Plate Tectonics, Volcanoes, and Earthquakes (Dynamic · PDF file7 Plate Tectonics, Volcanoes, and Earthquakes 7 16 as “burning mountains.” Today, it is commonly known that volcanoes

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  • ISBN 978-1-61530-106-5

  • Published in 2011 by Britannica Educational Publishing (a trademark of Encyclopdia Britannica, Inc.)in association with Rosen Educational Services, LLC29 East 21st Street, New York, NY 10010.

    Copyright 2011 Encyclopdia Britannica, Inc. Britannica, Encyclopdia Britannica, and the Thistle logo are registered trademarks of Encyclopdia Britannica, Inc. All rights reserved.

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    First Edition

    Britannica Educational PublishingMichael I. Levy: Executive EditorJ. E. Luebering: Senior Manager Marilyn L. Barton: Senior Coordinator, Production ControlSteven Bosco: Director, Editorial TechnologiesLisa S. Braucher: Senior Producer and Data EditorYvette Charboneau: Senior Copy EditorKathy Nakamura: Manager, Media AcquisitionJohn P. Rafferty: Associate Editor, Earth Sciences

    Rosen Educational ServicesAlexandra Hanson-Harding: EditorNelson S: Art DirectorCindy Reiman: Photography ManagerNicole Russo: DesignerMatthew Cauli: Cover DesignIntroduction by Therese Shea

    Library of Congress Cataloging-in-Publication Data

    Plate tectonics, volcanoes, and earthquakes / edited by John P. Rafferty. p. cm.(Dynamic Earth)In association with Britannica Educational Publishing, Rosen Educational Services.Includes index.ISBN 978-1-61530-187-4 ( eBook)1. Plate tectonics. 2. Volcanoes. 3. Earthquakes. 4. Geodynamics. I. Rafferty, John P.QE511.4.P585 2010551.8dc22


    Cover, pp. 12, 82, 302 Grondin; p. 22 Torfason; pp. 23, 307; pp. 202, 305 Shi


    Introduction 12

    Chapter 1: Earths Dynamic Interior 23

    The Process of Plate Tectonics 24Principles of Plate Tectonics 26 Continental and

    Oceanic Crust 27 Plate Boundaries 28 Hot Spots 38 Plate Motion 40 The Development of Tectonic Theory 42 The Precursors of

    Modern Thinking 43 Alfred Wegener and

    the Concept of Continental Drift 44

    The Renewed Interest in Continental Drift 48

    Toward a Unifying Theory 54 Dissenting Opinions and

    Unanswered Questions 58Plate Tectonics and the Geologic Past 62 The Wilson Cycle 62 The Supercontinent Cycle 65 Continental

    Reconstructions 66





  • The Interaction of Tectonics with Other Systems 67 Earths Oceans 68 Life 69 Earths Climate 72Other Concepts Related to Plate Tectonics 74 Continental Drift 74 Diastrophism 78 Isostasy 78 Orogeny 81 Tectonics 81

    Chapter 2: Volcanoes and Volcanism 82

    Volcanic Eruptions 86 Lava, Gas, and Other

    Hazards 86 Six Types of Eruptions 100 Two 20th-Century

    Eruptions 104 The Four Worst Eruptions

    in History 111 Volcano Forecasting and

    Warning 113 Major Volcanoes of

    the World 114 Signifi cant Volcanoes of

    the World 128 Mount Agung 128 Askja 128 Mount Aso 129 Mount Cameroon 130 Cotopaxi 131 Mount Etna 132 Mount Fuji 134

    Mount Hekla 135





  • Mount Hood 137 Iraz Volcano 138 Izalco Volcano 139 Kilauea 139 Klyuchevskaya

    Volcano 142 Krakatoa 143 Lassen Peak 145 Mauna Loa 146 Mayon Volcano 148 Mount Unzen 148 Mount Nyamulagira 149 Mount Nyiragongo 150 Ol Doinyo Lengai 150 Paricutn 151 Pavlof Volcano 151 Mount Pele 152 Volcano Pico de

    Orizaba 153 Mount Pinatubo 154 Popocatpetl 154 Mount Rainier 155 Mount Ruapehu 157 Mount Ruiz 159 Mount Saint Helens 159 Tajumulco Volcano 164 Mount Tambora 164 Teide Peak 165 Vesuvius 166Volcanic Landforms 169 The Major Types of

    Volcanic Landforms 169 The Determinants of

    Size and Shape 179 Hot Springs and Geysers 182 Cross Section of a

    Geyser and Hot Spring 184





  • Volcanism and Tectonic Activity 186 Volcanoes Related to

    Plate Boundaries 186 Volcanic Activity and the

    Earths Tectonic Plates 188 Intraplate Volcanism 190Volcanoes and Geothermal Energy 191Related Concepts 193 Bomb 193 Fumarole 194 Kimberlite Eruption 194 Magma 196 Mofette 197 Volcanic Winter 197 Volcanism 199 Volcanology 201

    Chapter 3: Earthquakes 202The Nature of Earthquakes 203 The Causes of

    Earthquakes 204 The Eff ects of

    Earthquakes 210 The Intensity and Magnitude

    of Earthquakes 214 Modifi ed Mercalli Scale

    of Earthquake Intensity 215 The Occurrence of

    Earthquakes 220 Notable Earthquakes

    in History 224Signifi cant Earthquakes 231 The Aleppo Earthquake

    of 1138 232 The Shaanxi Province

    Earthquake of 1556 232




  • The Lisbon Earthquake of 1755 233

    The New Madrid Earthquakes of 181112 234

    The Messina Earthquake and Tsunami 236

    The Tokyo-Yokohama Earthquake of 1923 236

    The San Francisco Earthquake of 1906 237

    The Chile Earthquake of 1960 238

    The Alaska Earthquake of 1964 238

    The Ancash Earthquake of 1970 239

    The Tangshan Earthquake of 1976 240

    The Mexico City Earthquake of 1985 240

    The San FranciscoOakland Earthquake of 1989 240

    The Northridge Earthquake of 1994 241 The Ko-be Earthquake of 1995 243

    The Izmit Earthquake of 1999 246

    The Taiwan Earthquake of 1999 247

    The Bhuj Earthquake of 2001 247

    The Kashmir Earthquake 248 The Sichuan Earthquake

    of 2008 248 The Haiti Earthquake

    Of 2010 249




  • The Study of Earthquakes 250 Seismic Waves 251 The Observation of

    Earthquakes 259 Earthquake Prediction 263 The Exploration of Earths Interior with Seismic

    Waves 270 Extraterrestrial Seismic

    Phenomena 278Related Concepts 279 Circum-Pacifi c Belt 279 Fault 280 Types of Faulting in

    Tectonic Earthquakes 281 Richter Scale 283 Richter Scale of

    Earthquake Magnitude 284 Seismic Belt 285 Seismic Survey 285 Seismograph 286 Noted Thinkers 294 Beno Gutenberg 294 Sir Harold Jeff reys 295 Augustus Edward

    Hough Love 296 John Michell 297 John Milne 298 Harry Fielding Reid 299 Charles F. Richter 299 The Scope of Tectonic Forces 300

    Glossary 302For Further Reading 305Index 307






  • A volcano erupts on the island of Runion in the Indian Ocean. Grondin

    Humans live on unsteady ground. This fact was made abruptly apparent on January 12, 2010, when a magnitude 7.0 earthquake devastated the Caribbean island nation of Haiti. Because many buildings in this impoverished country were poorly constructed, they could not withstand the shaking and collapsed en masse, particularly in the capital city of Port-au-Prince, 15 miles from the quakes epicenter. Rescue workers des-perately combed through rubble, hunting for survivors. By early February, Haitis prime minister estimated that more than 200,000 people had been killed by the earthquakes effects. This type of earthquake, caused by two separate sections, or plates, of the Earths crust sliding against each other is known as a strike-slip earthquake. It is just one example of the restlessness of Earths surface.

    This book will show how the movement of rock within the Earth is explained by the theory of plate tectonics, the idea that Earths outer layer is broken into moving pieces. It will show how Earth adds and subtracts land over time. In addition, it will explain how and why volca-noes erupt and earthquakes shake the ground we live on.

    As early as 1620, scholars noticed that the outlines of continents could fi t together like puzzle pieces. In 1912, German scientist Alfred Wegener fi rst explained the concept of continental drift. He postulated that a single supercontinent, which he called Pangea, once existed, but broke apart into several pieces over geologic time.Wegener cited the existence of similar types of rocks and fossils found from separate continents as proof. He also used continental drift to explain the evidence of major climate and biological changes.

    7 Introduction 7


  • 7 Plate Tectonics, Volcanoes, and Earthquakes 7


    By the late 1960s, scientists had pieced together the how of plate tectonics. Earths crustthe top layer of the lithosphereis broken into pieces called plates. The plates rest on and slide over a layer of plastic and molten rock. As the plates move, they shape the features of Earths surface above, including continents and oceans. Movement takes timea mere 5 to 10 cm (2 to 4 inches) per year in some places, less in others. Hundreds of millions of years have passed since Pangea began to separate into the land masses we know today.

    The surface of each tectonic plate is made up of continental crust and oceanic crust. The continental crust is less dense and thus floats higher than oceanic crust. It is also about 40 km (25 miles) thick. While oceanic crust averages about 6.4 km (4 miles) thick. Tectonic plates interact at convergent, divergent, and transform boundaries.

    When the boundary of oceanic crust meets, or con-verges with, continental crust, the more buoyant continental crust stays afloat while the oceanic crust is forced beneath ita process called subduction. The subducting crust melts under the pressure and heat of Earths mantle, and the process offers an explanation of why continental crust is generally older than oceanic crust. When two oceanic plates meet, the older plate subducts under the younger one. In contrast, when two continental crusts meet, neither gives w