Earth Environments: Past, Present and Future

Earth Environments

Cyclone Nargis just before it hits land in Mayanmar (Burma). Source: NASA

Earth Environments

Past, Present and Future

David Huddart and Tim Stott

Liverpool John Moores University, UK

A John Wiley & Sons, Ltd., Publication

This edition first published 2010

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Library of Congress Cataloguing-in-Publication Data

Huddart, David.

Earth environments : past, present, and future / David Huddart and Tim Stott.

p. cm.

ISBN 978-0-471-48532-2 (cloth)

1. Earth sciences–Textbooks. I. Stott, Tim. II. Title.

QE28.H84 2010

550–dc22

2009049245

ISBN: 978-0-471-4853-2 (HB) 978-0-471-48533-9 (PB)

A catalogue record for this book is available from the British Library.

Set in 10/12 pt Times by Laserwords Private Limited, Chennai, India

Printed in Malaysia by Vivar Printing Sdn Bhd

First printing 2010

Contents

Introduction xi

SECTION I Introduction to Earth Systems 1

1 Introduction to Earth Systems 3

1.1 Introduction to the Earth’s formation 4

1.2 Introduction to Earth spheres 5

1.3 Scales in space and time 6

1.4 Systems and feedback 7

1.5 Open and closed flow systems 8

1.6 Equilibrium in systems 9

1.7 Time cycles in systems 11

Exercises 13

References 13

SECTION II Atmospheric and Ocean

Systems 15

2 Structure and Composition of the

Atmosphere 17

2.1 Structure of the atmosphere 18

2.2 Composition of the atmosphere 18

Exercises 22

References 23

Further reading 23

3 Energy in the Atmosphere and the Earth

Heat Budget 25

3.1 Introduction 26

3.2 Solar radiation 26

Exercises 36

References 36

Further reading 36

4 Moisture in the Atmosphere 37

4.1 Introduction 38

4.2 The global hydrological cycle 38

4.3 Air stability and instability 42

4.4 Clouds 42

4.5 Precipitation 44

Exercises 48

References 48

Further reading 48

5 Atmospheric Motion 49

5.1 Introduction 50

5.2 Atmospheric pressure 50

5.3 Winds and pressure gradients 51

5.4 The global pattern of atmospheric

circulation 55

Exercises 58

References 59

Further reading 59

6 Weather Systems 61

6.1 Introduction 62

6.2 Macroscale synoptic systems 62

6.3 Meso-scale: Local winds 71

6.4 Microclimates 74

6.5 Weather observation and forecasting 79

Exercises 86

References 87

Further reading 87

7 World Climates 89

7.1 Introduction 90

vi CONTENTS

7.2 Classification of climate 90

Exercises 100

References 100

Further reading 100

8 Ocean Structure and Circulation Patterns 101

8.1 Introduction 102

8.2 Physical structure of the oceans 102

8.3 Temperature structure of the oceans 105

8.4 Ocean circulation 105

8.5 Sea-level change 109

Exercises 110

References 110

Further reading 110

9 Atmospheric Evolution and Climate Change 111

9.1 Evolution of the Earth’s atmosphere 112

Exercises 115

References 115

Further reading 115

10 Principles of Climate Change 117

10.1 Introduction 118

10.2 Evidence for climate change 118

10.3 Causes of climate change 125

Exercises 136

References 136

Further reading 136

SECTION III Endogenic Geological

Systems 137

11 Earth Materials: Mineralogy, Rocks and

the Rock Cycle 139

11.1 What is a mineral? 140

11.2 Rocks and the rock cycle 148

11.3 Vulcanicity and igneous rocks 151

11.4 Sedimentary rocks, fossils and

sedimentary structures 153

11.5 Metamorphic rocks 159

Exercises 162

References 163

Further reading 163

12 The Internal Structure of the Earth 165

12.1 Introduction 166

12.2 Evidence of the Earth’s composition

from drilling 166

12.3 Evidence of the Earth’s composition

from volcanoes 167

12.4 Evidence of the Earth’s composition

from meteorites 167

12.5 Using earthquake seismic waves as

Earth probes 168

Exercises 171

References 171

Further reading 171

13 Plate Tectonics and Volcanism: Processes,

Products and Landforms 173

13.1 Introduction 174

13.2 Global tectonics: how plates, basins

and mountains are created 174

13.3 Volcanic processes and the global

tectonic model 177

13.4 Magma eruption 186

13.5 Explosive volcanism 194

13.6 Petrographic features of volcaniclastic

sediments 200

13.7 Transport and deposition of

pyroclastic materials 200

13.8 The relationship between volcanic

processes and the Earth’s atmosphere

and climate 210

13.9 Relationships between volcanic

eruptions and biotic evolution 216

13.10 Plate tectonics, uniformitarianism and

Earth history 217

Exercises 223

References 223

Further reading 225

CONTENTS vii

14 Geotectonics: Processes, Structures and

Landforms 227

14.1 Introduction 228

14.2 Tectonic structures 228

14.3 Tectonic structures as lines of weakness

in landscape evolution 234

Exercises 235

References 235

Further reading 235

SECTION IV Exogenic Geological Systems 237

15 Weathering Processes and Products 239

15.1 Introduction 240

15.2 Physical or mechanical

weathering 242

15.3 Chemical weathering 251

15.4 Measuring weathering rates 262

15.5 Weathering landforms 262

Exercises 267

References 267

Further reading 268

16 Slope Processes and Morphology 269

16.1 Introduction 270

16.2 Slopes: mass movement 270

16.3 Hillslope hydrology and slope

processes 297

16.4 Slope morphology and its evolution 305

Exercises 318

References 318

Further reading 319

17 Fluvial Processes and Landform–

Sediment Assemblages 321

17.1 Introduction 322

17.2 Loose boundary hydraulics 322

17.3 The energy of a river and its ability to

do work 323

17.4 Transport of the sediment load 325

17.5 Types of sediment load 327

17.6 River hydrology 328

17.7 The drainage basin 329

17.8 Drainage patterns and their

interpretation 332

17.9 Fluvial channel geomorphology 332

Exercises 376

References 376

Further reading 378

18 Carbonate Sedimentary Environments and

Karst Processes and Landforms 379

18.1 Introduction 380

18.2 Carbonate sedimentary environments

and the creation of carbonate rock

characteristics 380

18.3 Evaporites 394

18.4 Carbonate facies models 395

18.5 Karst processes 401

Exercises 427

References 428

Further reading 429

19 Coastal Processes, Landforms and

Sediments 431

19.1 Introduction to the coastal zone 432

19.2 Sea waves, tides and tsunamis 433

19.3 Tides 439

19.4 Tsunamis 445

19.5 Coastal landsystems 445

19.6 Distribution of coastal landsystems 489

19.7 The impact of climatic change on

coastal landsystems: What lies in the

future? 492

Exercises 498

References 498

Further reading 499

20 Glacial Processes and Landsystems 501

20.1 Introduction 502

20.2 Mass balance and glacier formation 504

viii CONTENTS

20.3 Mass balance and glacier flow 510

20.4 Surging or galloping glaciers 512

20.5 Processes of glacial erosion and

deposition 515

20.6 Glacial landsystems 536

Exercises 562

References 562

Further reading 563

21 Periglacial Processes and Landform–

Sediment Assemblages 565

21.1 Introduction to the term ‘periglacial’ 566

21.2 Permafrost 566

21.3 Periglacial processes and landforms 569

21.4 Frost heaving and frost thrusting 571

21.5 Landforms associated with frost

sorting 573

21.6 Needle ice development 574

21.7 Frost cracking and the development of

ice wedges 574

21.8 Growth of ground ice and its decay,

and the development of pingos,

thufurs and palsas 578

21.9 Processes associated with snowbanks

(nivation processes) 583

21.10 Cryoplanation or altiplanation

processes and their resultant

landforms 585

21.11 The development of tors 588

21.12 Slope processes associated with the

short summer melt season 593

21.13 Cambering and associated structures 596

21.14 Wind action in a periglacial climate 597

21.15 Fluvial processes in a periglacial

environment 600

21.16 Alluvial fans in a periglacial region 602

21.17 An overview of the importance of

periglacial processes in shaping the

landscape of upland Britain 603

21.18 The periglaciation of lowland Britain 607

Exercises 607

References 607

22 Aeolian (Wind) Processes and

Landform–Sediment Assemblages 611

22.1 Introduction 612

22.2 Current controls on wind systems 613

22.3 Sediment entrainment and processes of

sand movement 613

22.4 Processes of wind transport 614

22.5 Aeolian bedforms 616

22.6 Dune and aeolian sediments 629

22.7 Dust and loess deposition 631

22.8 Wind erosion landforms 633

Exercises 637

References 637

Further reading 639

SECTION V Principles of Ecology and

Biogeography 641

23 Principles of Ecology and Biogeography 643

23.1 Introduction 644

23.2 Why do organisms live where they do? 644

23.3 Components of ecosystems 647

23.4 Energy flow in ecosystems 651

23.5 Food chains and webs 657

23.6 Pathways of mineral matter

(biogeochemical cycling) 660

23.7 Vegetation succession and climaxes 665

23.8 Concluding remarks 681

Exercises 682

References 683

Further reading 683

24 Soil-forming Processes and Products 685

24.1 Introduction 686

24.2 Controls on soil formation 686

24.3 Soils as systems 689

24.4 Soil profile development 690

24.5 Soil properties 696

24.6 Soil description in the field 704

24.7 Key soil types, with a description and

typical profile 707

24.8 Podsolization: theories 711

CONTENTS ix

24.9 Soil classification 712

24.10 Regional and local soil distribution 720

24.11 The development of dune soils: an

example from the Sefton coast 729

24.12 The development of woodland soils in

Delamere Forest 730

24.13 Intrazonal soils caused by topographic

change 731

24.14 Palaeosols 731

Exercises 732

References 732

Further reading 733

25 World Ecosystems 735

25.1 Introduction 736

25.2 The tundra ecozone 737

25.3 The tropical (equatorial) rain forest, or

humid tropics sensu stricto, ecozone 744

25.4 The seasonal tropics or savanna

ecozone 750

25.5 Potential effects of global warming on

the world’s ecozones 757

Exercises 759

References 759

Further reading 759

SECTION VI Global Environmental Change:

Past, Present and Future 761

26 The Earth as a Planet: Geological Evolution

and Change 763

26.1 Introduction 764

26.2 How unique is the Earth as a planet? 764

26.3 What do we really know about the early

Earth? 765

26.4 The early geological record 765

26.5 The first Earth system 768

26.6 How did the Earth’s core form? 768

26.7 Evolution of the Earth’s mantle 769

26.8 Evolution of the continental crust 777

Exercises 778

References 779

Further reading 779

27 Atmospheric Evolution and Climate Change 781

27.1 Evolution of the Earth’s atmosphere 782

27.2 Future climate change 783

Exercises 788

References 788

Further reading 788

28 Change in Ocean Circulation and the

Hydrosphere 789

28.1 Introduction 790

28.2 Sea-level change and the

supercontinental cycle 790

28.3 Ocean circulation in a warming climate 794

Exercises 795

References 795

Further reading 795

29 Biosphere Evolution and Change in the

Biosphere 797

29.1 Introduction 798

29.2 Mechanisms of evolution in the fossil

record 798

29.3 The origins of life 801

29.4 An outline history of the Earth’s

biospheric evolution 803

29.5 Mass extinctions and catastrophes in

the history of life on Earth 817

Exercises 824

References 825

Further reading 825

30 Environmental Change: Greenhouse and

Icehouse Earth Phases and Climates Prior

to Recent Changes 827

30.1 Introduction 828

30.2 Early glaciations in the Proterozoic

phase of the Pre-Cambrian (the

Snowball Earth hypothesis) 828

30.3 Examples of changes from greenhouse

to icehouse climates in the Earth’s past 833

x CONTENTS

30.4 Late Cenozoic ice ages: rapid climate

change in the Quaternary 845

30.5 Late Glacial climates and evidence for

rapid change 852

30.6 The Medieval Warm Period or Medieval

Climate Optimum and the Little Ice

Age 860

Exercises 864

References 864

Further reading 866

31 Global Environmental Change in the Future 867

31.1 Introduction 868

31.2 Future climate change 868

31.3 Change in the geosphere 869

31.4 Change in the oceans and hydrosphere 872

31.5 Change in the biosphere 873

31.6 A timeline for future Earth 873

31.7 Causes for future optimism? 874

31.8 Concluding remarks 876

Exercises 877

References 877

Further reading 878

Index 879

Introduction

In the year that the major part of this book has been written there

has never been a greater need for an understanding of modern

Earth processes, how these have changed over geological time

and how they may impact on the planet’s future. As we write this

preface in early May 2008 a natural disaster has just occurred in

the Irrawaddy delta in Mayanmar (the former Burma), when a

tropical cyclone in the Bay of Bengal (see Frontispiece) produced

a storm surge in the delta area, resulting in catastrophic loss of life,

initially from extremely strong winds and flooding (Figure 0.1).

Media reports on such natural disasters, whether floods, tsunamis,

earthquakes, volcanoes or mass movements, rightly stress the

human impact, but there is much to understand too about the

physical processes behind them.

We might ask ourselves whether global warming made Cyclone

Nargis worse, as some scientists have argued that storms are more

likely in a warming world. Similar debates followed Hurricane

Katrina in the Gulf of Mexico in 2005. Warmer seas could make

such storms more intense, though not more frequent. In 2007

reports from the Intergovernmental Panel on Climate Change

suggested that it was likely that future cyclones would be more

intense, while other research has suggested that future storm

strength might increase in some places but decrease in others.

The fact that global warming is now having acknowledged

repercussions, which are reported in the press and on television

on a regular basis, has to have a central place in a book on Earth

environments. Currently there is a preoccupation with climate

change brought about by the activities of mankind since the

Industrial Revolution, and rightly so, because global warming is

playing a crucial role in present-day global processes, whether in

the atmosphere, the oceans, geomorphological processes or the

ecology. There are effects throughout all the Earth’s systems and

many feedback loops are occurring because of the warming. We

are rightly concerned with what might happen to the Earth in

the future as a result of these climatic changes, but it has to be

realized that the planet has had many climatic oscillations, both

warmer and cooler, on a bigger scale than that seen today, though

these occurred prior to human evolution. The difference now is

that humans are the dominant controller of certain atmospheric

processes that are contributing in a major way to climatic change.

We hope that we can learn from similar climate changes in the

geological record in order to show that we need to alter our

current wilful disregard for our environment.

The ‘anthropocene’, as the current period of man-induced

change has been called, is hopefully not the next phase of global

mass extinction, where the causes of that extinction are man￾imposed. Whilst global mass extinctions have similarly been

common in the history of life on Earth, they have never before

been directly caused by us. Currently, however, this is what is

happening, and the World Wildlife Fund Living Planet Index

illustrates this very well. It monitors the 302 species of mammal,

811 birds, 83 amphibians and 40 reptiles on the planet and has

Figure 0.1 Before and after satellite images – taken on 15 April

2008 (top) and 5 May 2008 (bottom) – showing the extent of

flooding along the Mayanmar (Burma) coast as a result of Cyclone

Nargis. (Source: NASA/MODIS Rapid Response Team)

xii INTRODUCTION

found from figures published this yearthat populations decreased

by an average of 27% between 1970 and 2005. Land-based

species fell by 25% over this period, whilst marine species were

particularly hard-hit,falling by 28%. Seabirds have suffered a rapid

decline of around 30% since the mid 1990s. Most of the problem

is due to development, overfishing, intensive farming, habitat

loss, wildlife trade, pollution and man-made climate change. The

latter will be an increasingly important factor affecting species

in the next 30 years. Overall we are consuming some 25% more

natural resources than the Earth can replace.

In the past, mass extinctions have usually been caused by

the repercussions of impact from extraterrestrial bodies such

as comets; by major volcanic processes, the build-up of huge

plateau basalt provinces and supervolcanoes; by major phases of

glaciation; and by the effects all of these have had on the Earth’s

atmospheric processes. In fact, it appears that human populations

may have been decimated by the Toba supervolcano 70 000 years

ago and that the current human domination of the planet started

after the repercussions of that event from a very small population

base, estimated to have been as low as 2000 people.

Another environmental natural disaster has just occurred

literally in the middle of the writing of this preface: a large

earthquake, 7.9 on the Richter scale, in Wenchuan County in

the Sichuan Province of China, 92 km north-west of Chengdu,

on 12 May 2008 (Figure 0.2). The death toll stands already

at over 50 000 people after only a few days. A further strong

USGS ShakeMap: EASTERN SICHUAN, CHINA

Mon May 12, 2008 06:28:01 GMT M 7.9 N31.02 E103.37 Depth: 19.0 km ID:2008ryan

35°

30°

100° 105° 110°

Map Version 7 Processed Tue May 13, 2005 09:12:25 AM MDT−NDT REVIEWED BY HUMAN

IV

1.4-3.9

1.1-3.4

none

Light

V

3.9-9.2

3.4-8.1

Very light

Moderate

X+

>124

>116

Very

Heavy

Extreme

IX

65-124

60-116

Heavy

Violent

VIII

34-65

31-60

Moderate

Heavy

Severe

VII

18-34

16-31

Moderate

Very Strong

VI

9.2-18

8.1-16

Light

Strong

II-III

.17-1.4

0.1-1.1

none

Weak

I

<.17

<0.1

none

Not felt PERCEIVED

SHAKING

POTENTIAL

DAMAGE

PEAK ACC(%g)

PEAK VEL(cm/s)

INSTRUMENTAL

INTENSITY

Figure 0.2 Earthquake shake map. (Source: Wikimedia Commons. USGS provided data on 12 May 2008, http://www.earthquake.usgs.gov/

eqcenter/shakeup/global/shake/2008ryan)

INTRODUCTION xiii

aftershock at 5.9 occurred on 16 May and there have been many

others since, with associated landslides, mudflows and threats of

floods. This emphasises that it is not just atmospheric processes

that humans have to worry about, but uncontrollable natural

tectonic and volcanic processes on a variety of scales, inflicting

damage wherever humans happen to live close by. We can do

little to prevent such disasters, except perhaps to use increasingly

sophisticated technology to, for example, build earthquake-proof

buildings. Unfortunately such building do not appear to have

existed in China, where many schools and poorly-constructed

flats failed (Figure 0.3). It may be possible to accelerate small￾scale movement along known fault lines, rather than to let the

pressure build up (so that when the energy is liberated it is on a

devastating scale), or to divert lava flows away from settlements.

The search for predictors of natural disasters is another way of

moving people quickly away from the likely impact zones.

However, when it comes to the megascale tsunami, super￾volcanic eruption or superearthquake, humans can do nothing

much in the face of such potentially devastating natural disas￾ters. Some of these megascale events have not been witnessed by

human populations in historical time but they have occurred in

the geological past and will do so again as part of the Earth’s set

of processes, which operate both internally within the Earth and

externally from the solar system.

For these reasons we feel that there is a needfor more education

about the past, current and future processes that occur on and

in our planet. This is especially so when the United Nations

Educational, Scientific and Cultural Organization (UNESCO)

and the International Union of Geological Sciences have jointly

declared 2008 as the International Year of Planet Earth (IYPE),

which actually lasts from late 2007 to early 2009. The aim of

this year is to raise ‘worldwide public and political awareness

Figure 0.3 Building collapse and destruction: here a single door

frame bearing a portrait of Chairman Mao remained standing in a

pile of debris, on the road heading to Wenyuan, the epicentre.

(Source: Wikimedia Commons, http://zh.wikipedia.org/wiki/

User:Miniwiki)

of the vast (but often under-used) potential of Earth sciences

for improving the quality of life and safeguarding the planet.’

It is hoped that the public’s imagination can be captured so

that information related to the Earth can be used to ensure

that it is a safer, healthier and wealthier place for our future

children. The science programme consists of 10 broad, socially

relevant and multidisciplinary themes: health, climate, ground

water, ocean, soils, deep Earth, megacities, resources, hazards and

life. Further information related to each theme can be obtained

at http://www.yearofplanetearth.org.

2007–2009 is also the 4th International Polar Year, established

by the International Council for Science and the World Meteo￾rological Organization, where the biggest challenge for scientists

is to understand the relationships between changing climatic

conditions and the dynamics of polar ice.

We consider that there is also the need for everyone on the

planet to become more knowledgeable about the processes that

currently operate on and in the Earth. Humans need to be

educated about the fascinating, yet potentially lethal, set of atmo￾spheric, surface and internal processes that interact to produce

our living environment. Without education, decisions cannot be

made sensibly by individuals, by politicians, or by profession￾als with direct involvement with environmental organizations

of various kinds. Everyone can benefit from better education

about the planet on which we live. We hope that reading this

book will foster in the reader not just a greater awareness but a

greater enthusiasm for Earth processes. However, our main aim

is to provide a textbook for introductory university courses in

Earth Systems Science, Environmental Sciences, Ecology, Geol￾ogy, Earth Sciences and Physical Geography, and thus this book

has been designed for use in a wide range of courses which discuss

environmental and Earth processes, both those that currently

operate and those that have operated in the geological past.

In order to foster a greater understanding of Earth systems

science we need to build an understanding of the whole Earth

system, and to do that we have to increase our knowledge of the

component parts and the ways in which these interact. So we need

to know how the Earth works as a planet today and how some

components of the systems have evolved over geological time in

response to changes in others. We must try to be in a position to

predict future changes and how the Earth’s processes will operate

following them.

At the heart of environmental sciences today, in the past and

in the future is the climate system. Government organizations are

trying to develop risk-based predictions of the future state of the

climate on all kinds of scales, both spatially and in terms of time.

These predictions are extremely important as they form the basis

on which society can build adaptation and mitigation strategies,

although there is little in this book that covers these strategies and

the accuracy of such predictions is difficult to establish. However,

we do try to predict wherever possible the likely future impacts

of climate change on whichever part of the Earth system we are

studying. One of the major effects already noticeable is on the

biodiversity of the planet, the huge variety of plants and animals

which forms a key aspect of global ecosystems. It is apparent