About the Authors ii Preface x The Learning System xii Chapter 1 Introduction to Physical Geology 2 Who Needs Geology? 4 Avoiding Geologic Hazards 6 Supplying Things We Need 7 Protecting the Environment 8 Understanding Our Surroundings 11 An Overview of Physical Geology-Important Concepts 11 Internal Processes: How the Earth's Internal Heat Engine Works 14 The Earth's Interior 15 The Theory of Plate Tectonics 16 Surficial Processes: The Earth's External Heat Engine 18 Geologic Time 21 Summary 22 Terms to Remember 22 Testing Your Knowledge 23 Expanding your Knowledge 24 Exploring Resources 24 Interacting with Journey Through Geology CD-ROM 25 Chapter 2 Atoms, Elements, and Minerals 26 Atoms and Elements 28 Chemical Activity 30 Ions 30 Chemical Composition of the Earth's Crust 31 Crystallinity 32 The Silicon-Oxygen Tetrahedron 33 Minerals 37 Crystalline Solids 37 Natural and Inorganic Substances 37 Definite Chemical Composition 37 The Important Minerals 38 The Physical Properties of Minerals 40 Color 40 Streak 40 Luster 40 Hardness 40 External Crystal Form 41 Cleavage 43 Fracture 45 Specific Gravity 45 Other Properties 46 Simple Chemical Tests 46 The Rock Cycle 47 Summary 49 Chapter 3 Igneous Rocks, Intrusive Activity, and the Origin of Igneous Rocks 52 Igneous Rocks 55 Identification of Igneous Rocks 55 Varieties of Granite 58 Chemistry of Igneous Rocks 58 Intrusive Bodies 59 Shallow Intrusive Structures 60 Intrusives That Crystallize at Depth 61 Abundance and Distribution of Plutonic Rocks 63 How Magma Forms 63 Heat for Melting Rock 64 Factors That Control Melting Temperatures 64 How Magmas of Different Compositions Evolve 66 Differentiation and Bowen's Reaction Theory 66 Partial Melting 68 Assimilation 69 Mixing of Magmas 69 Explaining Igneous Activity by Plate Tectonics 70 Igneous Processes at Divergent Boundaries 70 Intraplate Igneous Activity 70 Igneous Processes at Convergent Boundaries 71 Summary 73 Chapter 4 Volcanism and Extrusive Rocks 76 Effects on Humans 78 The Growth of Hawaii 78 Geothermal Energy 78 Effect on Climate 78 Volcanic Catastrophes 81 Eruptive Violence and Physical Characteristics of Lava 82 Extrusive Rocks and Gases 83 Scientific Investigation of Volcanism 83 Gases 84 Extrusive Rocks 84 Types of Volcanoes 87 Shield Volcanoes 88 Cinder Cones 88 Composite Volcanoes 90 Volcanic Domes 93 Lava Floods 95 Submarine Eruptions 96 Pillow Basalts 97 Summary 99 Chapter 5 Weathering and Soil 102 Weathering, Erosion, and Transportation 104 How Weathering Alters Rocks 104 Effects of Weathering 104 Mechanical Weathering 104 Frost Action 104 Abrasion 106 Pressure Release 107 Chemical Weathering 108 Role of Oxygen 108 Role of Acid 109 Solution Weathering 110 Chemical Weathering of Feldspar 111 Chemical Weathering of Other Minerals 112 Weathering and Climate 113 Weathering Products 113 Soil 113 Soil Horizons 114 Residual and Transported Soils 114 Soils, Parent Rock, Time, and Slope 115 Organic Activity 116 Soils and Climate 116 Buried Soils 117 Summary 118 Chapter 6 Sediments and Sedimentary Rocks 120 Sediment 122 Transportation 122 Deposition 123 Preservation 124 Lithification 125 Types of Sedimentary Rocks 126 Clastic Rocks 126 Breccia and Conglomerate 126 Sandstone 127 The Fine-Grained Rocks 128 Chemical Sedimentary Rocks 130 Carbonate Rocks 130 Chert 133 Evaporites 134 Organic Sedimentary Rocks 135 Coal 135 The Origin of Oil and Gas 135 Sedimentary Structures 135 Formations 139 Interpretation of Sedimentary Rocks 140 Source Area 140 Environment of Deposition 142 Plate Tectonics and Sedimentary Rocks 145 Summary 146 Chapter 7 Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks 150 Factors Controlling the Characteristics of Metamorphic Rocks 152 Composition of the Parent Rock 152 Temperature 153 Pressure 153 Fluids 155 Time 156 Classification of Metamorphic Rocks 156 Types of Metamorphism 156 Contact Metamorphism 156 Regional Metamorphism 158 Plate Tectonics and Metamorphism 162 Hydrothermal Processes 163 Hydrothermal Activity at Diverging Plate Boundaries 163 Metasomatism 165 Hydrothermal Rocks and Minerals 166 Sources of Water 167 Summary 169 Chapter 8 Time and Geology 172 The Key to the Past 174 Relative Time 174 Principles Used to Determine Relative Age 174 Correlation 179 The Standard Geologic Time Scale 182 Unconformities 183 Disconformities 183 Angular Unconformities 185 Nonconformities 186 Absolute Age 186 Isotopic Dating 186 Uses of Isotopic Dating 189 Combining Relative and Absolute Ages 190 Age of the Earth 191 Comprehending Geologic Time 191 Summary 195 Chapter 9 Mass Wasting 198 Classification of Mass Wasting 200 Rate of Movement 200 Type of Material 200 Type of Movement 202 Controlling Factors in Mass Wasting 203 Gravity 204 Water 204 Common Types of Mass Wasting 205 Creep 205 Debris Flow 206 Rockfalls and Rockslides 212 Preventing Landslides 215 Preventing Mass Wasting of Debris 215 Preventing Rockfalls and Rockslides on Highways 216 Summary 218 Chapter 10 Streams and Floods 220 The Hydrologic Cycle 222 Channel Flow and Sheet Flow 222 Drainage Basins 224 Drainage Patterns 224 Factors Affecting Stream Erosion and Deposition 225 Velocity 225 Gradient 226 Channel Shape and Roughness 226 Discharge 227 Stream Erosion 228 Stream Transportation of Sediment 229 Stream Deposition 230 Bars 230 Braided Streams 231 Meandering Streams and Point Bars 235 Flood Plains 237 Deltas 239 Alluvial Fans 241 Flooding 242 Urban Flooding 242 Flash Floods 245 Controlling Floods 246 The Great Flood of 1993 247 Stream Valley Development 248 Downcutting and Base Level 248 The Concept of a Graded Stream 250 Lateral Erosion 251 Headward Erosion and Stream Piracy 251 Stream Terraces 252 Incised Meanders 253 Superposed Streams 255 Summary 255 Chapter 11 Ground Water 258 Porosity and Permeability 260 The Water Table 260 The Movement of Ground Water 262 Aquifers 263 Wells 264 Springs and Streams 266 Pollution of Ground Water 266 Balancing Withdrawal and Recharge 272 Effects of Ground-Water Action 274 Caves, Sinkholes, and Karst Topography 274 Other Effects 276 Hot Water Underground 277 Geothermal Energy 278 Summary 278 Chapter 12 Glaciers and Glaciation 282 The Theory of Glacial Ages 284 Glaciers-Where They Are, How They Form and Move 284 Distribution of Glaciers 284 Types of Glaciers 285 Formation and Growth of Glaciers 285 Movement of Valley Glaciers 288 Movement of Ice Sheets 293 Glacial Erosion 294 Erosional Landscapes Associated with Alpine Glaciation 295 Erosional Landscapes Associated with Continental Glaciation 298 Glacial Deposition 299 Moraines 300 Outwash 302 Glacial Lakes and Varves 303 Effects of Past Glaciation 303 The Glacial Ages 303 Direct Effects of Past Glaciation in North America 305 Indirect Effects of Past Glaciation 310 Evidence for Older Glaciation 310 Summary 311 Chapter 13 Deserts and Wind Action 314 Distribution of Deserts 316 Some Characteristics of Deserts 316 Desert Features in the Southwestern United States 319 Wind Action 322 Wind Erosion and Transportation 324 Wind Deposition 327 Summary 332 Chapter 14 Waves, Beaches, and Coasts 336 Water Waves 338 Surf 339 Nearshore Circulation 340 Wave Refraction 340 Longshore Currents 340 Rip Currents 341 Beaches 341 Longshore Drift of Sediment 342 Human Interference with Sand Drift 344 Sources of Sand on Beaches 344 Coasts and Coastal Features 344 Erosional Coasts 345 Depositional Coasts 348 Drowned Coasts 349 Uplifted Coasts 352 Coasts Shaped by Organisms 352 Summary 353 Chapter 15 Geologic Structures 356 Tectonic Forces at Work 358 Stress and Strain in the Earth's Crust 358 Behavior of Rocks to Stress and Strain 359 Present Deformation of the Crust 360 Structures as a Record of the Geologic Past 361 Geologic Maps and Field Methods 361 Folds 363 Geometry of Folds 363 Interpreting Folds 366 Fractures in Rock 367 Joints 368 Faults 370 Summary 379 Chapter 16 Earthquakes 382 Causes of Earthquakes 384 Seismic Waves 386 Body Waves 386 Surface Waves 386 Locating and Measuring Earthquakes 386 Determining the Location of an Earthquake 389 Measuring the Size of an Earthquake 390 Location and Size of Earthquakes in the United States 393 Effects of Earthquakes 395 Tsunamis 399 World Distribution of Earthquakes 401 First-Motion Studies of Earthquakes 404 Earthquakes and Plate Tectonics 404 Earthquakes at Plate Boundaries 405 Subduction Angle 408 Earthquake Prediction 408 Earthquake Control 409 Summary 411 Chapter 17 The Earth's Interior 414 Evidence from Seismic Waves 416 The Earth's Internal Structure 417 The Earth's Crust 418 The Mantle 418 The Core 420 Isostasy 423 Gravity Measurements 425 The Earth's Magnetic Field 427 Magnetic Reversals 428 Magnetic Anomalies 429 Heat Within the Earth 432 Geothermal Gradient 432 Heat Flow 433 Summary 433 Chapter 18 The Sea Floor 436 Origin of the Ocean 438 Methods of Studying the Sea Floor 439 Features of the Sea Floor 440 Continental Shelves and Continental Slopes 440 Submarine Canyons 442 Turbidity Currents 443 Passive Continental Margins 443 The Continental Rise 443 Abyssal Plains 444 Active Continental Margins 444 Oceanic Trenches 445 The Mid-Oceanic Ridge 445 Geologic Activity on the Ridge 446 Biologic Activity on the Ridge 446 Fracture Zones 449 Seamounts, Guyots, and Aseismic Ridges 449 Reefs 450 Sediments of the Sea Floor 452 Oceanic Crust and Ophiolites 452 The Age of the Sea Floor 454 The Sea Floor and Plate Tectonics 455 Summary 455 Chapter 19 Plate Tectonics 458 The Early Case for Continental Drift 460 Skepticism about Continental Drift 462 Paleomagnetism and the Revival of Continental Drift 463 Recent Evidence for Continental Drift 464 History of Continental Positions 465 Sea-Floor Spreading 465 Hess's Driving Force 466 Explanations 466 Plates and Plate Motion 467 How Do We Know That Plates Move? 468 Marine Magnetic Anomalies 468 Another Test: Fracture Zones and Transform Faults 471 Measuring Plate Motion Directly 472 Divergent Plate Boundaries 472 Transform Boundaries 475 Convergent Plate Boundaries 476 Ocean-Ocean Convergence 477 Ocean-Continent Convergence 478 Continent-Continent Convergence 480 Backarc Spreading 481 The Motion of Plate Boundaries 482 Plate Size 482 The Attractiveness of Plate Tectonics 482 What Causes Plate Motions? 483 Mantle Plumes and Hot Spots 486 The Relationship Between Plate Tectonics and Ore Deposits 488 A Final Note 492 Summary 492 Chapter 20 Mountain Belts and the Continental Crust 496 Characteristics of Major Mountain Belts 499 Size and Alignment 499 Ages of Mountain Belts and Continents 499 Thickness and Characteristics of Rock Layers 501 Patterns of Folding and Faulting 502 Metamorphism and Plutonism 504 Normal Faulting 504 Thickness and Density of Rocks 504 Features of Active Mountain Ranges 505 The Evolution of a Mountain Belt 505 The Accumulation Stage 505 The Orogenic Stage 506 The Uplift and Block-faulting Stage 509 The Growth of Continents 514 Suspect and Exotic Terranes 515 Summary 518 Chapter 21 Geologic Resources 520 Types of Resources 522 Resources and Reserves 523 Energy Use 523 Oil and Natural Gas 523 The Occurrence of Oil and Gas 524 Recovering the Oil 526 How Much Oil Do We Have Left? 527 Heavy Crude and Oil Sands 528 Oil Shale 528 Coal 529 Varieties of Coal 529 Occurrence of Coal 530 Environmental Effects 532 Reserves and Resources 532 Uranium 532 Alternative Sources of Energy 533 Metals and Ores 533 Origin of Metallic Ore Deposits 533 Ores Associated with Igneous Rocks 534 Ores Formed by Surface Processes 535 Metal Ores and Plate Tectonics 536 Mining 536 Environmental Effects 537 Some Important Metals 538 Iron 538 Copper 538 Aluminum 538 Lead 539 Zinc 539 Silver 539 Gold 539 Other Metals 540 Nonmetallic Resources 540 Construction Materials 540 Fertilizers and Evaporites 541 Other Nonmetallics 542 Some Future Trends 542 Summary 543 Appendixes A-G 546 Glossary 556 Index 569