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ORIGIN AND EVOLUTION OF EARTH RESEARCH QUESTIONS FOR A CHANGING PLANET Committee on Grand Research Questions in the Solid-Earth Sciences Board on Earth Sciences and Resources Division on Earth and Life Studies
The National Academies Press 500 Fifth Street, N.W. Washington, DC 20001 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This study was supported by the National Science Foundation, Award No. EAR-0533650; National Aero- nautics and Space Administration, Award No. NNH06CE15B, TO #104; U.S. Department of Energy, Award No. DE-FG02-05ER15664; and U.S. Department of Interior / U.S. Geological Survey, Award No. 05HQGR0138. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project. International Standard Book Number-13:â 978-0-309-11717-3 (Book) International Standard Book Number-10:â 0-309-11717-3 (Book) International Standard Book Number-13:â 978-0-309-11718-0 (PDF) International Standard Book Number-10:â 0-309-11718-6 (PDF) Library of Congress Catalog Number:â 2008929776 Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu. Cover:â Selection of scales and disciplines relevant to Earth science. Top: Artistâs conception of an emerging solar system around the star Beta Pictoris. Courtesy of Lynette R. Cook and the National Aeronautics and Space Administration. Bottom right: Outcrop of Neoproterozoic (750-800 million years old) platform car- bonates (left) and subjacent interbedded carbonaceous shales and stromatolitic carbonates (right) exposed by receding glacier, northeastern Spitsbergen. Courtesy of Andrew Knoll, Harvard University. Bottom middle: A spherical-global view (orthographic projection) of the western hemisphere 105 million years ago. Courtesy of Ronald Blakey, Northern Arizona University. Bottom left: Ground motion intensities for a simulated magnitude 7.7 earthquake on the San Andreas Fault in the Los Angeles area. Visualization courtesy of Amit Chourasia and Steve Cutchin, San Diego Supercomputer Center, University of California, San Diego, based on data provided by Kim Olsen and colleagues, Southern California Earthquake Center. Back: Repeated images of the crystal structure of stishovite, a mantle mineral that can store water in Earthâs interior. Courtesy of Lars Stixrude, University of Michigan. Copyright 2008 by the National Academy of Sciences. All rights reserved.
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COMMITTEE ON GRAND RESEARCH QUESTIONS IN THE SOLID- EARTH SCIENCES DONALD J. DePAOLO, Chair, University of California, Berkeley THURE E. CERLING, University of Utah, Salt Lake City SIDNEY R. HEMMING, Columbia University, Palisades, New York ANDREW H. KNOLL, Harvard University, Cambridge, Massachusetts FRANK M. RICHTER, The University of Chicago LEIGH H. ROYDEN, Massachusetts Institute of Technology, Cambridge ROBERTA L. RUDNICK, University of Maryland, College Park LARS STIXRUDE, University of Michigan, Ann Arbor JAMES S. TREFIL, George Mason University, Fairfax, Virginia National Research Council Staff Anne M. Linn, Study Director JARED P. ENO, Research Associate
BOARD ON EARTH SCIENCES AND RESOURCES GEORGE M. HORNBERGER, Chair, University of Virginia, Charlottesville GREGORY B. BAECHER, University of Maryland, College Park KEITH C. CLARKE, University of California, Santa Barbara DAVID J. COWEN, University of South Carolina, Columbia WILLIAM E. DIETRICH, University of California, Berkeley ROGER M. DOWNS, The Pennsylvania State University, University Park JEFF DOZIER, University of California, Santa Barbara KATHERINE H. FREEMAN, The Pennsylvania State University, University Park RUSSELL J. HEMLEY, Carnegie Institution of Washington, Washington, D.C. MURRAY W. HITZMAN, Colorado School of Mines, Golden LOUISE H. KELLOGG, University of California, Davis CLAUDIA INÃS MORA, Los Alamos National Laboratory, New Mexico BRIJ M. MOUDGIL, University of Florida, Gainesville V. RAMA MURTHY, University of Minnesota (retired), Minneapolis CLAYTON R. NICHOLS, Idaho National Engineering and Environmental Laboratory (retired), Standpoint RAYMOND A. PRICE, Queenâs University, Kingston, Ontario, Canada BARBARA A. ROMANOWICZ, University of California, Berkeley JOAQUIN RUIZ, University of Arizona, Tucson WILLIAM W. SHILTS, Illinois State Geological Survey, Champaign RUSSELL E. STANDS-OVER-BULL, Anadarko Petroleum Corporation, Billings, Montana TERRY C. WALLACE, Jr., Los Alamos National Laboratory, New Mexico HERMAN B. ZIMMERMAN, National Science Foundation (retired), Arlington, Virginia National Research Council Staff ANTHONY R. de SOUZA, Director ELIZABETH A. EIDE, Senior Program Officer DAVID A. FEARY, Senior Program Officer ANNE M. LINN, Senior Program Officer SAMMANTHA L. MAGSINO, Program Officer CAETLIN M. OFIESH, Associate Program Officer VERNA J. BOWEN, Administrative and Financial Associate JENNIFER T. ESTEP, Financial Associate JARED P. ENO, Research Associate NICHOLAS D. ROGERS, Research Associate TONYA E. FONG YEE, Program Assistant vi
Preface O ver the past four decades, Earth scientists and the Association of Women Geoscientists. Written have made great strides in understanding our input was also gathered from colleagues. The commit- planetâs workings and history. We understand tee met four times to gather input, discuss community as never before how plate tectonics shapes our planetâs feedback, and write its report. surface, how life can be sustained over billions of years, A small committee cannot hope to have all the and how geological, biological, atmospheric, and oce- expertise needed to cover the broad range of topics dis- anic processes interact to produce climateâand cli- cussed in this report. Consequently, the committee solic- matic change. Yet at the most basic level, this progress ited essays from colleagues. Of particular note were the has served principally to lay bare more fundamental essays provided by Greg Beroza, Katharine Cashman, questions about Earth. Expanding knowledge is gen- and Kevin Zahnle. Other colleagues who devoted many erating new questions, while innovative technologies hours helping the committee sort through ideas include and new partnerships with other sciences provide new Alan Anderson, Richard Bambach, Katherine Freeman, paths toward answers. James Kasting, Barbara Romanowicz, Sean Solomon, The Committee on Grand Research Questions and Mary Lou Zoback. The committee is deeply ap- in the Solid-Earth Sciences was established at the preciative of their contributions. The committee also request of the U.S. Department of Energy, National thanks the many other individuals who provided input Aeronautics and Space Administration, National Sci- or feedback on the questions: Richard Allen, Paul ence Foundation, and U.S. Geological Survey to frame Barton, Steven Benner, David Bercovici, Robert Berner, some of the great intellectual challenges inherent in Robert Blair, Jr., Gudmundur Bodvarsson, Alan Boss, the study of Earth and other planets. Although many Gabriel Bowen, Susan Brantley, Douglas Burbank, reports have identified research priorities in Earth sci- Frank Burke, Kenneth Caldeira, Richard Carlson, ence, few have cast them as compelling, fundamental John Chambers, Frederick Colwell, Kevin Crowley, science questions. Such âbig pictureâ questions may Gedeon Dagan, Andrew Davis, William Dickinson, require decades to answer and research support from William Dietrich, David Diodato, Bruce Doe, Robert many agencies and organizations. The answers to these Dott, Jr., Benjamin Edwards, Peter Eichhubl, Michael questions could profoundly affect our understanding of Ellis, W. Gary Ernst, Douglas Erwin, Rodney Ewing, the planet on which we live. Fredrick Frey, Arthur Goldstein, Linda Gundersen, The committee began by drafting âstrawmanâ David Halpern, Wayne Hamilton, T. Mark Harrison, questions and publishing them for comment in Eos, John Hayes, James Head, Michael Hochella, Jr., Transactions of the American Geophysical Union (Linn, Vance Holliday, Richard Iverson, A. Hope Jahren, 2006), on the National Academies website, and in elec- Raymond Jeanloz, Gerald Joyce, Joseph Kirschvink, tronic newsletters of the American Geological Institute John LaBrecque, Thorne Lay, Antonio Lazcano, vii
viii PREFACE Cin-Ty Lee, William Leeman, Jonathan Lunine, Ernest Soreghan, Frank Spear, Gary Sposito, Steven Stanley, Majer, Michael Manga, Anthony Mannucci, William Ross Stein, Robert Stern, David Stevenson, Lynn McDonough, Dan McKenzie, Marcia McNutt, H. Jay Sykes, Jack Szostak, Thomas Tharp, Leon Thomsen, Melosh, Peter Molnar, Isabel Montanez, Alexandra Oliver Tschauner, Terry Tullis, Greg Valentine, Navrotsky, Shlomo Neuman, Gary Olhoeft, Carolyn Richard Von Herzen, Joseph Wang, James Whitcomb, Olson, Peter Olson, Minoru Ozima, Nazario Pavoni, Raymond Willemann, M. Gordon Wolman, Nicholas Donald Porcelli, Jonathan Price, Steven Pride, George Woodward, Eva Zanzerkia, Xiaobing Zhou, and Redden, Paul Renne, Robin Reichlin, Mark Richards, Herman Zimmerman. Daniel Schrag, Norman Sleep, D. Kip Solomon, Gerilyn Donald J. DePaolo, Chair
Acknowledgment of Reviewers T his report has been reviewed in draft form by Jay Melosh, University of Arizona individuals chosen for their diverse perspec- Franklin Orr, Stanford University tives and technical expertise, in accordance Norman Sleep, Stanford University with procedures approved by the National Research Steven Stanley, University of Hawaii Councilâs Report Review Committee. The purpose of David Stevenson, California Institute of this independent review is to provide candid and criti- Technology cal comments that will assist the institution in making Robert van der Hilst, Massachusetts Institute of its published report as sound as possible and to ensure Technology that the report meets institutional standards for objec- tivity, evidence, and responsiveness to the study charge. Although the reviewers listed above have provided The review comments and draft manuscript remain many constructive comments and suggestions, they confidential to protect the integrity of the deliberative were not asked to endorse the conclusions or recom- process. We wish to thank the following individuals for mendations nor did they see the final draft of the report their participation in the review of this report: before its release. The review of this report was overseen by Marcia McNutt, Monterey Bay Aquarium Research Douglas Erwin, Smithsonian Institution Institute. Appointed by the National Research Council, Jonathan Fink, Arizona State University she was responsible for making certain that an inde- Jeffrey Freymueller, University of Alaska pendent examination of this report was carried out in Russel Hemley, Carnegie Institution of accordance with institutional procedures and that all Washington review comments were carefully considered. Respon- Thomas Jordan, University of Southern sibility for the final content of this report rests entirely California with the authoring committee and the institution. Louise Kellogg, University of California, Davis Rosamond Kinzler, American Museum of Natural History ix
Contents SUMMARY 1 1 ORIGINS 7 Question 1: How did Earth and other planets form? 7 Question 2: What happened during Earthâs âdark ageâ (the first 500 million years)? 18 Question 3: How did life begin? 27 2 EARTHâS INTERIOR 35 Question 4: How does Earthâs interior work, and how does it affect the surface? 35 Question 5: Why does Earth have plate tectonics and continents? 50 Question 6: How are Earth processes controlled by material properties? 60 3 A HABITABLE PLANET 71 Question 7: What causes climate to changeâand how much can it change? 71 Question 8: How has life shaped Earthâand how has Earth shaped life? 84 4 HAZARDS AND RESOURCES 95 Question 9: Can earthquakes, volcanic eruptions, and their consequences be predicted? 95 Question 10: How do fluid flow and transport affect the human environment? 111 REFERENCES 123 APPENDIXES A Biographical Sketches of Committee Members 133 B Acronyms and Abbreviations 137 xi