the early Holocene epoch was mainly a reworking of coarse cobbles and rocks from Pleistocene glacial materials, but more recent terraces are composed of finer-grained sediments produced by the erosion of hill slopes.

Figure 1.3 Geology of Upper Wharfedale, North Yorkshire.

After the final retreat of the ice sheets and valley glaciers, the dale was recolonized by natural vegetation and associated wildlife. Birch and pine trees arrived quite quickly, followed by larger broad-leaved trees in early postglacial times. Ecological and anthropogenic impacts have had a great influence on the environmental systems of Upper Wharfedale ever since. Here, as wherever there are human settlement and l...