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
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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
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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
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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
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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
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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
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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
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