Environmental Geology

Environmental Geology 9EDITION

TH

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Environmental Geology

EDWARD A. KELLERUniversi ty of California, Santa Barbara

99EDITIONTH

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Acquisitions Editor: Andrew DunawayEditor in Chief, Geosciences and Chemistry: Nicole FolchettiMarketing Manager: Maureen McLaughlinProject Editor: Crissy DudonisEditorial Assistant: Kristen SanchezMarketing Assistant: Nicola HoustonManaging Editor, Geosciences and Chemistry: Gina M. CheselkaProject Manager: Edward ThomasFull Service/Composition: GGS Higher Education Resources, PMGProduction Editor, Full Service: Karpagam JagadeesanArt Director: Mark OngCover and Interior Design: Jill Little

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Cover and Title Page Photo: Muddy runoff from heavy rain causing erosion in Madeira Islands. (Photo by Medford Taylor/National Geographic).

2011, 2000, 1996 by Pearson Education, Inc.Earlier editions 1992 by Macmillan Publishing Company; 1988, 1985, 1982, 1979, 1976 by Merrill Publishing Company.

Pearson Prentice HallPearson Education, Inc.Upper Saddle River, New Jersey 07458

All rights reserved. No part of this book may be reproduced, in any form or by any means, without permissionin writing from the publisher.

Pearson Prentice Hall is a trademark of Pearson Education, Inc.

Library of Congress Cataloging-in-Publication Data

Keller, Edward A.Environmental geology / Edward A. Keller. 9th ed.

p. cm.Includes bibliographical references and index.ISBN-13: 978-0-321-64375-9 (alk. paper)ISBN-10: 0-321-64375-5 (alk. paper)1. Environmental geology Textbooks. I. Title.

QE38.K45 2011

550 dc22 2009045752

Printed in the United States of America10 9 8 7 6 5 4 3 2 1

ISBN-10: 0-32-164375-5 / ISBN-13: 978-0-32-164375-9 [Student]ISBN-10: 0-32-171437-7 / ISBN-13: 978-0-32-171437-4 [Books la Carte]

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PART 1 FOUNDATIONS

OF ENVIRONMENTAL

GEOLOGY

CHAPTER 1 Philosophy and Fundamental Concepts 2

CHAPTER 2 Earth Materials and Processes 28

CHAPTER 3 Soils and Environment 64

CHAPTER 4 Ecology and Geology 92

PART 2 HAZARDOUS EARTH

PROCESSES

CHAPTER 5 Introduction to NaturalHazards 116

CHAPTER 6 Rivers and Flooding 136

CHAPTER 7 Slope Processes, Landslides,and Subsidence 173

CHAPTER 8 Earthquakes and RelatedPhenomena 206

CHAPTER 9 Volcanic Activity 259

CHAPTER 10 Coastal Hazards: CoastalErosion and Hurricanes 290

CHAPTER 11 Impact of ExtraterrestrialObjects 322

PART 3 RESOURCES

AND POLLUTION

CHAPTER 12 Water Resources 344

CHAPTER 13 Water Pollution and Treatment 372

CHAPTER 14 Mineral Resources and Environment 403

CHAPTER 15 Energy Resources 430

PART 4 GLOBAL PERSPECTIVES

AND SOCIETY

CHAPTER 16 Global Climate Change 474

CHAPTER 17 Geology, Society,and the Future 505

Brief Contents

v

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To all my undergraduate and graduate students who have

been a source of inspiration to my research and writing for

over 30 years. Especially Tom Rockwell, Joan Florsheim,

Nick Pinter, Anne Mac Donald, Taz Tally, Dave Best, Molly

Trecker, Lee Harrison, Larry Gurrola, and Duane DeVecchio

Dedication

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Preface xvii

PART 1 FOUNDATIONS OF

ENVIRONMENTAL GEOLOGY

CHAPTER 1

Philosophy and Fundamental Concepts 2

* Case History Easter Island: Are We on the Same Path at a Global Scale? 3

Introduction to Environmental Geology 4

* A Closer Look Earth s Place in Space 4

Fundamental Concepts of Environmental Geology 8

Concept One: Human Population Growth 9

Exponential Growth 9

Human Population through History 10

* Putting Some Numbers On Exponential Growth 11

Population Growth and the Future 12

Concept Two: Sustainability 13

Concept Three: Earth as a System 14

Input-Output Analysis 14

Concept Four: Hazardous Earth Processes 17

Natural Hazards That Produce Disasters Are BecomingSuperdisasters Called Catastrophes 17

* A Closer Look The Gaia Hypothesis 18

Concept Five: Scientific Knowledge and Values 19

Culture and Environmental Awareness 23

Why Is Solving Environmental Problems So Difficult? 24

Precautionary Principle 24

Science and Values 25

CHAPTER 2

Earth Materials andProcesses 28

The Geologic Cycle 29

The Tectonic Cycle 29

* A Closer Look The Wonder of Mountains 33

The Rock Cycle 38

The Rock Cycle and the Tectonic Cycle 38

The Hydrologic Cycle 39

Biogeochemical Cycles 39

Rocks 41

* A Closer Look Minerals 42

The Strength of Rocks 43

* Putting Some Numbers On Stress, Strain, and Strength of Rocks 44

Types of Rocks 47

Three Rock Laws 51

Rock Structures 52

* Case History St. Francis Dam 54

Surficial Processes: Ice and Wind 55

Ice 56

Wind 59

CHAPTER 3

Soils and Environment 64

Introduction to Soils 64

Soil Profiles 65

Soil Horizons 65

Soil Color 66

Soil Texture 67

Soil Structure 67

Relative Profile Development 67

Soil Chronosequences 68

Soil Fertility 68

Water in Soil 69

Soil Classification 69

Soil Taxonomy 70

Engineering Classification of Soils 70

Engineering Properties of Soils 70

* Putting Some Numbers On Properities of Soil 72

Rates of Soil Erosion 76

Agriculture and Soil Conservation 78

Sediment Pollution 80

* A Closer Look Universal Soil Loss Equation 80

* Case History Reduction of Sediment

Pollution, Maryland 81

Land Use and Environmental Problems of Soils 82

Urbanization 82

Off-Road Vehicles 82

ix

Contents

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Soil Pollution 85

Desertification 86

Soil Surveys and Land-Use Planning 87

CHAPTER 4

Ecology and Geology 92

Ecology for Geologists: BasicTerms 93

What Is an Ecosystem and How Does It Work? 94

Natural Service Functions of Ecosystems 95

Geology and Biodiversity 95

Biodiversity of Trees in North America and Europe 95

Community Effects and Keystone Species: How Are These Concepts Related to Geology? 96

Stream Processes and Ecology: The Story of MountainStreams, Elk, and Wolves in Yellowstone NationalPark 96

Coastal Geology, Kelp, Urchins, and Sea Otters 98

* Putting Some Numbers On The Population ofWolves 102

Factors That Increase or Decrease Biodiversity 103

What Factors Increase Biodiversity? 103

What Factors Reduce Biological Diversity? 104

Human Domination of Ecosystems 104

The Golden Rule of the Environment: A Geologic Perspective All About Timing 104

What Can We Do to Reduce the Human Footprint on the Environment? 105

* A Closer Look Seawalls and Biodiversity 105

Ecological Restoration 107

* A Closer Look Restoration of the Kissimmee River 107

* A Closer Look Restoration of the Florida Everglades 110

* A Closer Look Costal Sand Dune Restoration at Pocket Beaches: University

of California, Santa Barbara 111

PART 2 HAZARDOUS EARTH

PROCESSES

CHAPTER 5

Introduction to NaturalHazards 116

Hazards, Disasters, and Natural Processes 116

Natural Disasters: Loss of Life and Property Damages 116

x Contents

Why Natural Processes Are Sometimes Hazards 117

Magnitude and Frequency 117

The Benefits of Natural Hazards 117

* A Closer Look The Magnitude-Frequency Concept 119

Death and Damage Caused by Natural Hazards 120

Evaluating Hazards: History, Linkages, Disaster Prediction, and Risk Assessment 122

Fundamental Principles Concerning Natural Hazards 122

Role of History in Understanding Hazards 122

Linkages between Hazardous Events 123

Disaster Forecast, Prediction, and Warning 124

* A Closer Look Scientists, Hazards, and the Media 126

Risk Assessment 126

The Human Response to Hazards 127

Reactive Response: Impact of and Recovery fromDisasters 127

Anticipatory Response: Perceiving, Avoiding, and Adjustingto Hazards 128

Artificial Control of Natural Processes 129

Global Climate and Hazards 130

Population Increase, Land Use Change, and Natural Hazards 130

Population Increase and Hazardous Events 130

Land-Use Change and Hazardous Events 130

* A Closer Look Nevado del Ruiz: A Story of People, Land Use, and Volcanic Eruption 132

CHAPTER 6

Rivers and Flooding 136

Rivers: Historical Use 137

Streams and Rivers 137

Sediment in Rivers 139

River Velocity, Discharge, Erosion, and Sediment Deposition 139

Effects of Land-Use Changes 141

* A Closer Look History of a River 142

Channel Patterns and Floodplain Formation 144

River Flooding 146

* A Closer Look Magnitude and Frequency of Floods 146

Flash Floods and Downstream Floods 148

Urbanization and Flooding 150

The Nature and Extent of Flood Hazards 153

Factors That Cause Flood Damage 153

Effects of Flooding 153

* Case History Flash Floods in Eastern Ohio 153

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Adjustments to Flood Hazards 154

The Structural Approach 155

* A Closer Look Mississippi River Flooding 156

Channel Restoration: Alternative to Channelization 159

Flood Insurance 159

Flood-Proofing 159

Floodplain Regulation 160

Flood-Hazard Mapping 163

* Putting Some Numbers On Flood-HazardAnalysis 163

Relocating People from Floodplains: Examples from NorthCarolina and North Dakota 168

Personal Adjustment: What to Do and What Not to Do 168

Perception of Flooding 168

CHAPTER 7

Slope Processes, Landslides,and Subsidence 173

Introduction to Landslides 173

Slope Processes and Types of Landslides 174

Slope Processes 174

Types of Landslides 175

Slope Stability 176

Forces on Slopes 176

The Role of Earth Material Type 178

* Putting Some Numbers On Landslides 179

The Role of Slope and Topography 181

The Role of Climate 182

* A Closer Look Translation Slides along Bedding Planes 184

Contents xi

Subsidence 198

Withdrawal of Fluids 199

Sinkholes 199

Salt Deposits 200

Coal Mining 202

Perception of the Landslide Hazard 203

What You Can Do to Minimize Your Landslide Hazard 203

CHAPTER 8

Earthquakes and RelatedPhenomena 206

Introduction to Earthquakes 206

Earthquake Magnitude 206

Earthquake Catastrophes 209

Earthquake Intensity 209

Plate Boundary Earthquakes 211

Intraplate Earthquakes 212

Earthquake Processes 212

Faulting 212

Fault Types 214

Fault Zones and Fault Segments 216

Active Faults 216

* Case History Northridge, 1994 218

Tectonic Creep 220

Slow Earthquakes 220

Earthquake Shaking 220

Types of Seismic Waves 220

Seismograph 221

Frequency of Seismic Waves 222

Material Amplification 224

Directivity 226

Ground Acceleration during Earthquakes 226

Supershear 228

Depth of Focus 228

Earthquake Cycle 229

Stages of the Earthquake Cycle 229

The Dilatancy-diffusion Model 230

Earthquakes Caused by Human Activity 231

Reservoir-induced Seismicity 231

Deep Waste Disposal 232

Nuclear Explosions 232

Effects of Earthquakes 232

Shaking and Ground Rupture 233

Liquefaction 233

Landslides 233

Fires 234

The Role of Water 185

The Role of Time 185

Human Use and Landslides 186

Timber Harvesting 186

Urbanization 187

* Case History Vaiont Dam 187

Minimizing the Landslide Hazards 190

Identifying Potential Landslides 190

Preventing Landslides 192

* Case History: La Conchita Landslides 193

Warning of Impending Landslides 197

Correcting Landslides 197

Snow Avalanches 198

The Role of Vegetation 184

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Disease 235

Regional Changes in Land Elevation 235

Tsunami 235

* A Closer Look Indonesian Tsunami 236

How Do Earthquakes Cause a Tsunami? 240

Earthquake Risk and Earthquake Prediction 241

Estimation of Seismic Risk 242

Short-Term Prediction 244

Preseismic Deformation of the Ground Surface 244

Emission of Radon Gas 244

Seismic Gaps 244

Anomalous Animal Behavior (?) 245

Toward Earthquake Prediction 245

Sequence of Earthquakes in Turkey: Can One Earthquake Set Up Another? 245

* A Closer Look Twelve Centuries of Earthquakes on theSan Andreas Fault in Southern California 246

The Response to Earthquake Hazards 247

Earthquake Hazard-Reduction Programs 247

Adjustments to Earthquake Activity 248

* Putting Some Numbers On Earthquake Hazard Evaluation 248

* A Closer Look The Alaska Earthquake of 2002 and the value of Estimating Potential Ground Rupture 252

Earthquake Warning Systems 252

Perception of Earthquake Hazard 253

Personal and Community Adjustments: Before, During,and After an Earthquake 254

CHAPTER 9

Volcanic Activity 259

Introduction to Volcanic Hazards 259

Volcanism and Volcanoes 259

Volcano Types 260

Shield Volcanoes 262

Composite Volcanoes 263

Volcanic Domes 264

Cinder Cones 264

Volcano Origins 266

Volcanic Features 267

Craters, Calderas, and Vents 267

Hot Springs and Geysers 267

Caldera Eruptions 267

Volcanic Hazards 269

Lava Flows 269

Methods to Control Lava Flows 271

Pyroclastic Activity 272

Poisonous Gases 273

Debris Flows and Mudflows 276

xii Contents

Three Case Histories 277

Mt. Pinatubo 277

Mount St. Helens 277

Mt. Unzen, 1991 282

Forecasting Volcanic Activity 282

Seismic Activity 282

Thermal, Magnetic, and Hydrologic Monitoring 283

Topographic Monitoring 284

Monitoring Volcanic Gas Emissions 284

Geologic History 285

Volcanic Alert or Warning 285

Adjustment to and Perception of the Volcanic Hazard 286

CHAPTER 10

Coastal Hazards: Coastal Erosion and Hurricanes 290

Introduction to Coastal Hazards 290

Coastal Processes 291

Waves 291

* Putting Some Numbers On Waves 293

Beach Form and Beach Processes 295

Transport of Sand 295

Rip Currents 296

Coastal Erosion 297

Beach Budget 297

* Putting Some Numbers On A Beach Budget 298

Erosion Factors 299

Sea Cliff Erosion 299

Coastal Hazards and Engineering Structures 301

Hard Stabilization 301

Soft Stabilization 303

* A Closer Look Measuring Coastal Change 305

Human Activity and Coastal Erosion: Some Examples 306

The Atlantic Coast 306

The Gulf Coast 307

The Great Lakes 307

Tropical Cyclones 308

Hurricane Form and Process 308

* Case History Hurricane Katrina, Most Serious NaturalCatastrophe in U.S. History 309

Perception of and Adjustment to Coastal Hazards 315

Perception of Coastal Erosion 315

Adjustment to Coastal Hazards 316

* A Closer Look E-lines and E-zones 318

* Case History The Lighthouse Controversy 319

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CHAPTER 11

Impact of ExtraterrestrialObjects 322

Earth s Place in Space 322

Asteroids, Meteoroids, and Comets 322

Aerial Bursts and Impacts 323

* Case History The Tunguska Event 326

Impact Craters 327

Mass Extinctions 328

* A Closer Look Possible Extraterrestrial Impact 12,900 Years Ago 333

Late Cretaceous: K-T Boundary Mass Extinction 334

Minimizing the Impact Hazard 338

Risk Related to Impacts 338

Minimizing the Impact Hazard 339

* A Closer Look Near-Earth Objects 340

PART 3 RESOURCES AND

POLLUTION 343

CHAPTER 12

Water Resources 344

Water: A Brief Global Perspective 344

Surface Water 344

Surface Runoff and Sediment Yield 344

Factors Affecting Runoff and Sediment Yield 347

Groundwater 348

Aquifers 349

Groundwater Movement 351

Groundwater Supply 352

Interactions between Surface Water and Groundwater 352

Surface Water and Groundwater 352

* Putting Some Numbers On Groundwater Movement 354

* Case History Long Island, New York 356

* Case History The Edwards Aquifer, Texas Water Resource in Conflict 358

Desalination 360

Water Use 360

Movement of Water to People 360

Trends in Water Use 362

Water Conservation 363

Water Management in the Future 363

* A Closer Look Management of the Colorado River 363

Contents xiii

Globalization of Water Resources: The Concept of VirtualWater 367

Water and Ecosystems 367

* A Closer Look Wetlands 368

Removal of Dams 369

Emerging Global Water Shortages 370

CHAPTER 13

Water Pollution andTreatment 372

An Overview of Water Pollution 372

Selected Water Pollutants 373

Oxygen-Demanding Waste 373

Pathogenic Organisms 375

Nutrients 376

Oil 377

Toxic Substances 378

* Putting Some Numbers On Water Pollution 380

Sediment 383

Thermal Pollution 383

Surface-Water Pollution and Treatment 383

Point Sources of Surface-Water Pollution 383

Nonpoint Sources of Surface-Water Pollution 383

Reduction of Surface-Water Pollution: The CuyahogaRiver Success Story 384

* A Closer Look Acid Mine Drainage 385

Groundwater Pollution and Treatment 386

* Case History Cleaning up the Hudson 387

Comparison of Groundwater and Surface-WaterPollution 387

Exchanges between Groundwater and ItsSurroundings 388

* A Closer Look Selenium in the San Joaquin Valley 388

National Water-Quality Assessment Program 391

Saltwater Intrusion 391

Groundwater Treatment 393

Water-Quality Standards 395

Wastewater Treatment 396

Septic-Tank Sewage Disposal 396

Wastewater-Treatment Plants 397

Wetlands as Wastewater-Treatment Sites 398

Wastewater Renovation 398

* A Closer Look Boston Harbor Cleaning up a National Treasure 399

Federal Legislation 400

What Can Be Done to Reduce Effects of WaterPollution? 400

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CHAPTER 16

Global Climate Change 474

Global Change and Earth System Science:An Overview 474

Tools for Studying Global Change 475

The Geologic Record 475

Real-Time Monitoring 476

Mathematical Models 476

Earth s Atmosphere and Climate Change 476

The Atmosphere 477

Global Warming 478

The Greenhouse Effect 478

Global Temperature Change 481

Why Does Climate Change? 482

Solar Forcing 487

Volcanic Forcing 487

Anthropogenic Forcing 488

Potential Effects of Global Climate Change 490

Glaciers and Sea Ice 490

Climate Patterns 492

* A Closer Look Desertification 493

Sea Level Rise 495

Changes in the Biosphere 495

CHAPTER 14

Mineral Resources and Environment 403

Minerals and Human Use 403

Resources and Reserves 404

Availability and Use of Mineral Resources 404

Geology of Mineral Resources 407

Local Concentrations of Metals 407

Igneous Processes 408

* A Closer Look Plate Tectonics and Minerals 410

Metamorphic Processes 412

Sedimentary Processes 413

Biological Processes 415

Weathering Processes 416

Other Minerals from the Sea 417

Environmental Impact of Mineral Development 419

Impact of Mineral Exploration and Testing 419

Impact of Mineral Extraction and Processing 419

* A Closer Look Mining and Toxicity 422

* A Closer Look Homestake Mine, South Dakota 425

Recycling Mineral Resources 426

* A Closer Look Mine near Golden, Colorado, Is Transformed into a Golf Course 427

Minerals and Sustainability 427

CHAPTER 15

Energy Resources 430

Worry Over Energy Sources is Nothing New: Energy Shocks Past and Present 430

* A Closer Look Peak Oil: When Will It Occur and What Is Its Importance? 431

Energy Supply and Energy Demand 434

Fossil Fuels 435

* A Closer Look Energy Units 435

Coal 436

* A Closer Look Coal Sludge in the Appalachian Mountains 440

Hydrocarbons: Oil and Gas 440

Future of Oil 448

Fossil Fuel and Acid Rain 449

Environmental Effects of Acid Rain 450

A Solution to the Acid Rain Problem 451

Nuclear Energy 452

Energy from Fission 452

Geology and Distribution of Uranium 453

Reactor Design and Operation 453

xiv Contents

* A Closer Look Radioactivity 453

Risks Associated with Fission Reactors 455

The Future of Energy from Fission 456

Radioactive Waste Management 457

Energy from Fusion 459

Geothermal Energy 459

Geology of Geothermal Energy 459

Environmental Impact of Geothermal EnergyDevelopment 463

Future of Geothermal Energy 463

Renewable Energy Sources 463

Solar Energy 464

Hydrogen 465

Water Power 465

Wind Power 466

Biofuels 468

Conservation, Efficiency, and Cogeneration 469

Energy Policy for the Future 469

Sustainable Energy Policy 470

PART 4 GLOBAL PERSPECTIVES

AND SOCIETY 473

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* A Closer Look El Ni~no 496

Adaptation of Species to Global Warming 498

Strategies for Reducing the Impact of Global Warming 498

* A Closer Look Abrupt Climate Change 500

Coupling of Global Change Processes: Ozone Depletionand Global Warming 501

CHAPTER 17

Geology, Society, andthe Future 505

Introduction 505

Geology and Environmental Health 505

Some Geologic Factors of Environmental Health 506

Chronic Disease and the Geologic Environment 506

* A Closer Look Lead in the Environment 507

Heart Disease and the Geochemical Environment 507

Cancer and the Geochemical Environment 508

* A Closer Look Radon Gas 509

Air Pollution: Introduction and Geologic Perspective 512

Sources of Air Pollution 512

Air Pollutants 512

Air Toxins 512

Primary and Secondary Pollutants 513

Particulate Matter: PM 10 and PM 2.5 513

Urban Air Pollution 515

Contents xv

Indoor Air Pollution 517

Waste Management and Geology 518

Integrated Waste Management 518

Materials Management 518

Solid Waste Disposal 519

Hazardous Waste Management 523

* A Closer Look Love Canal 524

Environmental Analysis 528

Site Selection 528

Environmental Impact Analysis 528

Land Use and Planning 529

Environmental Law 531

Geology, the Environment, and the Future 534

Avoiding an Environmental Crisis: Focusing on What CanBe Done 534

Attaining Sustainability for the Future 534

Appendix A: Chemistry, Minerals, and Rocks 539

Appendix B: Rocks 553

Appendix C: Maps and Related Topics 555

Appendix D: How Geologists DetermineGeologic Time 563

Glossary 565

Index 587

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Environmental geology is the application of geologicinformation to the entire spectrum of interactionsbetween people and our physical environment. Those

students who become more interested in the subject may goon to become environmental geologists. They will takeadvanced courses in subjects such as engineering geology andhydrogeology.

Study of environmental geology is facilitated by previousexposure to an introductory physical geology or geographycourse. However, most students may not have the flexibility intheir undergraduate curriculum to take more than a singlegeology course. As a result, Environmental Geology is designedso that students who have had no previous exposure to thegeological sciences may comprehend and understand the prin-ciples of environmental geology. This requires that a fairamount of physical geology is presented along with discus-sion of relationships between geology and the environment.One important objective of the book is to present a broadspectrum of subject matter relevant to students studying awide variety of traditional sciences such as a chemistry,biology, geology, physical geography, and physics; liberal artsstudents studying subjects such as anthropology, economicsenvironmental studies, human geography, literature, politi-cal science, and sociology; and students who may be prepar-ing for professional schools such as engineering, architecture,or planning.

ORGANIZATION

The organization of the ninth edition is similar to the eighthwith new chapters on geology and ecosystems and impact ofextraterrestrial objects. Considerable discussion has beenadded concerning global warming.

The subject material for Environmental Geology is arrangedin four parts. Part 1 introduces fundamental principles im-portant in the study of environmental geology. The purposeis to set the philosophical framework for the remainder of thetext, as well as to introduce important aspects of geology nec-essary to undertake a study of applied geology. Emphasis ison geologic process and the study of the earth as a system.This is facilitated through study of earth materials such asminerals, rocks, soils as they relate to processes operating inthe solid earth, biosphere, hydrosphere (surface and ground-waters), and atmosphere.

Part 2 addresses the important subject of natural processes(hazards) that continue to make life on earth occasionally dif-ficult for people. These include flooding, landslides, earth-quakes, volcanoes, coastal erosion, and impact of extraterrestrial

objects. Discussion of hazardous natural processes is facilitat-ed through the introduction of numerous case histories thatrepresent the spectrum of hazards and the response of society.

Part 3 focuses on resources and pollution and includesdetailed discussions of water resources, water pollution, min-eral resources, and energy.

Part 4 is concerned with global climate change and link-ages between geology and society. For the ninth edition, thematerial on earth system science and global change as itrelates to global environmental problems has been revised toinclude a more thorough discussion of global warming. Thesubjects of environmental health, environmental impactanalysis, land-use planning, waste disposal and environmen-tal law have been combined into a single chapter that inte-grates these subjects and highlights the usefulness ofenvironmental geology to society.

SOME SPECIAL FEATURES

The ninth edition of Environmental Geology includes a com-plete reorganization of the chapters:

* The ninth edition presents some quantitative examplesin the Putting Some Numbers On boxes, which discuss avariety of processes, including: exponential growth;rock mechanics; soil mechanics; flood frequency analysis;landslide stability analysis; construction of a beach budget;groundwater movement; and earthquake hazard.

* Each chapter begins with a photograph and an accom-panying short explanatory narrative, followed by learn-ing objectives. The purpose of the learning objectivesis to inform students about what is important in thatchapter.

* Selected Case History boxes are separated from the generaltext so that students might better focus on importantissues.

* A Closer Look special feature boxes discuss important issuesor concepts separately from the general text.

* Key terms presented in the text are listed at the end ofeach chapter to further assist students in their study ofthe material.

* Critical thinking questions are provided for each chapterwith the intent of stimulating discussion of important is-sues related to environmental geology. There are only afew questions for each chapter but the emphasis is ondeveloping critical thinking skills about the text material.

Preface

xvii

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NEW TO THIS EDITION

* More quantitative exercises on rock mechanics, soil mec-hanics, average residence time, groundwater movement,and exponential growth.

* New chapter on links of geology to ecology.

* New coverage on glaciers, especially ice sheets.

* Complete revision of global climate change.

* Many revisions of Hazards chapter (especially earth-quakes, landslides, flooding, and coastal processes).

* New chapter on impact structures and global environ-ment, including mass extinctions.

SPECIAL NOTES TO STUDENTS

I wrote part of the first edition of Environmental Geologywhile I was still a graduate student at Purdue University. Asa student I was very interested in trying to understand thisnew field of environmental geology that a few people werebeginning to talk about. I taught a class in environmental ge-ology at Indiana University-Purdue University in Indi-anapolis, Indiana. At that time, in the early 1970s, we werejust becoming conscious of environmental problems andwere more concerned with identifying the problems ratherthan dealing with solutions. Since then, the field of envi-ronmental geology has grown substantially, and there aremany practicing professional environmental geologists. Thefocus has also shifted to finding solutions to environmentalproblems. This requires increased understanding of theapplication of geologic processes to the environment. As aresult, we need to know more about how the earth worksand how the subject of geology interrelates with other dis-ciplines, such as biology, chemistry, physics, and geography.Some of the most fruitful areas for research for future stu-dents will be interdisciplinary studies that combine one ormore of the other sciences. Environmental geology, how-ever, is more than just science. Our science may providepotential solutions to environmental problems and outlinethe risks of such processes as earthquakes and flooding.However, what we actually decide to do about our environ-mental problems is more related to our value systems. As aresult, subjects such as psychology, social anthropology, his-tory, human geography, political science, law and society,and economics come to the forefront. People who will solveenvironmental problems in the future will continue to bemore interdisciplinary in their research approach and theirstudy of the environment. The upshot of all this is that ourstudy of the environment is becoming broader on one handand more rigorous on the other. In response to this, I havemade no attempt to dodge difficult subjects such ashydraulic conductivity, fluid pressure in rocks and soils, andearthquake hazard evaluation. I am confident that students

xviii Preface

remain interested in obtaining the best possible educationand expect to be challenged. I have made every attempt todiscuss difficult subjects in a way that will enable studentsto better understand what is happening. However, many ofthese subjects are difficult, and considerable study is neces-sary to understand them thoroughly. Finally, more advancedcourses in areas such as hydrogeology, geochemistry, andseismology are suggested for those students who wish topursue these subjects further.

I have learned a great deal in preparing EnvironmentalGeology. I hope you enjoy reading the book and hope that someof you may pursue environmental geology as a career. A few ofyou may become so intensely interested that you will pursue aresearch and teaching career to better understand how ourearth works and how we might better solve environmentalproblems.

ACKNOWLEDGMENTS

Successful completion of a textbook that includes hundredsof photographs and illustrations as well as case historieswould not be possible without the cooperation of many in-dividuals, companies, and agencies. In particular, I greatlyappreciate the work of agencies such as the U.S. Geologi-cal Survey, which has an extensive environmental program,as well as individual state geological surveys, which haveprovided a great deal of information and concepts importantin the development of the subject of environmental geolo-gy. To all of those individuals who are so helpful in thisendeavor, I offer my sincere appreciation. Reviews ofchapters or the entire book in this or previous editions byPeter Adams, Roger J. Bain, Daniel Botkin, Douglas G.Brookings, William Chadwick, Carla D Antonio, LaurenceR. Davis, P. Thompson Davis, Thomas L. Davis, John G.Drost, Anne Erdmann, Edward B. Evenson, Richard V.Fisher, Stanley T. Fisher, Robert B. Furlong, H. G. Goodell,Cal Janes, Donald L. Johnson, Ernest K. Johnson, ErnestKastning, James Kennett, Bjrn Kjerfve, Harold L. Krivoy,Golbert LaFreniere, James R. Lauffer, Gene W. Lene, HugoLoaiciga, Mel Manalis, Robert Mathews, Richard Mauger,Marc McGinnes, Patricia Miller, Gary L. Millhollen, RobertM. Norris, June A. Oberdorfer, Roderic A. Parnell, AnneD. Pasch, John S. Pomeroy, James Dennis Rash, Charles J.Ritter, Derrick J. Rust, Paul T. Ryberg, William C.Sherwood, Robert Shuster, Frank Spera, Mark T. Steward,Samual E. Swanson, Taz Talley, Russel O. Utgard,and William S. Wise are acknowledged and are greatlyappreciated.

I am particularly indebted to the wonderful staff at Pren-tice Hall especially Crissy Dudonis, Sean Hale, MaureenMcLaughlin, Kristin Sanchez, Edward Thomas, KarpagamJagadeesan, and Clare Maxwell.

The Environmental Studies Program and the Departmentof Earth Science at the University of California, Santa Barbara,

A01_KELL3759_09_SE_FM.qxd 12/22/09 5:40 PM Page xviii

continue to provide a stimulating environment in which to doresearch and write. I would like to thank the many people whohave readily given their time in thoughtful discussion and helpin preparation of many aspects of Environmental Geology. In par-ticular, I would like to acknowledge the help of Tammy Schmit,Frankie Albarran and Bill Norrigton with word processing and

Preface xix

editing. This book would not be possible without the supportof my wife Valery who helps in many ways.

Edward A. KellerSanta Barbara, California

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Edward A. Keller is professor of environmental geology at the University

of California, Santa Barbara, where he holds a joint appointment with the

Environmental Studies Program and the Department of Earth Science.

Professor Keller s research focuses on natural hazards, including wildfire,

flooding, river processes, and earthquakes. He is also evaluating the

environmental impacts of ecotourism. Professor Keller received his doctorate

from Purdue University in 1973; as a graduate student, he wrote the first

five chapters of the first edition of Environmental Geology.

Professor Keller was elected a visiting Fellow of Emmanuel College of

Cambridge University, UK in 2000. He was the recipient of the Easter-

brook Distinguished Scientist award from the Geological Society of America

in 2004.

Professor Keller enjoys teaching and research, and hopes his textbooks

help students to appreciate geology and to assist them in becoming better

and more informed citizens in our complex world.

About the Author

xxi

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xxii

This book is carefully crafted to minimize environmental im-pact. The materials used to manufacture this book originatedfrom sources committed to responsible forestry practices. Thepaper is FSC certified. The printing, binding, and cover papercome from facilities that minimize waste, energy consump-tion, and the use of harmful chemicals.

Pearson closes the loop by recycling every out-of-datetext returned to our warehouse. We pulp the books, and the

pulp is used to produce items such as paper coffee cups andshopping bags. In addition, Pearson aims to become the firstclimate neutral educational publishing company.

The future holds great promise for reducing our impacton the Earth s environment, and Pearson is proud to be lead-ing the way. We strive to publish the best books with the mostup-to-date and accurate content, and to do so in ways thatminimize our impact on the Earth.

About our Sustainability Initiatives

A01_KELL3759_09_SE_FM.qxd 12/23/09 9:21 PM Page xxii

Environmental Geology 9EDITION

TH

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PART ONE

Foundations of Environmental Geology

CHAPTER 1

Philosophy and Fundamental Concepts

CHAPTER 2

Earth Materials and Processes

CHAPTER 3

Soils and Environment

CHAPTER 4

Ecology and Geology

1

People today may be more concerned with ourenvironment that ever before since the Industrial Revolu-tion. We have come to realize that, while we are generallybetter off now, rapid increase in world population and devel-opment of resources is straining our planet s natural supportsystem. We are concerned about global warming, energy sup-ply, water resources and pollution of our air, water, and land.We are struggling with how to provide a future for ourchildren and theirs that will include a high-quality envi-ronment with sufficient space for people as well as the incred-ible diversity of life with which we share our planet. In short,we are struggling to develop what we term sustainability.

Chapter 1 through 4 provided the philosophical frame-work and basic concepts for the remainder of the book. It ishoped that these chapters will whet your interest in learningmore about environmental geology. Chapter 1 discusses

what environmental geology is, how geologists work, thecultural basis of environmental awareness, environmentalethics, and the fundamental concepts important to the studyof environmental geology. Chapter 2 introduces the physicalenvironment through the geologic cycle. The term cycleemphasizes that most earth materials, such as air, water, min-erals, and rock, although changed physically and chemicallyand transported from place to place, are constantly beingreworked, conserved, and renewed by natural earthprocesses. Chapter 2 also introduces basic earth science ter-minology and the engineering properties of earth materials,excluding soil. Chapter 3 discusses soil in terms of its devel-opment, classification, engineering properties, and other fac-tors important to land-use planning. Chapter 4 is concernedwith links between geology and ecosystems. Links that aremanifested in fascinating and sometimes surprising ways.

The Colorado River, passing through Toroweap point of the Grand Canyon, exposes a variety of sedimentary rocks. Steep cliffs (right) are strong,resistant rock compared to the less resistant rock (at center) close to the river. (Getty Images/Panoramic Images)

M01_KELL3759_09_SE_C01.qxd 12/19/09 6:50 AM Page 1

12

Easter Island: A story of the rise and fall of a society that overused its resources. (Tom Till /Getty Images)

CHAPTER ONE

Philosophy and Fundamental Concepts

In this chapter, we discuss and definegeology and environmental geology,focusing on aspects of culture and soci-ety that are particularly significant toenvironmental awareness. We presentsome basic concepts of environmentalscience that provide the philosophicalframework of this book. After readingthis chapter, you should be prepared todiscuss the following:

* Geology and environmentalgeology as a science

* Increasing human population asthe number one environmentalproblem

* The concept of sustainability andimportant factors related to theenvironmental crisis

* Earth as a system and changes insystems

* The concepts of environmentalunity and uniformitarianism andwhy they are important to envi-ronmental geology

* Hazardous Earth processes

* Scientific knowledge and values

* The scientific method

* Geologic time and its significance

* The precautionary principle

* Why solving environmental prob-lems can be difficult

LEARNING OBJECTIVES


Chapter 1 Philosophy and Fundamental Concepts 3

Easter Island, at 140 km2, is a small, triangular-shaped, vol-canic island located several thousand kilometers west ofSouth America, with a subtropical climate. Polynesian peo-ple first reached the island approximately 1500 years ago.When the Polynesians first arrived, they were greeted by agreen island covered with forest, including large palm trees.By the sixteenth century, 15,000 to 30,000 people were liv-ing there. They had established a complex society spreadamong small villages, and they raised crops and chickens tosupplement the fish, marine mammals, and seabirds thatsustained their diet. For religious reasons, they carved mas-sive statues (called moai) from volcanic rock. The statueshave the form of a human torso with stone headdresses.Most are about 7 m high (21 ft), but some are higher than20 m. The statues were moved into place at various loca-tions on the island using ropes and tree trunks as rollers.

When Europeans reached Easter Island in the seven-teenth century, only about 2000 people were living on theisland. The main symbols of the once-vibrant civilizationwere the statues, most of which had been toppled anddamaged. No trees were growing on the island, and thepeople were living in a degraded environment.

Why Did the Society Collapse?

Evidently, the society collapsed in just a few decades, prob-ably as a result of degradation of the island s limitedresource base. As the human population of the islandincreased, more and more land was cleared for agriculture,while remaining trees were used for fuel and for moving thestatues into place. Previously, the soils were protectedbeneath the forest cover and held water in the subtropicalenvironment. Soil nutrients were probably supplied by dustfrom thousands of kilometers away that reached the islandon the winds. Once the forest was cleared, the soils erodedand the agricultural base of the society was diminished. Lossof the forest also resulted in loss of forest products necessaryfor building homes and boats, and, as a result, the peoplewere forced to live in caves. Without boats, they could nolonger rely on fish as a source of protein. As populationpressure increased, wars between villages became com-mon, as did slavery and even cannibalism, in attempts tosurvive in an environment depleted of its resource base.

Lessons Learned

The story of Easter Island is a dark one that vividly pointsto what can happen when an isolated area is deprived ofits resources through human activity: Limited resources can-not support an ever-growing human population.

Although the people of Easter Island did deplete theirresources, the collapse of their society had some factorsthey could not understand or recognize. Easter Island hasa naturally fragile environment1 compared to many otherislands the Polynesians colonized.

* The island is small and very isolated. The inhabitantscouldn t expect help in hard times from neighboringislands.

* Volcanic soils were originally fertile, but agricultural ero-sion was a problem and soil-forming processes on theisland were slow compared to more tropical islands.Nutrient input to soils from atmospheric dust from Asiawas not significant.

* The island s three volcanoes are not active, so no freshvolcanic ash added nutrients to the soils. The topographyis low, with gentle slopes. Steep high mountains generateclouds, rain, and runoff that nourish lowlands.

* With a subtropical climate with an annual rainfall of80 cm (50 in.), there was sufficient rainfall, but thewater quickly infiltrated through the soil into porous vol-canic rock.

* There are no coral reefs at Easter Island to provide abun-dant marine resources.

There is fear today that our planet, an isolated island inspace, may be reaching the same threshold faced by thepeople of Easter Island in the sixteenth century. In the twenty-first century, we are facing limitations of our resources in avariety of areas, including soils, fresh water, forests, range-lands, and ocean fisheries. The primary question from bothan environmental perspective and in terms of the history ofhumans on Earth is: Will we recognize the limits of Earth sresources before it is too late to avoid the collapse of humansociety on a global scale? Today, there are no more frontierson Earth, and we have a nearly fully integrated global econ-omy. With our modern technology, we have the ability toextract resources and transform our environment at ratesmuch faster than any people before us. The major lessonfrom Easter Island is clear: Develop a sustainable globaleconomy that ensures the survival of our resource base andother living things on Earth, or suffer the consequences.1

Some aspects of the history of Easter Island have recentlybeen challenged as being only part of the story. Deforesta-tion certainly played a role in the loss of the trees, and ratsthat arrived with the Polynesians were evidently responsiblefor eating the seeds of the palm trees, thus preventing regen-eration. The alternative explanation is that the Polynesianpeople on Easter Island at the time of European contact in1722 numbered about 3000 persons. This population mayhave been close to the maximum reached in about the year1350. Following contact, introduced diseases and enslave-ment resulted in a reduction of the population to about 100by the late 1870s.2 As more of the story of Easter Islandemerges from scientific and social studies, the effects ofhuman resource exploitation, invasive rats, and Europeancontact will become clearer. The environmental lessons of thecollapse will lead to a better understanding of how we cansustain our global human culture.

CASE HISTORY

Easter Island: Are We on the Same Path at a Global Scale?


4 Part 1 Foundations of Environmental Geology

1.1 INTRODUCTION TOENVIRONMENTAL GEOLOGY

Everything has a beginning and an end. Our Earth beganabout 4.6 billion years ago when a cloud of interstellar gasknown as a solar nebula collapsed, forming protostars andplanetary systems (see A Closer Look: Earth s Place in Space).Life on Earth began about 3.5 billion years ago, and, sincethen, multitudes of diverse organisms have emerged,

prospered, and died out, leaving only fossils to mark theirplace in Earth s history. Just a few million years ago, ourancestors set the stage for the present dominance of thehuman species. As certainly as our Sun will die, we, too, willeventually disappear. Viewed in terms of billions of years,our role in Earth s history may be insignificant, but for thoseof us now living, and for our children, our impact on theenvironment is significant, indeed.

A CLOSER LOOK

Earth s Place in SpaceThe famous geologist Preston Cloud wrote:

Born from the wreckage of stars, compressed to a solidstate by the force of its own gravity, mobilized by theheat of gravity and radioactivity, clothed in its filmy gar-ments of air and water by the hot breath of volcanoes,shaped and mineralized by 4.6 billion years of crustalevolution, warmed and peopled by the Sun, thisresilient but finite globe is all our species has to sustainit forever.3

In this short, eloquent statement, Cloud takes us from theorigin of Earth to the concept of sustainability that today isat the forefront of thinking about the environment and ourfuture.

We Have a Right to Be Here The place of humanity inthe universe is stated well in the Desiderata: You are achild of the universe, no less than the trees and the stars;you have the right to be here. And whether or not it isclear to you, no doubt the universe is unfolding as itshould. 4 To some, this might sound a little out of placein science but, as emphasized further by Cloud, peoplecan never escape the fact that we are one piece of thebiosphere, and, although we stand high in it, we are notabove it.3

Origin of the Universe Figure 1.A. presents an idealizedview of the history of the universe, with an emphasis onthe origin of our solar system and Earth. Scientists study-ing the stars and the origin of the universe believe that,about 12 billion years ago, there was a giant explosionknown as the big bang. This explosion produced theatomic particles that later formed galaxies, stars, andplanets. It is believed that, about 7 billion years ago, oneof the first generations of giant stars experienced atremendous explosion known as a supernova. Thisreleased huge amounts of energy, producing a solar neb-ula which is thought to be a spinning cloud of dust andgas. The solar nebula condensed as a result of gravita-tional processes, and our Sun formed at the center, butsome of the particles may have been trapped in solarorbits as rings, similar to those we observe around theplanet Saturn. The density of particles in individual rings

was evidently not constant, so gravitational attraction fromthe largest density of particles in the rings attracted othersuntil they collapsed into the planetary system we havetoday. Thus, the early history of planet Earth, as well asthat of the other planets in our solar system, was character-ized by the intense bombardment of meteorites. This bom-bardment was associated with accretionary processesthat is, the amalgamation of various sized particles, fromdust to meteorites, stony asteroids, and ice-rich cometsmany kilometers in diameter that resulted in the forma-tion of Earth about 4.6 billion years ago.3,5 This is thepart of Earth s history that Cloud refers to when he statesthat Earth was born from the wreckage of stars and com-pressed to a solid state by the force of its own gravity.Heat generated deep within Earth, along with gravita-tional settling of heavier elements such as iron, helped dif-ferentiate the planet into the layered structure we see today(see Chapter 2).

Origin of Atmosphere and Water on Earth Water from ice-cored comets and outgassing, the release of gases such ascarbon dioxide and water vapor from volcanoes and otherprocesses, produced Earth s early atmosphere and water.About 3.5 billion years ago, the first primitive life-formsappeared on Earth in an oxygen-deficient environment.Some of these primitive organisms began producing oxy-gen through photosynthesis, which profoundly affectedEarth s atmosphere. Early primitive, oxygen-producing lifeprobably lived in the ocean, protected from the Sun s ultra-violet radiation. However, as the atmosphere evolved andoxygen increased, an ozone layer was produced in theatmosphere that shielded Earth from harmful radiation.Plants evolved that colonized the land surface, producingforests, meadows, fields, and other environments thatmade the evolution of animal life on the land possible.3

The spiral of life generalized in Figure 1.A delineatesevolution as life changed from simple to complex overseveral billion years of Earth s history. The names of theeras, periods, and epochs that geologists use to dividegeologic time are labeled with their range in millions orbillions of years from the present (Table 1.1). If you go onto study geology, they will become as familiar to you asthe months of the year. The boundaries between eras,



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Geologically speaking, we have been here for a veryshort time. Dinosaurs, for example, ruled the land for morethan 100 million years. Although we do not know how longour own reign will be, the fossil record suggests that allspecies eventually become extinct. How will the history ofour own species unfold, and who will write it? Our hope isto leave something more than some fossils to mark a brieftime when Homo sapiens flourished. Hopefully, as we evolve,we will continue to become more environmentally awareand find ways to live in harmony with our planet.

Geology is the science of processes related to the com-position, structure, and history of Earth and its life. Geol-ogy is an interdisciplinary science, relying on aspects ofchemistry (the composition of Earth s materials), physics(natural laws), and biology (understanding of life-forms).

Environmental geology is applied geology. Specifi-cally, it is the use of geologic information to help us solveconflicts in land use, to minimize environmental degrada-tion, and to maximize the beneficial results of using ournatural and modified environments. The application of

geology to these problems includes the study of the follow-ing (Figure 1.1):

1. Earth materials, such as minerals, rocks, and soils, todetermine how they form, their potential use asresources or waste disposal sites, and their effects onhuman health

2. Natural hazards, such as floods, landslides, earth-quakes, and volcanic activity to minimize loss of lifeand property

3. Land evaluation for site selection, land-use planning,and environmental impact analysis

4. Hydrologic processes of groundwater and surfacewater to evaluate water resources and water pollutionproblems

5. Geologic processes, such as deposition of sediment onthe ocean floor, the formation of mountains, and themovement of water on and below the surface of Earth,to evaluate local, regional, and global change

periods, and epochs are based on both the study of whatwas living at the particular time and on important globalgeologic events in Earth s history. Relative ages of rocksare based on the assemblage of fossils that is, evidenceof past life, such as shells, bones, teeth, leaves, andseeds that are found in rocks or sediments. A generalprinciple of geology, known as the law of faunal assem-blages, states that rocks with similar fossils are most likelyof a similar geologic age. For example, if we find bonesof dinosaurs in a rock, we know the rocks are Mesozoicin age. Fossils provide relative ages of rocks; numerical,or absolute, dates depend upon a variety of sophisticatedchemical age-dating techniques. These age-dating tech-niques allow geologists to often pinpoint the geologicage of rocks containing fossils to within a few millionyears or better.

Evolution as a Process The evolutionary process asdeduced from the fossil record has not been a smooth con-tinuous one but, instead, has been punctuated by explo-sions of new species at some times and extinction of manyspecies at other times. Five mass extinction events areshown in Figure 1.A.

Evolution and extinction of species are natural processes,but, for those times when many species became extinct atapproximately the same time, we use the term mass extinc-tion. For example, the dinosaurs became extinct approxi-mately 65 million years ago. Some geologists believe thismass extinction resulted from climatic and environmentalchanges that naturally occurred on Earth; others believe theplanet was struck by a death star, an asteroid of about10 km (6 mi) in diameter, that crashed into what is today theYucatan Peninsula in Mexico. It is believed that another such

impact would produce firestorms and huge dust clouds thatwould circle Earth in the atmosphere for a prolonged periodof time, blocking out sunlight, greatly reducing or stoppingphotosynthesis, and eventually leading to mass extinction ofboth the species that eat plants and the predators that feedon the plant eaters.5

It is speculated that asteroids of the size that may havecaused the dinosaurs to become extinct are not unique,and such catastrophic impacts have occurred at othertimes during Earth s history. Such an event is the ultimategeologic hazard, the effects of which might result inanother mass extinction, perhaps including humans! (SeeChapter 11.) Fortunately, the probability of such an occur-rence is very small during the next few thousand years. Inaddition, we are developing the technology to identifyand possibly deflect asteroids before they strike Earth. Thehistory of our solar system and Earth, briefly outlinedhere, is an incredible story of planetary and biologicalevolution. What will the future bring? We do not know, ofcourse, but certainly it will be punctuated by a change,and as the evolutionary processes continue, we too willevolve, perhaps to a new species. Through the processesof pollution, agriculture, urbanization, industrialization,and the land clearing of tropical forest, humans appearto be causing an acceleration of the rate of extinction ofplant and animal species. These human activities are sig-nificantly reducing Earth s biodiversity the number andvariability of species over time and space (area) andare thought to be a major environmental problembecause many living things, including humans, on Earthdepend on the environment with its diversity of life-formsfor their existence.



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Earth materialsGravel quarry (1a) and rock quarry (1b)

1.

HazardsFlooding from rivers (2a), earthquake fault (2b),coastal erosion (2c), landslide (2d)

2.

Land-use planning and environmental impactUrban and coastal lands, rivers, and reservoirs (3a e)

3.

Hydrologic processesSurface rivers (4a), and groundwater (4b),water pollution (4c)

4.

FIGURE 1.1 Components of environmental geology Idealized diagram illustrating four main areas of study for environmental geology. Geologicprocesses encompass all of the four areas. These offer employment opportunities for geologists, engineers, and hydrologists.

Considering the breadth of its applications, we can fur-ther define environmental geology as the branch of Earthscience that studies the entire spectrum of human interac-tions with the physical environment. In this context, envi-ronmental geology is a branch of environmental science, thescience of linkages between physical, biological, and socialprocesses in the study of the environment.

1.2 FUNDAMENTAL CONCEPTS OF

ENVIRONMENTAL GEOLOGY

Before we begin to explore the many facets of environmen-tal geology presented in this textbook, there are some basicconcepts that need to be introduced. These five fundamen-tal concepts serve as a conceptual framework upon which



the rest of the textbook will build. As you read throughEnvironmental Geology, you will notice that these conceptsare revisited throughout the text.

1. Human population growth

2. Sustainability

3. Earth as a system

4. Hazardous Earth processes

5. Scientific knowledge and values

The five concepts presented here do not constitute a list of allconcepts that are important to environmental geologists, andthey are not meant to be memorized. However, a generalunderstanding of each concept will help you comprehend andevaluate the material presented in the rest of the text.

Concept One: Human Population GrowthThe number one environmental problem is the increase inhuman population.

The number one environmental problem is the ever-growinghuman population. For most of human history, our numberswere small, as was our input on Earth. With the advent ofagriculture, sanitation, modern medicine, and, especially,inexpensive energy sources such as oil, we have proliferatedto the point where our numbers are a problem. The totalenvironmental impact from people is estimated by theimpact per person times the total number of people. There-fore, as population increases, the total impact must alsoincrease. As population increases, more resources are neededand, given our present technology, greater environmentaldisruption results. When local population density increasesas a result of political upheaval and wars, famine may result(Figure 1.2).

Exponential GrowthWhat Is the Population Bomb? Overpopulation has been aproblem in some areas of the world for at least several hun-dred years, but it is now apparent that it is a global problem.From 1830 to 1930, the worlds population doubled from 1 to2 billion people. By 1970 it had nearly doubled again, and, bythe year 2000, there were about 6 billion people on Earth.The problem is sometimes called the population bomb,because the exponential growth of the human populationresults in the explosive increase in the number of people(Figure 1.3). Exponential growth of humans means that the

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FIGURE 1.2 Famine Korem Camp, Ethiopia, in 1984. Hungry peopleare forced to flee their homes as a result of political and military activityand gather in camps such as these. Surrounding lands may be devas-tated by overgrazing from stock animals, gathering of firewood, and justtoo many people in a confined area. The result may be famine. (DavidBurnett/Contact Press Images, Inc.)

.

FIGURE 1.3 The population bomb The population in 2006is 6.6 billion and growing. (Modified after U.S. Department ofState)



number of people added to the population each year is notconstant; rather, a constant percentage of the current popula-tion is added each year. As an analogy, consider a high-yieldsavings account that pays interest of 7 percent per year. If youstart with $100, at the end of the first year you have $107, andyou earned $7 in interest. At the end of the second year, 7 per-cent of $107 is $7.49, and your balance is $107 plus $7.49, or$114.49. Interest in the third year is 7 percent of 114.49, or$8.01, and your account has $122.51. In 30 years you will havesaved about $800.00. Read on to find out how I know this.

There are two important aspects of exponential growth:

* The growth rate, measured as a percentage

* The doubling time, or the time it takes for whatever isgrowing to double

Figure 1.4 illustrates two examples of exponential growth.In each case, the object being considered (student pay orworld population) grows quite slowly at first, begins toincrease more rapidly, and then continues at a very rapidrate. Even very modest rates of growth eventually producevery large increases in whatever is growing.

How Fast Does Population Double? A general rule isthat doubling time (D) is roughly equal to 70 divided by thegrowth rate (G):

Using this approximation, we find that a population with a 2 percent annual growth rate would double in about 35 years.If it were growing at 1 percent per year, it would double inabout 70 years (see Putting Some Numbers On: ExponentialGrowth ).

Many systems in nature display exponential growth someof the time, so it is important that we be able to recognizesuch growth because it can eventually yield incredibly

D = 70>G

large numbers. As an extreme example of exponential growth(Figure 1.4a), consider the student who, after taking a job for1 month, requests from the employer a payment of 1 cent for the first day of work, 2 cents for the second day, 4 cents forthe third day, and so on. In other words, the payment woulddouble each day. What would be the total? It would take thestudent 8 days to earn a wage of more than $1 per day, and, bythe eleventh day, his earnings would be more than $10 perday. Payment for the 16th day of the month would be morethan $300, and, on the last day of the 31-day month, the stu-dent s earnings for that one day would be more than $10 mil-lion! This is an extreme case because the constant rate ofincrease is 100 percent per day, but it shows that exponentialgrowth is a very dynamic process. The human populationincreases at a much lower rate 1.2 percent per year todaybut even this slower exponential growth eventually results ina dramatic increase in numbers (Figure 1.4b). Exponentialgrowth will be discussed further under Concept Three, whenwe consider systems and change.

Human Population through HistoryWhat Is Our History of Population Growth? The storyof human population increase is put in historic perspective inTable 1.2. When we were hunter-gatherers, our numberswere very small, and growth rates were very low. With agri-culture, growth rates in human population increased by sev-eral hundred times, owing to a stable food supply. During theearly industrial period, (A.D. 1600 to 1800), growth ratesincreased again by about 10 times. With the Industrial Revo-lution, with modern sanitation and medicine, the growthrates increased another 10 times. Human population reached6 billion in 2000. By 2013, it will be 7 billion, and, by 2050, itwill be about 9 billion. That is 1 billion new people in only13 years and 3 billion (about one-half of today s population)

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FIGURE 1.4 Exponential growth (a) Example of a student spay, beginning at 1 cent for the first day of work and doublingdaily for 31 days. (b) World population. Notice that both curveshave the characteristic J shape, with a slow initial increase fol-lowed by a rapid increase. The actual shape of the curvedepends on the scale at which the data are plotted. It often lookslike the tip of a skateboard. (Population data from U.S. Depart-ment of State)



PUT TING SOME NUMBERS ON

Exponential GrowthExponential growth is a powerful process related topositive feedback, where the quantity of what is beingevaluated (for example, human population increase, con-sumption of resources such as oil or minerals, or rate ofland converted to urban purposes) grow at a fixed rate (apercentage) per year. Exponential growth of the humanpopulation is shown in Figure 1.4.

Calculating exponential growth is surprisingly easy andinvolves a rather simple equation:

where N is the future value of whatever is being evaluated;N0 is present value; e is a constant 2.71828; k is equal tothe rate of increase (a decimal representing a percentage);and t is the number of years over which the growth is to becalculated. Growth rate R is defined as the percent changeper unit of time: This equation may be solvedutilizing a simple hand calculator, and a number of interest-ing environmental questions may be asked as a result. Forexample, assume that we wanted to know what the worldpopulation is going to be in the year 2020, given that thepopulation in 2000 is 6.1 billion and the population is grow-ing at a constant rate of 1.2 percent per year (0.012 as adecimal). Precise figures of human population and growthrates may be obtained from a variety of sources, includingthe U.S. Bureau of Census. Assuming that world populationwas 6.1 billion in the year 2000 and that the growth rate is1.2 percent per year, we can estimate the world populationfor the year 2020 by applying the equation above:

Our equation for exponential growth may also berearranged to project the time in the future when the earthwill reach a certain population. In this case, we mustassume a beginning population, a population at some timein the future, and the growth rate. Thus, t may be solved bythe following equation:

where all the terms have been defined and ln is the naturallogarithm to the base 2.71828. If we use our previous example

t = 11>k2 ln1N>N02

the above assumptions2or 7.75 billion persons.year 2020 based upon

= 7.75 * 109,N 1population projected to

12.718280.242

= 16.1 * 1092

N = 16.1 * 10921e0.242

= 16.1 * 10921e10.012 * 2022N 1world population in 20202

K = R>100.

N = N0 ekt

and pose the question that, if the population growth remains

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