Introducing Geology, the Essentials of Plate Tectonics, and Other Important Concepts 3

Transcription

1 Page iv 1 Introducing Geology, the Essentials of Plate Tectonics, and Other Important Concepts 3 2 Atoms, Elements, and Minerals 3 Igneous Rocks, Intrusive Activity, and the Origin of Igneous Rocks 4 Volcanism and Extrusive Rocks 5 Weathering and Soil 6 Sediment and Sedimentary Rocks 7 Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks 8 Time and Geology 9 Mass Wasting Streams and Floods 11 Ground Water 12 Glaciers and Glaciation 13 Deserts and Wind Action 14 Waves, Beaches, and Coasts 15 Geologic Structures 16 Earthquakes 17 Earth s Interior and Geophysical Properties 18 The Sea Floor 19 Plate Tectonics 20 Mountain Belts and the Continental Crust 21 Geologic Resources 22 The Earth s Companions iv

2 Page v Preface xii The Silicon-Oxygen Tetrahedron 36 Nonsilicate Minerals 40 Variations in Mineral Structures and Compositions 40 The Physical Properties of Minerals 41 1 Introducing Geology, the Essentials of Plate Tectonics, and Other Important Concepts 3 Color 41 Streak 42 Luster 42 Hardness 42 External Crystal Form 44 Cleavage 46 Fracture 48 Specific Gravity 48 Special Properties 48 Chemical Tests 49 The Many Conditions of Mineral Formation 49 SUMMARY 51 Who Needs Geology? 4 Supplying Things We Need 4 Protecting the Environment 5 Avoiding Geologic Hazards 5 Understanding Our Surroundings 10 Earth Systems 11 An Overview of Physical Geology Important Concepts 11 Internal Processes: How the Earth s Internal Heat Engine Works 13 Earth s Interior 13 The Theory of Plate Tectonics 14 Divergent Boundaries 14 Convergent Boundaries 15 Transform Boundaries 19 Surficial Processes: The Earth s External Heat Engine 21 The Rock Cycle 56 Geologic Time 24 3 Igneous Rocks, Intrusive Activity, and the Origin of Igneous Rocks 55 A Plate Tectonic Example 57 SUMMARY 25 Igneous Rocks 58 Igneous Rock Textures 59 Identification of Igneous Rocks 59 Varieties of Granite 62 Chemistry of Igneous Rocks 62 Intrusive Bodies 65 Shallow Intrusive Structures 65 Intrusives that Crystallize at Depth 66 2 Abundance and Distribution of Plutonic Rocks 67 How Magma Forms 68 Atoms, Elements, and Minerals 29 Minerals 30 Introduction 30 Atoms and Elements 32 Bonding 34 Ions and Crystalline Structures 35 Heat for Melting Rock 69 Factors that Control Melting Temperatures 69 How Magmas of Different Compositions Evolve 70 Sequence of Crystallization and Melting 70 Differentiation 72 Partial Melting 72 Assimilation 73 Mixing of Magmas 73 v

3 vi Page vi Explaining Igneous Activity by Plate Tectonics 73 Igneous Processes at Divergent Boundaries 73 Intraplate Igneous Activity 75 Igneous Processes at Convergent Boundaries 76 SUMMARY 79 Effects of Weathering 116 Mechanical Weathering 116 Pressure Release 117 Frost Action 117 Other Processes 118 Chemical Weathering 118 Role of Oxygen 119 Role of Acids 120 Solution Weathering 121 Chemical Weathering of Feldspar 122 Chemical Weathering of Other Minerals 123 Weathering Products 123 Factors Affecting Weathering 124 Soil Volcanism and Extrusive Rocks 83 Pyroclastic Debris and Lava Flows 84 Living with Volcanoes 84 Soil Horizons 125 Factors Affecting Soil Formation 127 Soil Erosion 128 Soil Classification 130 SUMMARY 133 Supernatural Beliefs 84 The Growth of an Island 87 Geothermal Energy 87 Effect on Climate 87 Volcanic Catastrophes 87 Eruptive Violence and Physical Characteristics of Lava 90 Extrusive Rocks and Gases 91 Scientific Investigation of Volcanism 91 Gases 91 Extrusive Rocks 92 6 Sediment and Sedimentary Rocks 137 Composition 92 Extrusive Textures 93 Sediment 139 Types of Volcanoes 95 Transportation 139 Deposition 140 Preservation 141 Lithification 141 Shield Volcanoes 98 Cinder Cones 99 Composite Volcanoes 100 Volcanic Domes 103 Types of Sedimentary Rocks 143 Detrital Rocks 143 Lava Floods 104 Submarine Eruptions 108 Breccia and Conglomerate 143 Sandstone 145 The Fine-Grained Rocks 146 Pillow Basalts 108 SUMMARY 109 Chemical Sedimentary Rocks 147 Carbonate Rocks 147 Chert 151 Evaporites 151 Organic Sedimentary Rocks 152 Coal Weathering and Soil 113 Weathering, Erosion, and Transportation 114 Weathering and Earth Systems 114 Atmosphere 114 Hydrosphere 114 Biosphere 115 The Origin of Oil and Gas 152 Sedimentary Structures 153 Fossils 157 Formations 158 Interpretation of Sedimentary Rocks 159 Source Area 159 Environment of Deposition 160 Transgression and Regression 163 Plate Tectonics and Sedimentary Rocks 163 SUMMARY 165 How Weathering Changes Rocks 115

4 Page vii Combining Relative and Numerical Ages 212 Age of the Earth 213 Comprehending Geologic Time 214 SUMMARY Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks 169 Introduction 170 Factors Controlling the Characteristics of Metamorphic Rocks 171 Composition of the Parent Rock 172 Temperature 172 Pressure 173 Fluids 174 Time 175 Classification of Metamorphic Rocks 175 Nonfoliated Rocks 175 Foliated Rocks 177 Types of Metamorphism Mass Wasting 221 Introduction to Mass Wasting 222 Classification of Mass Wasting 223 Rate of Movement 223 Type of Material 223 Type of Movement 223 Controlling Factors in Mass Wasting 226 Contact Metamorphism 179 Regional Metamorphism 179 Plate Tectonics and Metamorphism 183 Foliation and Plate Tectonics 183 Pressure-Temperature Regimes 183 Gravity 226 Water 227 Triggering Mechanisms 228 Common Types of Mass Wasting 228 Hydrothermal Processes 185 Hydrothermal Activity at Divergent Plate Boundaries 186 Water at Convergent Boundaries 187 Metasomatism 187 Hydrothermal Rocks and Minerals 188 SUMMARY 190 Creep 228 Flow 230 Rockfalls and Rockslides 234 Underwater Landslides 237 Preventing Landslides 238 Preventing Mass Wasting of Soil 238 Preventing Rockfalls and Rockslides on Highways 242 SUMMARY Time and Geology 193 The Key to the Past 194 Relative Time 195 Principles Used to Determine Relative Age 195 Unconformities 200 Correlation 202 The Standard Geologic Time Scale 205 Numerical Age 205 Isotopic Dating 206 Uses of Isotopic Dating Streams and Floods 247 Earth Systems The Hydrologic Cycle 248 Running Water 249 Drainage Basins 250 Drainage Patterns 250 Factors Affecting Stream Erosion and Deposition 251 Velocity 251 Gradient 253 Channel Shape and Roughness 253 Discharge 253 vii

5 viii Page viii Stream Erosion 254 Stream Transportation of Sediment 255 Stream Deposition 257 Bars 257 Braided Streams 260 Meandering Streams and Point Bars 260 Flood Plains 261 Deltas 263 Alluvial Fans 267 Flooding 267 Urban Flooding 270 Flash Floods 270 Controlling Floods 270 The Great Flood of Glaciers and Glaciation 307 Introduction 308 Glaciers Where They Are, How They Form and Move 309 Stream Valley Development 272 Downcutting and Base Level 272 The Concept of a Graded Stream 275 Lateral Erosion 275 Headward Erosion 275 Distribution of Glaciers 309 Types of Glaciers 309 Formation and Growth of Glaciers 309 Movement of Valley Glaciers 312 Movement of Ice Sheets 314 Glacial Erosion 316 Erosional Landscapes Associated with Alpine Glaciation 317 Erosional Landscapes Associated with Continental Glaciation 321 Stream Terraces 276 Incised Meanders 276 SUMMARY 280 Glacial Deposition 322 Moraines 323 Outwash 326 Glacial Lakes and Varves 327 Past Glaciation 327 Direct Effects of Past Glaciation in North America 330 Indirect Effects of Past Glaciation 331 Evidence for Older Glaciation 334 SUMMARY Ground Water 283 Introduction 284 Porosity and Permeability 284 The Water Table 285 The Movement of Ground Water 286 Aquifers 288 Wells 289 Springs and Streams 290 Contamination of Ground Water 292 Balancing Withdrawal and Recharge 296 Effects of Groundwater Action 297 Caves, Sinkholes, and Karst Topography 297 Other Effects 300 Hot Water Underground 300 Geothermal Energy 301 SUMMARY Deserts and Wind Action 339 Distribution of Deserts 340 Some Characteristics of Deserts 341 Desert Features in the Southwestern United States 344 Wind Action 349 Wind Erosion and Transportation 349 Wind Deposition 351 SUMMARY 358

6 Page ix Waves, Beaches, and Coasts 361 Introduction 362 Water Waves 362 Surf 363 Wave Refraction 364 Longshore Currents 364 Rip Currents 364 Locating and Measuring Earthquakes 413 Determining the Location of an Earthquake 413 Measuring the Size of an Earthquake 416 Location and Size of Earthquakes in the United States 419 Beaches 366 Longshore Drift of Sediment 367 Human Interference with Sand Drift 368 Sources of Sand on Beaches 370 Coasts and Coastal Features 370 Tsunami 425 Earthquakes at Plate Boundaries 430 Subduction Angle 433 Earthquake Prediction and Seismic Risk 433 SUMMARY 380 SUMMARY Geologic Structures 383 Tectonic Forces at Work 384 Stress and Strain in the Earth s Lithosphere 384 How Do Rocks Behave When Stressed? 385 Structures as a Record of the Geologic Past 386 Geologic Maps and Field Methods 386 Folds 388 Geometry of Folds 389 Further Description of Folds 391 SUMMARY 403 Effects of Earthquakes 421 World Distribution of Earthquakes 428 First-Motion Studies of Earthquakes 428 Earthquakes and Plate Tectonics 428 Erosional Coasts 370 Depositional Coasts 372 Drowned Coasts 373 Uplifted Coasts 374 The Biosphere and Coasts 375 Joints 393 Faults 395 Introduction 408 Causes of Earthquakes 410 Seismic Waves 411 Body Waves 412 Surface Waves 413 Near-Shore Circulation 364 Fractures in Rock 393 Earthquakes Earth s Interior and Geophysical Properties 443 Introduction 444 Evidence from Seismic Waves 444 Earth s Internal Structure 446 The Crust 446 The Mantle 447 The Core 449 Isostasy 452 Gravity Measurements 454 Earth s Magnetic Field 455 Magnetic Reversals 457 Magnetic Anomalies 458 ix

7 x 4:04 PM Page x Heat within the Earth 460 Paleomagnetism and the Revival of Continental Drift 496 Geothermal Gradient 460 Heat Flow 461 Recent Evidence for Continental Drift 497 History of Continental Positions 498 Seafloor Spreading 498 SUMMARY 463 Hess s Driving Force 498 Explanations 499 Plates and Plate Motion 500 How Do We Know that Plates Move? 500 Marine Magnetic Anomalies 500 Another Test: Fracture Zones and Transform Faults 503 Measuring Plate Motion Directly The Sea Floor 467 Origin of the Ocean 468 Methods of Studying the Sea Floor 468 Features of the Sea Floor 470 Continental Shelves and Continental Slopes 470 Submarine Canyons 472 Turbidity Currents 473 Passive Continental Margins 474 The Continental Rise 475 Abyssal Plains 475 Divergent Plate Boundaries 504 Transform Boundaries 509 Convergent Plate Boundaries 509 Ocean-Ocean Convergence 509 Ocean-Continent Convergence 511 Continent-Continent Convergence 511 The Motion of Plate Boundaries 512 Plate Size 515 The Attractiveness of Plate Tectonics 515 What Causes Plate Motions? 516 Mantle Convection 516 Ridge Push 517 Slab Pull 517 Trench Suction 517 Mantle Plumes and Hot Spots 517 A Final Note 518 Active Continental Margins 476 Oceanic Trenches 476 SUMMARY 522 Mid-Oceanic Ridges 477 Geologic Activity at the Ridges 477 Biologic Activity at the Ridges 479 Fracture Zones 479 Seamounts, Guyots, and Aseismic Ridges 479 Reefs 481 Sediments of the Sea Floor 483 Oceanic Crust and Ophiolites 483 The Age of the Sea Floor 486 The Sea Floor and Plate Tectonics 486 SUMMARY Mountain Belts and the Continental Crust 527 Introduction 528 Characteristics of Major Mountain Belts Plate Tectonics 491 The Early Case for Continental Drift 493 Skepticism about Continental Drift 495 Size and Alignment 531 Ages of Mountain Belts and Continents 531 Thickness and Characteristics of Rock Layers 532 Patterns of Folding and Faulting 533 Metamorphism and Plutonism 533 Normal Faulting 534 Thickness and Density of Rocks 535 Features of Active Mountain Ranges 536 Evolution of Mountain Belts 536 Orogenies and Plate Convergence 536 Post-Orogenic Uplift and Block-Faulting 541 The Growth of Continents 545 Displaced Terranes 545 SUMMARY 548

8 4:04 PM Page xi xi 21 Geologic Resources 551 The Introduction 552 Energy Resources 552 Coal 553 Petroleum and Natural Gas 556 Coal Bed Methane 562 Heavy Crude and Oil Sands 562 Oil Shale 564 Uranium 565 Geothermal Power 566 Renewable Energy Sources 568 Metallic Resources 569 Ores Formed by Igneous Processes 569 Ores Formed by Surface Processes 571 Mining 572 Some Important Metals 573 Nonmetallic Resources 576 Construction Materials 576 Fertilizers and Evaporites 577 Other Nonmetallics 577 The Human Perspective 578 SUMMARY Earth s Companions 583 The Earth in Space 584 The Sun 584 The Solar System 585 The Milky Way and the Universe 586 Origin of the Planets 588 The Solar Nebula 588 Formation of the Planets 590 Formation of Moons 590 Final Stages of Planet Formation 590 Formation of Atmospheres 590 Other Planetary Systems 590 Portraits of the Planets 591 Our Moon 591 Mercury 597 Venus 598 Mars 600 Why Are the Terrestrial Planets So Different? 606 Jupiter 607 Saturn 608 Uranus 610 Neptune 610 Pluto and the Ice Dwarfs 610 Minor Objects of the Solar System 612 Meteors and Meteorites 612 Meteorites 612 Asteroids 613 Comets 613 Giant Impacts 615 Giant Meteor Impacts 615 SUMMARY 616 Appendices A G 618 Glossary 630 Index 642