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Contents iv Preface xii Meet the Authors xix Introducing Geology and an Overview of Important Concepts 3 Who Needs Geology? 4 Supplying Things We Need 4 Protecting the Environment 5 Avoiding Geologic Hazards 5 Understanding Our Surroundings 8 Earth Systems 9 An Overview of Physical Geology-Important Concepts 10 Internal Processes: How the Earth's Internal Heat Engine Works 12 Earth's Interior 12 The Theory of Plate Tectonics 13 Surficial Processes: The Earth's External Heat Engine 16 Geologic Time 17 SUMMARY 21 Atoms, Elements, and Minerals 25 Introduction 26 Atoms and Elements 27 Chemical Activity 30 Ions 30 Chemical Composition of the Earth's Crust 30 Crystallinity 32 The Silicon-Oxygen Tetrahedron 33 Nonsilicate Minerals 35 Minerals 35 Crystalline Solid 37 Geologic Processes 37 Specific Chemical Composition 37 The Important Minerals 37 The Physical Properties of Minerals 40 Color 40 Streak 40 Luster 40 Hardness 40 External Crystal Form 41 Cleavage 43 Fracture 44 Specific Gravity 45 Special Properties 46 Other Properties 46 Chemical Tests 47 SUMMARY 47 Igneous Rocks, Intrusive Activity, and the Origin of Igneous Rocks 51 The Rock Cycle 52 A Plate-Tectonic Example 53 Igneous Rocks 53 Igneous Rock Textures 55 Identification of Igneous Rocks 57 Varieties of Granite 58 Chemistry of Igneous Rocks 58 Intrusive Bodies 60 Shallow Intrusive Structures 60 Intrusives That Crystallize at Depth 61 Abundance and Distribution of Plutonic Rocks 63 How Magma Forms 64 Heat for Melting Rock 64 Factors That Control Melting Temperatures 64 How Magmas of Different Compositions Evolve 66 Sequence of Crystallization and Melting 66 Differentiation 67 Partial Melting 68 Assimilation 68 Mixing of Magmas 69 Explaining Igneous Activity by Plate Tectonics 69 Igneous Processes at Divergent Boundaries 69 Intraplate Igneous Activity 69 Igneous Processes at Convergent Boundaries 70 SUMMARY 73 Volcanism and Extrusive Rocks 77 Introduction 78 Living with Volcanoes 81 Supernatural Beliefs 81 The Growth of an Island 81 Geothermal Energy 81 Effect on Climate 81 Volcanic Catastrophes 81 Eruptive Violence and Physical Characteristics of Lava 84 Extrusive Rocks and Gases 85 Scientific Investigation of Volcanism 85 Gases 85 Extrusive Rocks 86 Composition 86 Extrusive Textures 87 Types of Volcanoes 89 Shield Volcanoes 90 Cinder Cones 92 Composite Volcanoes 94 Volcanic Domes 96 Lava Floods 99 Submarine Eruptions 100 Pillow Basalts 100 SUMMARY 102 Weathering and Soil 107 Weathering, Erosion, and Transportation 108 Weathering and Earth Systems 108 Solar System 108 Atmosphere 109 Hydrosphere 109 Biosphere 109 How Weathering Alters Rock 109 Effects of Weathering 109 Mechanical Weathering 111 Frost Action 111 Pressure Release 111 Other Processes 111 Chemical Weathering 113 Role of Oxygen 114 Role of Acids 114 Solution Weathering 114 Chemical Weathering of Feldspar 116 Chemical Weathering of Other Minerals 116 Weathering Products 118 Weathering and Climate 118 Soil 118 Soil Horizons 119 Soil Classification 119 Residual and Transported Soils 120 Soils, Parent Material, Time, and Slope 120 Organic Activity 122 Soils and Climate 122 Buried Soils 124 SUMMARY 124 Sediment and Sedimentary Rocks 127 Sediment 129 Transportation 129 Deposition 130 Preservation 131 Lithification 132 Types of Sedimentary Rocks 133 Clastic Rocks 133 Breccia and Conglomerate 133 Sandstone 135 The Fine-Grained Rocks 136 Chemical Sedimentary Rocks 137 Carbonate Rocks 137 Chert 141 Evaporites 141 Organic Sedimentary Rocks 142 Coal 142 The Origin of Oil and Gas 142 Sedimentary Structures 142 Formations 147 Interpretation of Sedimentary Rocks 148 Source Area 148 Environment of Deposition 150 Plate Tectonics and Sedimentary Rocks 152 SUMMARY 153 Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks 157 Introduction 158 Factors Controlling the Characteristics of Metamorphic Rocks 159 Composition of the Parent Rock 160 Temperature 160 Pressure 160 Fluids 162 Time 162 Classification of Metamorphic Rocks 163 Types of Metamorphism 163 Contact Metamorphism 163 Regional Metamorphism 165 Plate Tectonics and Metamorphism 169 Hydrothermal Processes 172 Hydrothermal Activity at Divergent Plate Boundaries 172 Water at Convergent Boundaries 173 Metasomatism 173 Hydrothermal Rocks and Minerals 174 SUMMARY 176 Time and Geology 179 The Key to the Past 180 Relative Time 181 Principles Used to Determine Relative Age 181 Unconformities 186 Correlation 187 The Standard Geologic Time Scale 191 Numerical Age 193 Isotopic Dating 193 Uses of Isotopic Dating 196 Combining Relative and Numerical Ages 198 Age of the Earth 199 Comprehending Geologic Time 201 SUMMARY 201 Mass Wasting 205 Classification of Mass Wasting 206 Rate of Movement 206 Type of Material 206 Type of Movement 206 Controlling Factors in Mass Wasting 208 Gravity 210 Water 210 Triggering Mechanisms 211 Common Types of Mass Wasting 212 Creep 212 Debris Flow 213 Rockfalls and Rockslides 217 Underwater Slides 220 Preventing Landslides 221 Preventing Mass Wasting of Debris 221 Preventing Rockfalls and Rockslides on Highways 222 SUMMARY 224 Streams and Floods 227 Earth Systems-The Hydrologic Cycle 229 Channel Flow and Sheet Flow 229 Drainage Basins 230 Drainage Patterns 231 Factors Affecting Stream Erosion and Deposition 231 Velocity 232 Gradient 233 Channel Shape and Roughness 233 Discharge 234 Stream Erosion 235 Stream Transportation of Sediment 236 Stream Deposition 237 Bars 237 Braided Streams 240 Meandering Streams and Point Bars 241 Flood Plains 243 Deltas 243 Alluvial Fans 246 Kaibab Limestone Toroweap Formation Coconino Sandstone Hermit Shale Supai Formation Redwall Limestone Hermit Shale Supai Formation Redwall Limestone Flooding 246 Urban Flooding 247 Flash Floods 247 Controlling Floods 251 The Great Flood of 1993 251 Stream Valley Development 253 Downcutting and Base Level 253 The Concept of a Graded Stream 253 Lateral Erosion 255 Headward Erosion 255 Stream Terraces 256 Incised Meanders 257 Superposed Streams 257 SUMMARY 259 Ground Water 263 Introduction 264 Porosity and Permeability 264 The Water Table 265 The Movement of Ground Water 267 Aquifers 268 Wells 269 Springs and Streams 270 Contamination of Ground Water 272 Balancing Withdrawal and Recharge 277 Effects of Ground-Water Action 277 Caves, Sinkholes, and Karst Topography 277 Other Effects 280 Hot Water Underground 281 Geothermal Energy 282 SUMMARY 283 Glaciers and Glaciation 287 The Theory of Glacial Ages 288 Glaciers-What They Are, How They Form and Move 289 Distribution of Glaciers 289 Types of Glaciers 289 Formation and Growth of Glaciers 291 Movement of Valley Glaciers 292 Movement of Ice Sheets 296 Glacial Erosion 298 Erosional Landscapes Associated with Alpine Glaciation 298 Erosional Landscapes Associated with Continental Glaciation 301 Glacial Deposition 302 Moraines 303 Outwash 305 Glacial Lakes and Varves 306 Effects of Past Glaciation 308 The Glacial Ages 308 Direct Effects of Past Glaciation in North America 309 Indirect Effects of Past Glaciation 310 Evidence for Older Glaciation 311 SUMMARY 313 Deserts and Wind Action 317 Distribution of Deserts 318 Some Characteristics of Deserts 319 Desert Features in the Southwestern United States 322 Wind Action 326 Wind Erosion and Transportation 326 Wind Deposition 328 SUMMARY 330 Waves, Beaches, and Coasts 339 Introduction 340 Water Waves 340 Surf 341 Near-shore Circulation 342 Wave Refraction 342 Longshore Currents 342 Rip Currents 342 Beaches 344 Longshore Drift of Sediment 345 Human Interference with Sand Drift 346 Sources of Sand on Beaches 348 Coasts and Coastal Features 348 Erosional Coasts 349 Depositional Coasts 350 Drowned Coasts 351 Uplifted Coasts 352 The Biosphere and Coasts 353 SUMMARY 356 Geologic Structures 359 Introduction 360 Tectonic Forces at Work 360 Stress and Strain in the Earth's Crust 360 Behavior of Rocks to Stress and Strain 361 Present Deformation of the Crust 362 Structures as a Record of the Geologic Past 362 Geologic Maps and Field Methods 362 Folds 365 Geometry of Folds 365 Interpreting Folds 368 Fractures in Rock 369 Joints 369 Faults 370 SUMMARY 379 Earthquakes 383 Introduction 384 Causes of Earthquakes 386 Seismic Waves 387 Body Waves 388 Surface Waves 389 Locating and Measuring Earthquakes 389 Determining the Location of an Earthquake 389 Measuring the Size of an Earthquake 392 Location and Size of Earthquakes in the United States 395 Effects of Earthquakes 395 Tsunami 399 World Distribution of Earthquakes 403 First-Motion Studies of Earthquakes 403 Earthquakes and Plate Tectonics 405 Earthquakes at Plate Boundaries 405 Subduction Angle 407 Earthquake Prediction and Seismic Risk 407 SUMMARY 412 Earth's Interior and Geophysical Properties 417 Introduction 418 Evidence from Seismic Waves 418 Earth's Internal Structure 421 The Crust 421 The Mantle 422 The Core 424 Isostasy 428 Gravity Measurements 429 Earth's Magnetic Field 432 Magnetic Reversals 433 Magnetic Anomalies 434 Heat Within the Earth 437 Geothermal Gradient 437 Heat Flow 438 SUMMARY 439 The Sea Floor 443 Origin of the Ocean 444 Methods of Studying the Ocean Floor 444 Features of the Sea Floor 446 Continental Shelves and Continental Slopes 446 Submarine Canyons 448 Turbidity Currents 449 Passive Continental Margins 450 The Continental Rise 451 Abyssal Plains 451 Active Continental Margins 452 Oceanic Trenches 452 The Mid-Oceanic Ridge 453 Geologic Activity on the Ridge 453 Biologic Activity on the Ridge 455 Fracture Zones 455 Seamounts, Guyots, and Aseismic Ridges 456 Reefs 457 Sediments of the Sea Floor 459 Oceanic Crust and Ophiolites 459 The Age of the Sea Floor 462 The Sea Floor and Plate Tectonics 462 SUMMARY 462 Plate Tectonics 467 The Early Case for Continental Drift 469 Skepticism About Continental Drift 472 Paleomagnetism and the Revival of Continental Drift 472 Recent Evidence for Continental Drift 473 History of Continental Positions 474 Seafloor Spreading 474 Hess's Driving Force 474 Explanations 475 Plates and Plate Motion 476 How Do We Know That Plates Move? 477 Marine Magnetic Anomalies 477 Another Test: Fracture Zones and Transform Faults 480 Measuring Plate Motion Directly 480 Divergent Plate Boundaries 481 Transform Boundaries 484 Convergent Plate Boundaries 485 Ocean-Ocean Convergence 486 Ocean-Continent Convergence 487 Continent-Continent Convergence 489 Backarc Spreading 490 The Motion of Plate Boundaries 490 Plate Size 491 The Attractiveness of Plate Tectonics 491 What Causes Plate Motions? 492 Mantle Plumes and Hot Spots 494 The Relationship Between Plate Tectonics and Ore Deposits 497 A Final Note 498 SUMMARY 499 Mountain Belts and the Continental Crust 503 Characteristics of Major Mountain Belts 506 Size and Alignment 506 Ages of Mountain Belts and Continents 506 Thickness and Characteristics of Rock Layers 508 Patterns of Folding and Faulting 508 Metamorphism and Plutonism 510 Normal Faulting 510 Thickness and Density of Rocks 510 Features of Active Mountain Ranges 511 The Evolution of a Mountain Belt 511 The Accumulation Stage 511 The Orogenic Stage 512 The Uplift and Block-Faulting Stage 515 The Growth of Continents 520 Displaced Terranes 520 SUMMARY 522 Geologic Resources 525 Types of Resources 526 Resources and Reserves 527 Energy Use 527 Oil and Natural Gas 528 The Occurrence of Oil and Gas 528 Recovering the Oil 529 How Much Petroleum Do We Have Left? 530 Heavy Crude and Oil Sands 530 Oil Shale 532 Coal 532 Varieties of Coal 532 Occurrence of Coal 533 Environmental Effects 535 Reserves and Resources 535 Uranium 535 Alternative Sources of Energy 536 Metals and Ores 536 Origin of Metallic Ore Deposits 536 Ores Associated with Igneous Rocks 537 Ores Formed by Surface Processes 538 Mining 539 Environmental Effects 539 Some Important Minerals 540 Iron 540 Copper 541 Aluminum 541 Lead 541 Zinc 542 Silver 542 Gold 542 Other Metals 543 Nonmetallic Resources 543 Construction Materials 543 Fertilizers and Evaporites 544 Other Nonmetallics 544 Some Future Trends 544 The Human Perspective 544 SUMMARY 545 The Earth's Companions 549 The Earth in Space 550 The Sun 550 The Solar System 550 The Milky Way and the Universe 554 Origin of the Planets 554 The Solar Nebula 554 Formation of the Planets 556 Formation of Moons 557 Final Stages of Planet Formation 557 Formation of Atmospheres 557 Other Planetary Systems 557 Portraits of the Planets 558 Our Moon 558 Description of the Moon 559 Structure of the Moon 562 Origin and History of the Moon 562 Mercury 564 Venus 565 Mars 566 Why Are the Terrestrial Planets So Different? 570 Jupiter 571 Saturn 573 Uranus 574 Neptune 574 Pluto 575 Minor Objects of the Solar System 575 Meteors and Meteorites 575 Asteroids 576 Comets 576 Giant Impacts 578 Giant Meteor Impacts 578 SUMMARY 579 Appendixes A-G A-1 Glossary G-1 Index I-1
Library of Congress Subject Headings for this publication:
Physical geology -- Textbooks.