Confi rming Pages Generalized Geologic and Tectonic Map of North America SEDIMENTARY UNITS SPECIAL UNITS PRECAMBRIAN Thick deposits in structurally Paleozoic and Mesozoic Former subduction complex Exposed parts of Basement igneous and negative areas active margin deposits rocks of the Pacific border Ouachita foldbelt metamorphic complexes mainly of Precambrian age Synorogenic and Paleozoic and Mesozoic postorogenic deposits passive margin deposits Proboaf bIlnen wuietisatenr nfo eldxbteenltsion Grenville foldbelt In cores of northern Deformed 880–1,000 m.y. ago Alaska ranges Late Precambrian deposits PLATFORM AREAS Of Middle and Upper Proterozoic ages Hudsonian foldbelts Deformed 1,640–1,820 m.y. ago VOLCANIC AND PLUTONIC UNITS Ice cap of Quaternary age Platform deposits on On Precambrian and Precambrian basement Paleozoic basement In central craton Kenoran foldbelts Postorogenic volcanic cover Ultramafic rocks Deformed 2,390–2,600 m.y. ago Platform deposits on Platform deposits within Paleozoic basement the Precambrian Granitic plutons In Atlantic and Mainly in the Anorthosite bodies Ages are generally within the Gulf coastal plains Canadian Shield Plutons composed almost span of the tectonic cycle of entirely of plagioclase the foldbelt in which they lie STRUCTURAL SYMBOLS Normal fault Subsea fault Hachures on downthrown side Salt domes and salt diapirs In Gulf coastal plain Strike-slip fault and Gulf of Mexico Arrows show relative lateral movement Volcano Thrust fault World’s oldest rock Barbs on upthrown side 1000 0 +1000 Contours on basement surfaces beneath platform areas Axes of seafloor spreading All contours are below sea level except where marked with plus symbols. Interval is 1,000 meters Modified from the Generalized Tectonic Map of North America by P.B. King and Gertrude J. Edmonston, U.S. Geological Survey Map I-688 Metamorphic Shale Conglomerate Granite basement rock Basalt Limestone Sandstone Breccia Crystalline Cross-bedded continental Dolomite sandstone Rock salt crust ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd ii 11//1188//1100 1100::5500::1155 PPMM This page intentionally left blank Confi rming Pages Ninth Edition Diane H. Carlson California State University at Sacramento Charles C. Plummer Emeritus of California State University at Sacramento Lisa Hammersley California State University at Sacramento ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd iiiiii 11//1188//1100 1100::5500::1155 PPMM Confi rming Pages TM PHYSICAL GEOLOGY: EARTH REVEALED, NINTH EDITION Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue of the Americas, New York, NY 10020. Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved. Previous editions © 2009, 2008, and 2006. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of The McGraw-Hill Companies, Inc., including, but not limited to, in any network or other electronic storage or transmission, tor broadcast for distance learning. Some ancillaries, including electronic and print components, may not be available to customers outside the United States. This book is printed on acid-free paper. 1 2 3 4 5 6 7 8 9 0 DOW/DOW 1 0 9 8 7 6 5 4 3 2 1 0 ISBN 978-0-07-336940-2 MHID 0-07-336940-3 Vice President & Editor-in-Chief: Martin Lange VP EDP / Central Publishing Services: Kimberly Meriwether David Publisher: Ryan Blankenship Executive Editor: Margaret J. Kemp Senior Marketing Manager: Lisa Nicks Project Manager: Robin A. Reed Design Coordinator: Brenda A. Rolwes Cover Designer: Studio Montage, St. Louis, Missouri Lead Photo Research Coordinator: Carrie K. Burger USE Cover Image Credit: © Digital Vision/Getty Images Senior Production Supervisor: Laura Fuller Senior Media Project Manager: Tammy Juran Composition: Laserwords Private Limited Typeface: 10.5/12 Times Roman Printer: R. R. Donnelley All credits appearing on page or at the end of the book are considered to be an extension of the copyright page. Library of Congress Cataloging-in-Publication Data Carlson, Diane H. Physical geology: earth revealed.—9th ed. / Diane H. Carlson, Charles C. Plummer, Lisa Hammersley. p. cm. McGeary’s name appears first on the earlier eds. Companion text to Earth revealed, a PBS television course and video resource. Includes bibliographical references and index. ISBN-13: 978-0-07-336940-2 (softcover : alk. paper) ISBN-10: 0-07-336940-3 (softcover : alk. paper) I. Plummer, Charles C., 1937- II. Hammersley, Lisa. III. Plummer, Charles C., 1937- IV. Hammersley, Lisa. V. Earth revealed (Television program) VI. Title. VII. Title: Earth revealed. QE28.2.M34 2010 550—dc22 2009040823 The Internet addresses listed in the text were accurate at the time of publication. The inclusion of a Web site does not indicate an endorsement by the authors or McGraw-Hill, and McGraw-Hill does not guarantee the accuracy of the information presented at these sites. www.mhhe.com ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd iivv 11//1188//1100 1100::5500::2277 PPMM Confi rming Pages Chapter 1 Introducing Geology, the Essentials of Plate Tectonics, and Other Important Concepts 3 Chapter 2 Earth’s Interior and Geophysical Properties 29 Chapter 3 The Sea Floor 53 Chapter 4 Plate Tectonics 75 Chapter 5 Mountain Belts and the Continental Crust 111 Chapter 6 Geologic Structures 135 Chapter 7 Earthquakes 157 Chapter 8 Time and Geology 189 Chapter 9 Atoms, Elements, and Minerals 217 Chapter 10 Volcanism and Extrusive Rocks 243 Chapter 11 Igneous Rocks, Intrusive Activity, and the Origin of Igneous Rocks 275 Chapter 12 Weathering and Soil 301 Chapter 13 Mass Wasting 325 Chapter 14 Sediment and Sedimentary Rocks 351 Chapter 15 Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks 383 Chapter 16 Streams and Floods 407 Chapter 17 Ground Water 443 Chapter 18 Deserts and Wind Action 467 Chapter 19 Glaciers and Glaciation 489 Chapter 20 Waves, Beaches, and Coasts 521 Chapter 21 Resources 543 Chapter 22 The Earth’s Companions 573 v ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd vv 11//1188//1100 1100::5500::2277 PPMM Confi rming Pages Preface xiii Earth’s Internal Structure 32 The Crust 32 The Mantle 33 The Core 35 Isostasy 38 Gravity Measurements 40 Earth’s Magnetic Field 41 Magnetic Reversals 43 Magnetic Anomalies 44 1 Heat within the Earth 46 Geothermal Gradient 46 Introducing Geology, the Essentials Heat Flow 47 of Plate Tectonics, and Other SUMMARY 49 Important Concepts 3 Who Needs Geology? 4 Supplying Things We Need 4 Protecting the Environment 5 Avoiding Geologic Hazards 5 Understanding Our Surroundings 11 Earth Systems 11 An Overview of Physical Geology—Important Concepts 13 3 Internal Processes: How the Earth’s Internal Heat Engine Works 13 The Sea Floor 53 Earth’s Interior 14 The Theory of Plate Tectonics 15 Origin of the Ocean 54 Divergent Boundaries 15 Convergent Boundaries 18 Methods of Studying the Sea Floor 54 Transform Boundaries 20 Features of the Sea Floor 56 Surficial Processes: The Earth’s External Heat Engine 20 Continental Shelves and Continental Slopes 56 Geologic Time 25 Submarine Canyons 58 SUMMARY 26 Turbidity Currents 59 Passive Continental Margins 60 The Continental Rise 61 Abyssal Plains 61 Active Continental Margins 62 Oceanic Trenches 62 Mid-Oceanic Ridges 63 Geologic Activity at the Ridges 63 Biologic Activity at the Ridges 64 Fracture Zones 64 Seamounts, Guyots, and Aseismic Ridges 65 2 Reefs 66 Earth’s Interior and Geophysical Sediments of the Sea Floor 68 Properties 29 Oceanic Crust and Ophiolites 68 The Age of the Sea Floor 71 The Sea Floor and Plate Tectonics 71 Introduction 30 Evidence from Seismic Waves 30 SUMMARY 71 vi ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd vvii 11//1188//1100 1100::5500::3300 PPMM Confi rming Pages CONTENTS vii Thickness and Characteristics of Rock Layers 116 Patterns of Folding and Faulting 117 Metamorphism and Plutonism 117 Normal Faulting 118 Thickness and Density of Rocks 119 Features of Active Mountain Ranges 120 Evolution of Mountain Belts 120 Orogenies and Plate Convergence 120 4 Post-Orogenic Uplift and Block-Faulting 126 Plate Tectonics 75 The Growth of Continents 129 Displaced Terranes 130 The Early Case for Continental Drift 77 SUMMARY 131 Skepticism about Continental Drift 79 Paleomagnetism and the Revival of Continental Drift 80 Recent Evidence for Continental Drift 81 History of Continental Positions 82 Seafloor Spreading 82 Hess’s Driving Force 82 Explanations 83 Plates and Plate Motion 84 How Do We Know that Plates Move? 84 6 Marine Magnetic Anomalies 84 Another Test: Fracture Zones and Transform Faults 87 Geologic Structures 135 Measuring Plate Motion Directly 88 Divergent Plate Boundaries 88 Transform Boundaries 93 Tectonic Forces at Work 136 Stress and Strain in the Earth’s Lithosphere 136 Convergent Plate Boundaries 93 How Do Rocks Behave When Stressed? 137 Ocean-Ocean Convergence 93 Structures as a Record of the Geologic Past 138 Ocean-Continent Convergence 95 Continent-Continent Convergence 95 Geologic Maps and Field Methods 138 The Motion of Plate Boundaries 96 Folds 140 Geometry of Folds 141 Plate Size 99 Further Description of Folds 143 The Attractiveness of Plate Tectonics 99 Fractures in Rock 145 What Causes Plate Motions? 100 Joints 145 Mantle Convection 100 Faults 147 Ridge Push 101 SUMMARY 154 Slab Pull 101 Trench Suction 101 Mantle Plumes and Hot Spots 101 A Final Note 102 SUMMARY 106 7 Earthquakes 157 Causes of Earthquakes 158 5 Seismic Waves 159 Mountain Belts and the Continental Body Waves 159 Surface Waves 160 Crust 111 Locating and Measuring Earthquakes 161 Determining the Location of an Earthquake 161 Introduction 112 Measuring the Size of an Earthquake 163 Characteristics of Major Mountain Belts 115 Location and Size of Earthquakes in the United States 165 Size and Alignment 115 Effects of Earthquakes 167 Ages of Mountain Belts and Continents 115 Tsunami 171 ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd vviiii 11//1188//1100 1100::5500::3399 PPMM Confi rming Pages viii CONTENTS World Distribution of Earthquakes 174 Cleavage 234 Fracture 236 First-Motion Studies of Earthquakes 177 Specific Gravity 236 Earthquakes and Plate Tectonics 177 Special Properties 236 Earthquakes at Plate Boundaries 178 Chemical Tests 237 Subduction Angle 179 The Many Conditions of Mineral Formation 239 Earthquake Prediction and Seismic Risk 179 SUMMARY 239 SUMMARY 185 10 8 Volcanism and Extrusive Rocks 243 Time and Geology 189 Relationships to Earth Systems 244 The Key to the Past 190 Pyroclastic Debris and Lava Flows 244 Relative Time 191 Living with Volcanoes 244 Principles Used to Determine Relative Age 191 Unconformities 196 Supernatural Beliefs 244 Correlation 198 The Growth of an Island 247 The Standard Geologic Time Scale 201 Geothermal Energy 247 Numerical Age 201 Effect on Climate 247 Volcanic Catastrophes 247 Isotopic Dating 202 Eruptive Violence and Physical Characteristics of Lava 250 Uses of Isotopic Dating 207 Extrusive Rocks and Gases 252 Combining Relative and Numerical Ages 208 Scientific Investigation of Volcanism 252 Age of the Earth 209 Gases 252 Comprehending Geologic Time 210 Extrusive Rocks 253 SUMMARY 212 Composition 253 Extrusive Textures 254 Types of Volcanoes 257 Shield Volcanoes 258 Cinder Cones 258 Composite Volcanoes 260 Volcanic Domes 263 Lava Floods 263 Submarine Eruptions 268 Pillow Basalts 268 9 SUMMARY 270 Atoms, Elements, and Minerals 217 Relationships to Earth Systems 218 Minerals 218 Introduction 218 Minerals and Rocks 219 Atoms and Elements 220 Ions and Bonding 222 Crystalline Structures 223 The Silicon-Oxygen Tetrahedron 224 11 Nonsilicate Minerals 229 Igneous Rocks, Intrusive Activity, Variations in Mineral Structures and Compositions 229 The Physical Properties of Minerals 229 and the Origin of Igneous Rocks 275 Color 230 Streak 230 Relationships to Earth Systems 276 Luster 231 Hardness 231 The Rock Cycle 276 External Crystal Form 232 A Plate Tectonic Example 277 ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd vviiiiii 11//1188//1100 1100::5511::1100 PPMM Confi rming Pages CONTENTS ix Igneous Rocks 278 Soil Erosion 318 Igneous Rock Textures 279 Soil Classification 319 Identification of Igneous Rocks 279 SUMMARY 321 Chemistry of Igneous Rocks 283 Intrusive Bodies 284 Shallow Intrusive Structures 284 Intrusives That Crystallize at Depth 286 Abundance and Distribution of Plutonic Rocks 287 How Magma Forms 288 Heat for Melting Rock 288 The Geothermal Gradient and Partial Melting 288 Decompression Melting 288 Addition of Water 289 13 How Magmas of Different Compositions Evolve 289 Sequence of Crystallization and Melting 289 Mass Wasting 325 Differentiation 290 Partial Melting 292 Assimilation 292 Surficial Processes 325 Mixing of Magmas 292 Relationships to Earth Systems 326 Explaining Igneous Activity by Plate Tectonics 293 Introduction to Mass Wasting 326 Igneous Processes at Divergent Boundaries 293 Classification of Mass Wasting 327 Intraplate Igneous Activity 294 Rate of Movement 327 Igneous Processes at Convergent Boundaries 295 Type of Material 327 SUMMARY 297 Type of Movement 327 Controlling Factors in Mass Wasting 330 Gravity 330 Water 331 Triggers 332 Common Types of Mass Wasting 332 Creep 332 Flow 334 Rockfalls and Rockslides 338 Underwater Landslides 341 Preventing Landslides 346 Preventing Mass Wasting of Soil 346 12 Preventing Rockfalls and Rockslides on Highways 347 SUMMARY 348 Weathering and Soil 301 Weathering, Erosion, and Transportation 302 Weathering and Earth Systems 302 Atmosphere 302 Hydrosphere 302 Biosphere 303 How Weathering Changes Rocks 303 Effects of Weathering 304 14 Mechanical Weathering 304 Sediment and Sedimentary Rocks 351 Pressure Release 305 Frost Action 305 Other Processes 306 Relationship to Earth Systems 352 Chemical Weathering 306 Sediment 352 Role of Oxygen 307 Transportation 353 Role of Acids 308 Deposition 354 Solution Weathering 309 Preservation 355 Chemical Weathering of Feldspar 310 Lithification 355 Chemical Weathering of Other Minerals 311 Weathering Products 311 Types of Sedimentary Rocks 356 Factors Affecting Weathering 312 Detrital Rocks 356 Soil 312 Breccia and Conglomerate 356 Soil Horizons 313 Sandstone 357 Factors Affecting Soil Formation 315 The Fine-Grained Rocks 357 ccaarr6699440033__ffmm__ii--xxxxvv..iinndddd iixx 11//1188//1100 1100::5511::3388 PPMM