INSTRUCTOR’S MANUAL AND TEST BANK Essentials of Geology Fourth Edition Stephen Marshak Instructor’s Manual by John Werner SEMINOLE STATE COLLEGE OF FLORIDA Test Bank by Jacalyn Gorczynski TEXAS A&M UNIVERSITY– CORPUS CHRISTI Heather L. Lehto ANGELO STATE UNIVERSITY Daniel Wynne SACRAMENTO COMMUNITY COLLEGE B W • W • NORTON & COMPANY • NEW YORK • LONDON —-1 —0 —+1 5577-50734_ch00_2P.indd77-50734_ch00_2P.indd iiiiii 110/5/120/5/12 55:41:41 PPMM W. W. Norton & Company has been in de pen dent since its founding in 1923, when William Warder Norton and Mary D. Herter Norton fi rst published lectures delivered at the People’s Institute, the adult education division of New York City’s Cooper Union. The Nortons soon expanded their program beyond the Institute, publishing books by celebrated academics from America and abroad. By mid- century, the two major pillars of Norton’s publishing program— trade books and college texts— were fi rmly established. In the 1950s, the Norton family transferred control of the company to its employees, and today— with a staff of four hundred and a comparable number of trade, college, and professional titles published each year— W. W. Norton & Company stands as the largest and oldest publishing house owned wholly by its employees. Copyright © 2013, 2009, 2007, 2004 by W. W. Norton & Company, Inc. All rights reserved. Printed in the United States of America. Associate Editor, Supplements: Callinda Taylor. Project Editor: Thom Foley. Production Manager: Benjamin Reynolds. Editorial Assistant, Supplements: Paula Iborra. Composition and project management: Westchester Publishing Ser vices. Art by CodeMantra and Precision Graphics. Book design by Jack Meserole. Manufacturing by Sterling-Pierce—East Rockaway, N.Y. Special thanks to: Marek Cichanski, De Anza College Karen Koy, Missouri Western State University Judy McIlrath, University of South Florida ISBN 978- 0- 393- 92011- 6 (pbk.) W. W. Norton & Company, Inc., 500 Fifth Avenue, New York, N.Y. 10110 www .wwnorton .com W. W. Norton & Company Ltd., Castle House, 75/76 Wells Street, London W1T 3QT 1 2 3 4 5 6 7 8 9 0 -1— 0— +1— 5577-50734_ch00_3P.indd77-50734_ch00_3P.indd iviv 110/24/120/24/12 112:432:43 PPMM CONTENTS Instructor’s Manual Chapter 1 | The Earth in Context 3 Chapter 2 | The Way the Earth Works: Plate Tectonics 9 Chapter 3 | Patterns in Nature: Minerals 15 Chapter 4 | Up from the Inferno: Magma and Igneous Rocks 19 Chapter 5 | The Wrath of Vulcan: Volcanic Eruptions 24 Chapter 6 | Pages of Earth’s Past: Sedimentary Rocks 28 Chapter 7 | Metamorphism: A Process of Change 33 Chapter 8 | A Violent Pulse: Earthquakes 38 Chapter 9 | Crags, Cracks, and Crumples: Crustal Deformation and Mountain Building 43 Chapter 10 | Deep Time: How Old Is Old? 47 Chapter 11 | A Biography of Earth 53 Chapter 12 | Riches in Rock: Energy and Mineral Resources 58 Chapter 13 | Unsafe Ground: Landslides and Other Mass Movements 64 Chapter 14 | Streams and Floods: The Geology of Running Water 68 Chapter 15 | Restless Realm: Oceans and Coasts 73 Chapter 16 | A Hidden Reserve: Groundwater 79 Chapter 17 | Dry Regions: The Geology of Deserts 84 Chapter 18 | Amazing Ice: Glaciers and Ice Ages 89 Chapter 19 | Global Change in the Earth System 94 —-1 —0 —+1 v 5577-50734_ch00_2P.indd77-50734_ch00_2P.indd v 110/5/120/5/12 55:41:41 PPMM Instructor’s Manual —-1 —0 —+1 5577-50734_ch01_2P.indd77-50734_ch01_2P.indd 1 110/5/120/5/12 55:40:40 PPMM The Way the Earth Works: CHAPTER 2 Plate Tectonics Learning Objectives 1. Students should be aware of Wegener’s amassed evidence for continental drift. The fi t of coastal outlines and the distribution of rocks, fossils, and ancient climatic belts all strongly suggest that the continents were once aligned to form a supercontinent named Pangaea. Wegener’s ideas had few supporters during his lifetime at least in part because he could not provide a workable mechanism through which continents could move with respect to one another. 2. During the twentieth century, paleomagnetic data showed that continents must have drifted, because the rocks of isolated continents produce unequal apparent polar- wander paths for the north magnetic pole. 3. Continents are passively pushed by the activity of sea- fl oor spreading, in which molten rock rises at mid- ocean ridges, cools to form new oceanic crust, and spreads laterally. Simultaneously, crust (and mantle lithosphere) is pulled downward and engulfed at deep- ocean trenches. 4. Sea- fl oor spreading was proven in the late 1960s by examination of marine magnetic anomalies, which are symmetric about the mid- ocean ridges. Combined with age dating, these patterns clearly show that oceanic crust is created at the ridges and spreads outward, with crustal age increasing away from the ridge axis in either direction. Areas of positive anomaly (including the ridges themselves) arise from rocks that crystallized and cooled during times when Earth’s magnetic polarity was normal (the same as it is today); rocks producing negative anomalies cooled during times of reversed polarity. 5. Together, the evidence for sea- fl oor spreading and continental drift have been combined with geophysical observations to form the basis of our modern understanding of plate tectonics— the unifying theory of geology that explains the distribution of earthquakes, volcanism, and mountain building, and the links among these phenomena. 6. The “plates” of plate tectonics are discrete slabs of lithosphere (crust and rigid portion of the mantle) that move with respect to each other. They glide over a ductile layer of —-1 the mantle termed the asthenosphere. Boundaries between plates are convergent (where —0 —+1 9 5577-50734_ch01_2P.indd77-50734_ch01_2P.indd 9 110/5/120/5/12 55:40:40 PPMM 10 | Chapter 2 plates move toward each other), divergent (where plates are pushed apart at a mid- ocean ridge), or transform (where plates slide past each other). Relative plate motions are on the order of a few centimeters a year (a common analogy is that these rates approximate the rate of human fi ngernail growth). 7. Plate motion at all three boundary types triggers earthquakes. Plate boundaries are delineated by belts of high historical earthquake frequency. 8. Volcanism is associated with both convergent (volcanic arcs) and divergent (mid- ocean ridges) boundaries but not transform boundaries. 9. Only oceanic lithosphere is dense enough to be subducted at convergent boundaries. When continental lithosphere is pushed (by a ridge) and pulled (by a leading edge of subducting oceanic lithosphere) into another continent, a mountainous collision zone is formed, and the two plates involved become sutured together. Conversely, a single large plate can become rifted apart when its lithosphere is stretched, thinned, and broken apart by a developing ridge. Summary from the Text Alfred Wegener proposed that continents had once been joined together to form a single huge supercontinent (Pangaea) and had subsequently drifted apart. This idea is the continental drift hypothesis. Wegener drew from several different sources of data to support his hypothesis: (1) the correlation of coastlines; (2) the distribution of late Paleozoic glaciers; (3) the distribution of late Paleozoic climatic belts; (4) the distribution of fossil species; and (5) correlation of distinctive rock assemblages now on opposite sides of the ocean. Rocks retain a record of the Earth’s magnetic fi eld that existed at the time the rocks formed. This record is called paleomagnetism. By mea sur ing paleomagnetism in successively older rocks, geologists discovered apparent polar- wander paths. Apparent polar- wander paths are different for different continents. Continents move with respect to one another, while the Earth’s magnetic poles remain roughly fi xed. Around 1960, Harry Hess proposed the hypothesis of sea- fl oor spreading. According to this hypothesis, new sea fl oor forms at mid- ocean ridges, above a band of upwelling mantle, then spreads symmetrically away from the ridge axis. Eventually, the ocean fl oor sinks back into the mantle at deep- ocean trenches. Magnetometer surveys of the sea fl oor revealed marine magnetic anomalies. Positive anomalies, where the magnetic fi eld strength is greater than expected, and negative anomalies, where the magnetic fi eld strength is less than expected, are arranged in alternating stripes. Geologists documented that the Earth’s magnetic fi eld reverses polarity every now and then. The record of reversals, dated by isotopic techniques, is called the magnetic- reversal chronology. A proof of sea- fl oor spreading came from the association of marine magnetic anomalies with the reversal chronology and from drilling studies proving that the sea fl oor gets progressively older away from a mid- ocean ridge. -1— The lithosphere, the rigid outer layer of Earth, is broken into discrete plates that move 0— relative to each other. Plates consist of the crust and the uppermost (cooler) mantle. +1— 5577-50734_ch01_2P.indd77-50734_ch01_2P.indd 1010 110/5/120/5/12 55:40:40 PPMM The Way the Earth Works: Plate Tectonics | 11 Lithosphere plates effectively fl oat on the underlying soft asthenosphere. Continental drift and sea- fl oor spreading are manifestations of plate movement. Most earthquakes and volcanoes occur along plate boundaries; the interiors of plates remain relatively rigid and intact. There are three types of plate boundaries— divergent, convergent, and transform— distinguished from one another by the movement the plate on one side of the boundary makes relative to the plate on the other side. Divergent boundaries are marked by mid- ocean ridges. At divergent boundaries, sea- fl oor spreading produces new oceanic lithosphere. Convergent boundaries are marked by deep- ocean trenches and volcanic arcs. At convergent boundaries, oceanic lithosphere of the downgoing plate subducts beneath an overriding plate. Transform boundaries are marked by large faults at which one plate slides sideways past another.