National Academies Press: OpenBook

Energetics of the Earth (1980)

Chapter: Front Matter

Suggested Citation:"Front Matter." National Research Council. 1980. Energetics of the Earth. Washington, DC: The National Academies Press. doi: 10.17226/9579.
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Suggested Citation:"Front Matter." National Research Council. 1980. Energetics of the Earth. Washington, DC: The National Academies Press. doi: 10.17226/9579.
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Suggested Citation:"Front Matter." National Research Council. 1980. Energetics of the Earth. Washington, DC: The National Academies Press. doi: 10.17226/9579.
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Suggested Citation:"Front Matter." National Research Council. 1980. Energetics of the Earth. Washington, DC: The National Academies Press. doi: 10.17226/9579.
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(~.~}:= it'' i- :' 1 JOHN VERHOOGEN University of California, Berkeley Energetic so the Earthy NATIONAL ACADEMY OF SCIENCES Washington, D.C. 1980 Hi'

The National Academy of Sciences was established in 1863 by Act of Congress as a private, non-profit, self-governing membership corporation for the furtherance of science and technology, required to advise the federal government upon request within its fields of competence. Under its corporate charter the Academy established the National Re- search Council in 1916, the National Academy of Engineenng in 1964, and the Institute of Medicine in 1970. Library of Congress Cataloging in Publication Data Verhoogen, John, 1912 Energetics of the Earth. Bibliography: p. Includes index. 1. Earth temperature. 2. Earth-Internal structure. I. Title. QE509.V45 551.1'2 80-17501 ISBN ~309 0307~5 Available from National Academy Press National Academy of Sciences 2101 Constitution Avenue, N.W. Washington, D.C. 20418 Printed in the United States of America

Preface This is the text, somewhat enlarged, of a series of four lectures deliv- ered at Stanford University in January 1979 by the happy recipient of the 1978 Arthur L. Day Prize and Lectureship of the National Academy of Sciences. Funds are earmarked for publication of the lectures, which according to the terms of the award should "prove a solid, timely and useful addition to the knowledge and literature in the field." Whether the lectures will prove to be solid, timely, or useful is as uncertain as their topic. This topic, which has been of great interest to me for more than 40 years, remains largely speculative. Progress has been slow; there is not so terribly much more to say about temperature at the core-mantle boundary than Francis Birch said in 1952 in his celebrated paper on the constitution of the earth's interior. As the reader will readily perceive, there is still room for considerable differ- ence of opinion on almost every subject. Much of the uncertainty stems from our ignorance of physical prop- erties of terrestrial materials at pressures of a few megabars, such as exist in the lower mantle and core. One may hope that much more information will become available in the next few years, now that static experiments appear feasible in the megabar range. On the other hand, our understanding of thermal events at the time of, or shortly after, formation of the earth will remain speculative for many years to come, as also will the crucial matter of the abundance of radioactive elements in the mantle and core. On the theoretical side, perhaps the greatest step forward in the last four decades or indeed since the discovery of . . .

iY Preface radioactivity-has been the recognition of convection as the dominant mode of heat transfer in most of the mantle and core. Here, at long last, is something to hang on to. The writer wishes to express deep thanks to all his colleagues at Berkeley who have helped him throughout the years, and particularly to the graduate students who have discussed these matters with him in seminars. He is grateful also to the audience at Stanford University for their warm welcome, and to Professor Allan Cox for the perfection of the arrangements. Berkeley, March 1979

Contents 1 ENERGY SINKS Heat Flow, 2 Volcanic Heat, 4 Metamorphic Heat, 5 Strain Energy; Earthquakes, 7 Potential Energy; Uplift of Mountains, 8 Plate Tectonics, 8 Kinetic Energy of Rotation, 11 Summary, 13 2 ENERGY SOURCES Original Heat, 15 Gravitational Energy, 18 Core Formation, 19 Tidal Friction, 21 Radiogenic Heat, 23 Crustal Heat Versus Mantle Heat, 26 Summary, 28 3 TEMPERATURES WITHIN THE EARTH The Upper Mantle, 31 The Low-Velocity Zone, 31; Geotherms from Nodules in Kimberlite, 33 1 15 29

vi Contents The Mantle's Transition Zones, 35 The Lower Mantle, 36 Layer D', 36; Layer D", 44 The Outer Core, 49 Composition of the Core, 49; Temperature from an Equation of State The Adiabatic Gradient, 54 , 52; The Temperature at the Inner Core-Outer Core Boundary, 56 The Melting Point of Iron, 56; Melting in the Fe-S System, 60 Summary, 65 4 DYNAMICS OF THE CORE Stability of the Core, 68 Causes for Convection, 70 Energy Requirements of the Geomagnetic Dynamo, 70 Efficiency of a Steady-State Thermal Dynamo, 75 An Improved Estimate of Efficiency, 78 The Entropy Balance Equation, 83 The Gravitational Dynamo, 88 Gravitational Energy, 89; Volumetric Relations, 91; Heat Output of Core, 95 5 CORE-MANTLE INTERACTIONS Efficiency of the Mantle, 100 Convection Patterns in the Mantle, 104 67 100 Convective Pattern for Distributed Sources of Heat, 104; Heat from the Core, 110 Additional Factors in Controlling the Flow, 112 Temperature Dependence of Physical Properties, 112; The Von Zeipel Insta- bility, 112; Ejects of Surface Plates, 114; Effects of Phase Transitions in the Mantle, 114 Influence of the Core on Convection in the Mantle, 118 Influence of the Mantle on Convection in the Core, 120 Some Final Remarks, 121 REFERENCES AUTHOR INDEX SUBJECT INDEX 125 133 137

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