1.2 Contents

   Meet the Authors vii

   Preface xix

   Chapter 1

The Earth System 3

   The Scientific Method 4

   Geology as a Science 5

   Earth’s Shape and Surface 8

   Peeling the Onion: Discovery of a Layered Earth 9

      Earth’s Density 10

      The Mantle and Core 10

      The Crust 11

      The Inner Core 11

      Chemical Composition of Earth’s Major Layers 12

   Earth as a System of Interacting Components 13

      The Climate System 15

      The Plate Tectonic System 16

      The Geodynamo 17

      Interactions Among Geosystems Support Life 18

   An Overview of Geologic Time 18

      The Origin of Earth and Its Global Geosystems 19

      The Evolution of Life 19

   Welcome to Google Earth 21

Chapter 2

Plate Tectonics: The Unifying Theory 27

   The Discovery of Plate Tectonics 28

      Continental Drift 28

      Seafloor Spreading 29

      The Great Synthesis: 1963—1968 30

   The Plates and Their Boundaries 31

      Divergent Boundaries 36

      Convergent Boundaries 36

      Transform Faults 38

      Combinations of Plate Boundaries 38

   Rates and History of Plate Movements 39

      The Seafloor as a Magnetic Tape Recorder 39

      Deep-Sea Drilling 41

      Measurements of Plate Movements by Geodesy 41

   The Grand Reconstruction 42

      Seafloor Isochrons 43

      Reconstructing the History of Plate Movements 43

      The Breakup of Pangaea 44

      The Assembly of Pangaea by Continental Drift 44

      Implications of the Grand Reconstruction 44

   Mantle Convection: The Engine of Plate Tectonics 45

      Where Do the Plate-Driving Forces Originate? 45

684

      How Deep Does Plate Recycling Occur? 48

      What Is the Nature of Rising Convection Currents? 49

   The Theory of Plate Tectonics and the Scientific Method 52

Chapter 3

Earth Materials: Minerals and Rocks 57

   What Are Minerals? 58

   The Structure of Matter 59

      The Structure of Atoms 59

      Atomic Number and Atomic Mass 59

      Chemical Reactions 60

      Chemical Bonds 61

   The Formation of Minerals 61

      The Atomic Structure of Minerals 61

      The Crystallization of Minerals 62

      How Do Minerals Form? 63

   Classes of Rock-Forming Minerals 64

      Silicates 65

      Carbonates 67

      Oxides 67

      Sulfides 67

      Sulfates 68

   Physical Properties of Minerals 69

      Hardness 69

      Cleavage 70

      Fracture 71

      Luster 71

      Color 72

      Density 73

      Crystal Habit 73

   What Are Rocks? 74

      Properties of Rocks 74

      Igneous Rocks 76

      Sedimentary Rocks 77

      Metamorphic Rocks 78

   The Rock Cycle: Interactions Between the Plate Tectonic and Climate Systems 79

   Concentrations of Valuable Mineral Resources 81

      Hydrothermal Deposits 82

      Igneous Deposits 83

      Sedimentary Deposits 84

Chapter 4

Igneous Rocks: Solids from Melts 91

   How Do Igneous Rocks Differ from One Another? 92

      Texture 92

      Chemical and Mineral Composition 94

   How Do Magmas Form? 97

      How Do Rocks Melt? 97

      The Formation of Magma Chambers 99

      Where Do Magmas Form? 99

   Magmatic Differentiation 99

      Fractional Crystallization: Laboratory and Field Observations 99

      Granite from Basalt: Complexities of Magmatic Differentiation 101

   Forms of Igneous Intrusions 102

      Plutons 103

      Sills and Dikes 103

      Veins 105

   Igneous Processes and Plate Tectonics 105

      Spreading Centers as Magma Factories 106

      Subduction Zones as Magma Factories 108

      Mantle Plumes as Magma Factories 111

Chapter 5

Sedimentation: Rocks Formed by Surface Processes 115

   Surface Processes of the Rock Cycle 116

      Weathering and Erosion: The Source of Sediments 117

      Transportation and Deposition: The Downhill Journey to Sedimentary Basins 119

      Oceans as Chemical Mixing Vats 122

   Sedimentary Basins: The Sinks for Sediments 122

      Rift Basins and Thermal Subsidence Basins 122

      Flexural Basins 123

   Sedimentary Environments 124

      Continental Sedimentary Environments 124

      Shoreline Sedimentary Environments 124

      Marine Sedimentary Environments 124

      Siliciclastic versus Chemical and Biological Sedimentary Environments 126

   Sedimentary Structures 127

      Cross-Bedding 127

      Graded Bedding 127

      Ripples 128

      Bioturbation Structures 128

      Bedding Sequences 129

   Burial and Diagenesis: From Sediment to Rock 130

      Burial 130

      Diagenesis 130

   Classification of Siliciclastic Sediments and Sedimentary Rocks 132

      Coarse-Grained Siliciclastics: Gravel and Conglomerate 133

685

      Medium-Grained Siliciclastics: Sand and Sandstone 133

      Fine-Grained Siliciclastics 134

   Classification of Chemical and Biological Sediments and Sedimentary Rocks 135

      Carbonate Sediments and Rocks 136

      Evaporite Sediments and Rocks: Products of Evaporation 140

      Other Biological and Chemical Sediments 142

Chapter 6

Metamorphism: Alteration of Rocks by Temperature and Pressure 149

   Causes of Metamorphism 150

      The Role of Temperature 151

      The Role of Pressure 152

      The Role of Fluids 153

   Types of Metamorphism 153

      Regional Metamorphism 154

      Contact Metamorphism 154

      Seafloor Metamorphism 154

      Other Types of Metamorphism 154

   Metamorphic Textures 155

      Foliation and Cleavage 155

      Foliated Rocks 155

      Granoblastic Rocks 157

      Porphyroblasts 158

   Regional Metamorphism and Metamorphic Grade 159

      Mineral Isograds: Mapping Zones of Change 159

      Metamorphic Grade and Parent Rock Composition 160

      Metamorphic Facies 161

   Plate Tectonics and Metamorphism 162

      Metamorphic Pressure-Temperature Paths 162

      Ocean-Continent Convergence 163

      Continent-Continent Collision 165

      Exhumation: A Link Between the Plate Tectonic and Climate Systems 166

Chapter 7

Deformation: Modification of Rocks by Folding and Fracturing 171

   Plate Tectonic Forces 172

   Mapping Geologic Structure 172

      Measuring Strike and Dip 173

      Geologic Maps 173

      Geologic Cross Sections 175

   How Rocks Deform 175

      Brittle and Ductile Behavior of Rocks in the Laboratory 175

      Brittle and Ductile Behavior of Rocks in Earth’s Crust 176

   Basic Deformation Structures 177

      Faults 177

      Folds 179

      Circular Structures 182

      Joints 183

      Deformation Textures 183

   Styles of Continental Deformation 184

      Tensional Tectonics 184

      Compressive Tectonics 185

      Shearing Tectonics 187

   Unraveling Geologic History 188

Chapter 8

Clocks in Rocks: Timing the Geologic Record 195

   Reconstructing Geologic History from the Stratigraphic Record 196

      Principles of Stratigraphy 197

      Fossils as Recorders of Geologic Time 198

      Unconformities: Gaps in the Geologic Record 200

      Cross-Cutting Relationships 201

   The Geologic Time Scale: Relative Ages 202

      Intervals of Geologic Time 202

      Interval Boundaries Mark Mass Extinctions 202

      Ages of Petroleum Source Rocks 206

   Measuring Absolute Time with Isotopic Clocks 207

      Discovery of Radioactivity 208

      Radioactive Isotopes: The Clocks in Rocks 208

      Isotopic Dating Methods 209

   The Geologic Time Scale: Absolute Ages 210

      Eons: The Longest Intervals of Geologic Time 210

      Perspectives on Geologic Time 211

   Recent Advances in Timing the Earth System 212

      Sequence Stratigraphy 212

      Chemical Stratigraphy 213

      Paleomagnetic Stratigraphy 213

      Clocking the Climate System 213

686

Chapter 9

Early History of the Terrestrial Planets 221

   Origin of the Solar System 222

      The Nebular Hypothesis 222

      The Sun Forms 223

      The Planets Form 223

      Small Bodies of the Solar System 224

   Early Earth: Formation of a Layered Planet 225

      Earth Heats Up and Melts 225

      Differentiation of Earth’s Core, Mantle, and Crust 226

      Earth’s Oceans and Atmosphere Form 227

   Diversity of the Planets 228

   What’s in a Face? The Age and Complexion of Planetary Surfaces 230

      The Man in the Moon: A Planetary Time Scale 230

      Mercury: The Ancient Planet 231

      Venus: The Volcanic Planet 233

      Mars: The Red Planet 235

      Earth: No Place Like Home 236

   Mars Rocks! 237

      Missions to Mars: Flybys, Orbiters, Landers, and Rovers 238

      Mars Exploration Rovers: Spirit and Opportunity 240

      Mars Science Laboratory (MSL): Curiosity 240

      Recent Missions: Mars Reconnaissance Orbiter and Phoenix 243

      Recent Discoveries: The Environmental Evolution of Mars 243

   Exploring the Solar System and Beyond 245

      Space Missions 245

      The Cassini-Huygens Mission to Saturn 246

      Other Solar Systems 248

Chapter 10

History of the Continents 253

   The Structure of North America 254

      The Stable Interior 254

      The Appalachian Fold Belt 256

      The Coastal Plain and Continental Shelf 256

      The North American Cordillera 257

   Tectonic Provinces Around the World 259

      Types of Tectonic Provinces 260

      Tectonic Ages 261

      A Global Puzzle 262

   How Continents Grow 262

      Magmatic Addition 262

      Accretion 263

   How Continents Are Modified 266

      Orogeny: Modification by Plate Collision 266

      The Wilson Cycle 271

      Epeirogeny: Modification by Vertical Movements 272

   The Origins of Cratons 273

   The Deep Structure of Continents 276

      Cratonic Keels 276

      Composition of the Keels 277

      Age of the Keels 278

Chapter 11

Geobiology: Life Interacts with Earth 283

   The Biosphere as a System 284

      Ecosystems 284

      Inputs: The Stuff Life Is Made Of 285

      Processes and Outputs: How Organisms Live and Grow 286

      Biogeochemical Cycles 288

   Microorganisms: Nature’s Tiny Chemists 288

      Abundance and Diversity of Microorganisms 289

      Microorganism-Mineral Interactions 292

   Geobiologic Events in Earth’s History 296

      Origin of Life and the Oldest Fossils 296

      Prebiotic Soup: The Original Experiment on the Origin of Life 297

      The Oldest Fossils and Early Life 298

      Origin of Earth’s Oxygenated Atmosphere 299

   Evolutionary Radiations and Mass Extinctions 300

      Radiation of Life: The Cambrian Explosion 301

      Tail of the Devil: The Demise of Dinosaurs 303

      Global Warming Disaster: The Paleocene-Eocene Mass Extinction 304

   Astrobiology: The Search for Extraterrestrial Life 306

      Habitable Zones Around Stars 307

      Habitable Environments on Mars 308

Chapter 12

Volcanoes 313

   Volcanoes as Geosystems 314

   Lavas and Other Volcanic Deposits 315

      Types of Lava 315

      Textures of Volcanic Rocks 319

      Pyroclastic Deposits 319

687

   Eruptive Styles and Landforms 320

      Central Eruptions 321

      Fissure Eruptions 325

   Interactions of Volcanoes with Other Geosystems 326

      Volcanism and the Hydrosphere 327

      Volcanism and the Atmosphere 328

   The Global Pattern of Volcanism 329

      Volcanism at Spreading Centers 330

      Volcanism in Subduction Zones 330

      Intraplate Volcanism: The Mantle Plume Hypothesis 331

   Volcanism and Human Affairs 334

      Volcanic Hazards 334

      Reducing the Risks of Volcanic Hazards 337

      Natural Resources from Volcanoes 339

Chapter 13

Earthquakes 347

   What Is an Earthquake? 348

      The Elastic Rebound Theory 349

      Fault Rupture During Earthquakes 351

      Foreshocks and Aftershocks 351

   How Do We Study Earthquakes? 353

      Seismographs 354

      Seismic Waves 355

      Locating the Focus 357

      Measuring the Size of an Earthquake 357

      Determining Fault Mechanisms 361

      GPS Measurements and “Silent” Earthquakes 362

   Earthquakes and Patterns of Faulting 362

      The Big Picture: Earthquakes and Plate Tectonics 362

      Regional Fault Systems 364

   Earthquake Hazards and Risks 365

      How Earthquakes Cause Damage 366

      Reducing Earthquake Risk 369

   Can Earthquakes Be Predicted? 375

      Long-Term Forecasting 375

      Short-Term Prediction 375

      Medium-Term Forecasting 376

Chapter 14

Exploring Earth’s Interior 383

   Exploring Earth’s Interior with Seismic Waves 384

      Basic Types of Waves 384

      Paths of Seismic Waves Through Earth 384

      Seismic Exploration of Near-Surface Layering 387

   Layering and Composition of Earth’s Interior 388

      The Crust 388

      The Mantle 388

      The Core-Mantle Boundary 390

      The Core 390

   Earth’s Internal Temperature 390

      Heat Flow Through Earth’s Interior 390

      Temperatures Inside Earth 392

   Visualizing Earth’s Three-Dimensional Structure 394

      Seismic Tomography 394

      Earth’s Gravitational Field 396

   Earth’s Magnetic Field and The Geodynamo 396

      The Dipole Field 396

      Complexity of the Magnetic Field 396

      Paleomagnetism 400

      The Magnetic Field and the Biosphere 402

Chapter 15

The Climate System 407

   Components of the Climate System 408

      The Atmosphere 408

      The Hydrosphere 409

      The Cryosphere 411

      The Lithosphere 411

      The Biosphere 412

   The Greenhouse Effect 413

      A Planet Without Greenhouse Gases 413

      Earth’s Greenhouse Atmosphere 414

      Balancing the Climate System Through Feedbacks 414

      Climate Models and Their Limitations 415

   Climate Variation 416

      Short-Term Regional Variations 417

      Long-Term Global Variations: The Pleistocene Ice Ages 417

      Long-Term Global Variations: Paleozoic and Proterozoic Ice Ages 422

      Variations During the Most Recent Glacial Cycle 422

   The Carbon Cycle 423

      Geochemical Cycles and How They Work 423

      The Cycling of Carbon 426

      Human Perturbations of the Carbon Cycle 427

   Twentieth-Century Warming: Fingerprints of Anthropogenic Global Change 428

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Chapter 16

Weathering, Erosion, and Mass Wasting: Interactions Between the Climate and Plate Tectonic Systems 435

   Weathering, Erosion, Mass Wasting, and the Rock Cycle 436

   Controls on Weathering 436

      The Properties of Parent Rock 436

      Climate: Rainfall and Temperature 437

      The Presence or Absence of Soil 437

      The Length of Exposure 437

   Chemical Weathering 438

      The Role of Water: Feldspar and Other Silicates 438

      Carbon Dioxide, Weathering, and the Climate System 439

      The Role of Oxygen: From Iron Silicates to Iron Oxides 441

      Chemical Stability 442

   Physical Weathering 443

      How Do Rocks Break? 443

      Interactions Between Weathering and Erosion 444

   Soils: The Residue of Weathering 445

      Soils as Geosystems 446

      Paleosols: Working Backward from Soil to Climate 447

   Mass Wasting 447

      Slope Materials 449

      Water Content 450

      Slope Steepness 451

      Triggers of Mass Movements 452

   Classification of Mass Movements 453

      Mass Movements of Rock 455

      Mass Movements of Unconsolidated Material 456

   Understanding the Origins of Mass Movements 460

      Natural Causes of Mass Movements 461

      Human Activities That Promote or Trigger Mass Movements 462

Chapter 17

The Hydrologic Cycle and Groundwater 469

   The Geologic Cycling of Water 470

      Flow and Reservoirs 470

      How Much Water Is There? 470

      The Hydrologic Cycle 470

      How Much Water Can We Use? 471

   Hydrology and Climate 472

      Humidity, Rainfall, and Landscape 472

      Droughts 473

      The Hydrology of Runoff 475

   The Hydrology of Groundwater 477

      Porosity and Permeability 478

      The Groundwater Table 480

      Aquifers 482

      Balancing Recharge and Discharge 482

      The Speed of Groundwater Flows 485

      Groundwater Resources and Their Management 485

   Erosion by Groundwater 488

   Water Quality 490

      Contamination of the Water Supply 490

      Reversing Contamination 491

      Is the Water Drinkable? 491

   Water Deep in the Crust 492

      Hydrothermal Waters 492

      Ancient Microorganisms in Deep Aquifers 494

Chapter 18

Stream Transport: From Mountains to Oceans 499

   The Form of Streams 500

      Stream Valleys 500

      Channel Patterns 500

      Stream Floodplains 503

      Drainage Basins 503

      Drainage Networks 505

      Drainage Patterns and Geologic History 505

   Where Do Channels Begin? How Running Water Erodes Soil and Rock 507

      Abrasion 508

      Chemical and Physical Weathering 508

      The Undercutting Action of Waterfalls 508

   How Currents Flow and Transport Sediment 509

      Erosion and Sediment Transport 510

      Sediment Bed Forms: Dunes and Ripples 511

   Deltas: The Mouths of Rivers 513

      Delta Sedimentation 513

      The Growth of Deltas 513

      Human Effects on Deltas 515

      The Effects of Ocean Currents, Tides, and Plate Tectonic Processes 515

   Streams as Geosystems 515

      Discharge 516

      Floods 518

      Longitudinal Profiles 519

      Lakes 522

689

Chapter 19

Winds and Deserts 529

   Global Wind Patterns 530

   Wind as a Transport Agent 531

      Wind Strength 531

      Particle Size 531

      Surface Conditions 531

      Materials Carried by Wind 531

   Wind as an Agent of Erosion 534

      Sandblasting 534

      Deflation 534

   Wind as a Depositional Agent 535

      Where Sand Dunes Form 535

      How Sand Dunes Form and Move 536

      Dune Types 538

      Dust Falls and Loess 538

   The Desert Environment 540

      Where Deserts Are Found 540

      Desert Weathering and Erosion 542

      Desert Sediments and Sedimentation 543

      Desert Landscapes 544

Chapter 20

Coastlines and Ocean Basins 551

   How Ocean Basins Differ from Continents 552

   Coastal Processes 552

      Wave Motion: The Key to Shoreline Dynamics 553

      The Surf Zone 554

      Wave Refraction 555

      Tides 556

      Hurricanes and Coastal Storm Surges 557

   The Shaping of Shorelines 564

      Beaches 564

      Erosion and Deposition at Shorelines 567

      Effects of Sea Level Change 568

   Continental Margins 570

      The Continental Shelf 571

      The Continental Slope and Rise 571

      Submarine Canyons 571

   Topography of the Deep Seafloor 572

      Probing the Seafloor from Surface Ships 572

      Charting the Seafloor by Satellite 575

      Profiles Across Two Oceans 575

      Main Features of the Deep Seafloor 578

   Ocean Sedimentation 578

      Sedimentation on the Continental Shelf 579

      Deep-Sea Sedimentation 579

Chapter 21

Glaciers: The Work of Ice 587

   Ice as a Rock 588

      Valley Glaciers 588

      Continental Glaciers 590

   How Glaciers Form 591

      Basic Ingredients: Freezing Cold and Lots of Snow 591

      Glacial Growth: Accumulation 592

      Glacial Shrinkage: Ablation 592

      The Glacial Budget: Accumulation Minus Ablation 592

   How Glaciers Move 594

      Mechanisms of Glacial Flow 594

      Flow in Valley Glaciers 594

      Antarctica in Motion 594

   Glacial Landscapes 598

      Glacial Erosion and Erosional Landforms 599

      Glacial Sedimentation and Sedimentary Landforms 603

      Permafrost 606

   Glacial Cycles and Climate Change 606

      The Wisconsin Glaciation 607

      Glaciation and Sea Level Change 608

      The Geologic Record of Pleistocene Glaciations 609

      The Geologic Record of Ancient Glaciations 609

Chapter 22

Landscape Development 617

   Topography, Elevation, and Relief 618

   Landforms: Features Sculpted by Erosion and Sedimentation 621

      Mountains and Hills 621

      Plateaus 623

      Stream Valleys 623

      Structurally Controlled Ridges and Valleys 626

      Structurally Controlled Cliffs 626

   How Interacting Geosystems Control Landscapes 626

      Feedback Between Climate and Topography 628

      Feedback Between Uplift and Erosion 629

   Models of Landscape Development 630

      Davis’s Cycle: Uplift Is Followed by Erosion 632

      Penck’s Model: Erosion Competes with Uplift 634

      Hack’s Model: Erosion and Uplift Achieve Equilibrium 636

690

Chapter 23

The Human Impact on Earth’s Environment 641

   Civilization as a Global Geosystem 642

      Natural Resources 642

      Energy Resources 643

      Rise of the Carbon Economy 644

      Global Energy Consumption 645

      Energy Resources for the Future 646

      Carbon Flux from Energy Production 646

   Fossil-Fuel Resources 646

      How Do Oil and Gas Form? 647

      Where Do We Find Oil and Gas? 647

      Distribution of Oil Reserves 648

      Oil Production and Consumption 649

      When Will We Run Out of Oil? 650

      Oil and the Environment 650

      Natural Gas 651

      Coal 653

      Unconventional Hydrocarbon Resources 655

   Alternative Energy Resources 655

      Nuclear Energy 655

      Biofuels 657

      Solar Energy 658

      Hydroelectric Energy 658

      Wind Energy 658

      Geothermal Energy 660

   Global Change 660

      Greenhouse Gases and Global Warming 660

      Predictions of Future Global Warming 661

      Consequences of Climate Change 662

      Ocean Acidification 666

      Loss of Biodiversity 666

   Earth System Engineering and Management 667

      Energy Policy 668

      Use of Alternative Energy Resources 669

      Engineering the Carbon Cycle 669

      Stabilizing Carbon Emissions 669

      Sustainable Development 670

   Appendix 1 Conversion Factors AP—1

   Appendix 2 Numerical Data Pertaining to Earth AP—2

   Appendix 3 Chemical Reactions AP—3

   Appendix 4 Properties of the Most Common Minerals of Earth’s Crust AP—5

   Appendix 5 Practicing Geology Exercises: Answers to Problems AP—9

      Glossary G—1

      Index I—1

691