Plate Tectonics

ACKNOWLEDGMENTS

The idea for this project emerged from the History Committee of the American Geophysical Union (AGU), then chaired by Ed Cliver. For some time, the AGU has been committed to the importance of history as a resource for the scientific community. With its commitment to publications, oral history, and historically oriented themes at annual meetings, the AGU has been a model of what history can do for a scientific community, bringing diverse specialists together in ways that the daily practice of science rarely does. Beyond expressing our thanks to the AGU as an organization, we are particularly indebted to Ed Cliver. The idea for this project was Ed’s, and he convinced us to take it on. Moreover, he stayed involved every step of the way: helping to identify and track down contributors, calling to check progress, reading manuscripts, and providing moral support and good humor all along the way.

We also wish to express our appreciation for the 17 scientists whose essays appear in this volume. When we began this project, we did not know how our invitees would respond, and we had some concerns that they might be dismissive of history, as scientists sometimes are. This turned out not to be the case. On the contrary, our authors responded with enthusiasm and made time in their busy lives to take on this extra task. Each of them has been a pleasure to work with, and we have learned a great deal from our interactions with them. Nearly every one of our authors took additional time to help resolve discrepancies in the historical record; to discuss historical, philosophical, personal, and political questions raised by the history of plate tectonics; or to send us relevant reprints, photos, and interviews. To each and every one of them we are extremely grateful. We owe a special debt of gratitude to Xavier Le Pichon, Dan McKenzie, Peter Molnar, and Jack Oliver for extended conversations and email communications, and to local colleagues at the Scripps Institution of Oceanography (SIO) John Sclater and Bob Parker for their constant willingness to help clarify technical points. Jason Morgan and Ted Irving were unable to write essays for this volume, but generously gave of their time to talk about their contributions. We are grateful also to SIO archivist Deborah Day, whose professional title scarcely does justice to the myriad ways she supports and promotes historical understanding, not only at SIO, but throughout the earth sciences community.

Several colleagues read manuscripts and provided feedback at various stages in the project—Kenneth Belitz, Ron Doel, Gary Ernst, Fred Spiess, Norm Sleep, Ken Taylor, Gary Weir, and David van Keuren. Throughout the project, Duncan Agnew has been ever-ready and willing not only to read and comment on materials, but even to go to the library to find the reference that would resolve a question to which no one else knew the answer (or in some cases even where to look). The depth and breadth of his knowledge is nothing short of remarkable, and on more than one occasion he has saved us from embarrassing mistakes.

No work can be done without logistical support, and we wish to express our gratitude to SIO director Charles Kennel for his generosity in providing seed money for the larger project on the history of oceanography, of which this volume is a part, and ever-precious office space. Equally important is the ongoing support of colleagues in the Science Studies Program at the University of California, San Diego (UCSD), for creating a community interested in diverse approaches to understanding science and its role in all of our lives. I am particularly indebted to Robert Westman for deepening my appreciation of what it means to be a historian, my understanding of why history is so worth doing.

Several UCSD students worked on this project at various stages, and we need to thank Andrea Santos, Sue Kim, Brook Mangin, and Katie Atwood, and above all the inestimable James Peters, who simply did everything that needed to be done.

A book is only a pile of papers without an editor and a press, and here we have more than the usual debts to acknowledge. This project was originally signed at Columbia University Press, and we are grateful to Director William B. Strachan for releasing us from our contract and permitting us to move the project to Westview Press along with our editor and publisher, Holly Hodder. It is difficult to describe the work that Holly has done on this project without lapsing into platitudes. Suffice it to say that she has been there every step of the way: editing, talking, brainstorming, cajoling, supporting, encouraging. She has never wavered from her commitment to the importance, significance, and meaning of this project, never wavered from her belief that earth science is exciting, important, and worth knowing.

Naomi Oreskes

La Jolla, California, July 2001

Homer Le Grand,

Melbourne, Australia, 2001

PREFACE:
HISTORY AND MEMORY

HISTORIAN JACQUES LE GOFF HAS WRITTEN THAT THE JOB OF history is to correct memory.¹ If so, then this book is not a work of history. The essays presented here are works of memory, stories told by scientists whose work changed the way we think about the planet we live on. Before the 1960s, there was no generally accepted global theory to explain the major features of the earth: the continents and oceans, the mountains and valleys, the volcanoes and earthquakes. In the 1960s, a new theory emerged that explained all this and more as the result of the interactions of moving pieces of the earth’s surface layer, henceforth to be known as tectonic plates. While the development of plate tectonics was a long time in coming – scientific evidence of continental mobility had been recognized since the early 20th century – its acceptance was rapid and nearly absolute. By the early 1970s, virtually all earth scientists accepted the new theory and textbooks were rewritten.²

It has been more than 30 years since the events retold here. When we invited the authors to write for this volume, we asked them to tell their stories as best as they could recall and to reflect on their significance with the benefit of hindsight. The authors were young when they did the work described here, and considerable time has elapsed. All of the authors are brilliant and creative people, and their scientific careers did not end with the contributions they made to plate tectonics. They all continued to work as scholars and teachers, some remaining in the specialties they began in, others shifting their focus. Our authors have had to reach back in time to write these essays, and the resulting stories are works of memory, not history. If memory is faulty – and we all know that it is – then why bother with it? One recent psychological study suggests that accurate memory of adolescent experience is no better than what might be expected by chance.³ So why not simply write history, and correct memory?

There are at least three reasons why the essays in this volume are important contributions that complement histories written by professional historians.⁴ The most obvious is that, while memory is often faulty, it is not always faulty. People do remember important and formative events in their lives, sometimes in extraordinary detail, and they often remember connections that are not recorded elsewhere. While historians prefer to rely on written documents, which are less readily subject to subsequent distortion or manipulation, contemporary documents are not always available. Even when they are, documentation is selective: many things are never written down, and most of what is written down is not saved.

The written record is most silent about the lives of ordinary people, and social historians have come to reply on oral accounts to capture the voices of people whose lives might otherwise go unheeded. However, the authors of these essays are not ordinary people – indeed, they are quite extraordinary – and their scientific work is amply documented in their published papers. Scientific research by its nature leaves an ample paper trail. But in their own way, scientific papers are as incomplete as any political or social records. While they recount the evidence and arguments at stake, they omit much of what is of human interest: how people came to their discoveries and insights and how they felt about them. Moreover, as historian Steven Brush pointed out some years ago, scientific papers are deliberately incomplete, if not downright misleading.⁵ Scientific papers are written as if their authors knew from the start where they were heading and saw all along where the data were leading. The false starts, the misinterpretations, the wasted efforts, the failed experiments – these are almost always expunged from published reports. Philosopher Hans Reichenbach called this the “rational reconstruction of knowledge” – how it should have happened in a perfect world, if everything had been done right from the start.⁶ The result is a picture of science and scientists as far more efficient than they really are. Because rational reconstruction is the norm for scientific reporting, many scientists follow this pattern even when speaking off the record, perpetuating the image of scientists as coldly rational, even robotic.

Beyond the cognitive cleansing that occurs in scientific publications, there is also an emotional cleansing: feelings are left out. Science is supposed to be about what we know, not about how we feel. Scientific papers are written as if the authors had no feelings about the matters under discussion (or anything else, for that matter).⁷ They are written as if the authors didn’t care about the outcome of their work.⁸ Yet surely they do care, or why would they work so hard? Why would they call their col-xii leagues – as Tanya Atwater vividly recounts – at 2 A.M. to discuss their latest idea?

If scientists’ accounts of their work are drained of emotion, popular accounts often err in the opposite direction, painting scientific work as a steady stream of dramatic discovery. To anyone who has ever done scientific research, such accounts ring equally false as their reverse. The stories told here attempt to strike a realistic middle ground: to recount the genuine excitement their authors felt as they became involved in one of the great scientific developments of the 20th century, while conveying the frustrations and false starts as well. As important and true as Tanya Atwater’s unbridled excitement is Xavier Le Pichon’s poignant portrayal of the moment his world collapsed, as he realized that everything he had written in his just-finished Ph.D. dissertation was wrong.

A second reason for presenting these essays is to gather a multiplicity of perspectives in a single volume. Several of our authors have written about their work before, but never have their differing perspectives been presented together in one place. And their perspectives are indeed different. The 17 scientists who tell their stories here became scientists for different reasons, approached their work in different ways, and made important contributions by different means. As they look back now on their work, they come to various (and not always reconciliable) conclusions. One author – Gordon MacDonald – candidly recounts his objections to plate tectonics in the 1960s, which, he argues, have still not been adequately answered. As editors, we have not attempted to enforce a uniform style or to reconcile opposing views. We have done our best to correct errors on factual matters, but beyond that we have sought to preserve the diverse voices of our authors as an important part of the unique value of this volume.

While the value and legitimacy of multiple perspectives has become widely accepted in many fields – art, architecture, literature, history – in science we are still wedded to the notion of the right answer. While there is a single right answer to certain kinds of technical questions – How old is the earth? What is the composition of the sun? – many scientists extend the presumption of a single right answer to questions in philosophy of science: How does science advance? What is the correct scientific method? What makes a scientist great? (As if these were comparable questions to what the radius of the earth is!) The essays in this volume argue against a narrow answer to these kinds of questions. Some of the stories told here involve data-driven science, others involve conceptual or mathematical innovation, still others involve novel instruments and data analysis. Likewise, if one were to ask, “what kind of a personality does it take to succeed in science?” the answer provided by this volume would have to be multiple. The authors of these essays are unique and diverse individuals, and it would be no more possible to say what unites them than to say what unites all great artists or all wonderful mothers.

This leads to the third and most important reason for presenting these essays: the scientists writing in this volume speak with the voice of experience. Each of the authors has had time to consider his or her own scientific life and contributions. Each has, in some way, been forced into such consideration by the prominence of his or her contributions (or, in Lawrence Morley’s case, by the poignancy of seeing someone else become famous for an idea that he also had, but saw rejected for publication at two leading scientific journals). By the nature of our sample – scientists writing about events 30 years later – these are people who made major contributions early in their scientific careers. All have had the opportunity to work on other things, to make contributions in other areas, and to reflect on what made the 1960s such a special time to be an earth scientist. Psychiatrist Daniel Offer and his colleagues call memories a form of “existential reconstruction” – a means by which people make sense of their lives.⁹ The stories presented here are the sense that 17 distinguished scientists have made of their scientific lives. They may not be works of history, but they may well be works of wisdom.

MANY INDIVIDUALS, BUT ONLY A FEW INSTITUTIONS

Besides the insights from individual stories, there are patterns that emerge from the collective whole. Perhaps the most striking feature of the development of plate tectonics is the small number of institutions but large number of individuals involved. The bulk of the story told here takes place at only four institutions worldwide: Cambridge University, Columbia University’s Lamont Geological Observatory, the University of California’s Scripps Institution of Oceanography, and Princeton University. ¹⁰ A striking feature of the stories in this volume is how many of the players moved back and forth among Cambridge, Lamont, Princeton, and Scripps, and how data-sharing facilitated the rapid development of ideas, and idea-sharing facilitated the effective interpretation of data. Keith Runcorn brought the work of British paleomagnetism to the attention of scientists at Lamont; Dan McKenzie, Robert Parker, and John Sclater brought their physics-oriented Cambridge training to Scripps; Harry Hess brought his idea of sea floor spreading to the atten-xiv tion of Fred Vine at Cambridge. And so on. Research thrives where smart people can work together and share data and ideas.

The concentration of intellectual and material resources in these institutions was also self-perpetuating. Several of our authors had personal connections that helped them get to these places: a father who also studied at Cambridge, another father who was a physicist who knew geophysicists at Lamont. The importance of personal ties helps to explain why only a very few women, and no African Americans, appear in these stories: in the early 1960s women and African Americans were not admitted to graduate study at Princeton, and only begrudgingly at Scripps; the available evidence suggests the situation was similar at Cambridge and Lamont.¹¹ As Tanya Atwater makes clear in her essay, the women who made it to these places had to maintain their good humor despite numerous slights and petty obstacles. Atwater did her best to focus on the work she loved, ignoring the fact that many of the people around her considered her a “freak.”

In contrast to the small number of institutions, the development of plate tectonics involved a large number of individuals. Seventeen of them tell their stories here; there could have been many more. Many key players have passed away: P. M. S. Blackett, Sir Edward Bullard, Drummond Matthews, and Keith Runcorn in Great Britain; Allan Cox, Robert Dietz, Bruce Heezen, Harry Hess, Bill Menard, and Tuzo Wilson in North America. As editors, we struggled with limitations of time and space and the need to balance contributions from scientists representing different institutions and specialties. Our solution, albeit an imperfect one, was that if a group of scientists worked together on a project, we generally asked only one of them to tell the story. Lamont alumni will therefore notice the absence of Jim Heirtzler, Lynn Sykes, Bryan Isacks, and Marie Tharp; their absence should by no means be read as a negative judgment on the importance of their work. Finally, some whom we invited (although only a very small number) declined to participate, being busy with other things. All in all, there are at least three dozen individuals who could easily be counted as major contributors to the development of plate tectonics, still more if we extend our view to include the recognition of its implications for continental geology and earth history.¹²

This raises a significant historical point. We tend to link scientific advance to scientific genius, which by definition is individual. When most of us think of the great advances in the history of science, we think of great names – Copernicus, Newton, Darwin, Einstein. An earlier generation of historians often labeled scientific advances by the names of the individuals credited with them: the Copernican Revolution, the Darwinian revolution. Certainly, simple labels are convenient. But when historians scratch the surface of scientific discovery, they usually find many scientists working around a topic. Often other individuals have either hit upon the same ideas or evidence as their more famous counterpart (think of Alfred Russell Wallace and Charles Darwin) or have been awfully close to it. So we might ask, is plate tectonics different than other major scientific advances in involving so many individuals? Or is it simply that time has yet to obscure the details?

Perhaps the large number of individuals involved in the development of plate tectonics is a function of the time when these events took place. The 1950s and 1960s were a period of unprecedented funding for scientific research, particularly in the United States, where much of the critical work of plate tectonics was accomplished. (Several of the British scientists whose work is discussed in this volume received funding from the U.S. Office of Naval Research.) As is well known, the expansive federal funding of American science in the 1950s coupled with the G.I. Bill, which greatly increased the numbers of individuals in higher education, dramatically boosted the number of American scientists.¹³ Moreover, military funding of scientific research in aid of national security often involved large laboratories and team-oriented approaches.¹⁴ This implies that, other things being equal, it is likely that discoveries in the 20th century will involve more people than discoveries in earlier centuries.

There is also something in the nature of these discoveries that helps to explain why so many people were involved. Plate tectonics is a global theory – the first global theory ever to be generally accepted in the entire history of earth science.¹⁵ Putting it together was a work of synthesis, involving data of many kinds from many places. While Ron Mason and Walter Pitman were making paleomagnetic measurements of rocks on the sea floor, Lawrence Morley was making similar measurements on land, Jack Oliver and Bruce Bolt were analyzing seismic data from earthquakes, and John Sclater was measuring heat flow over the mid-ocean ridges. What made plate tectonics so compelling was the way it unified these different kinds of data from all parts of the earth. Unlike some kinds of theoretical arguments in physics or laboratory experiments in chemistry, which might conceivably be achieved by an individual, there is simply no way all this work could have been done by one person, or even a small handful of persons.

Moreover, many of the critical data of plate tectonics were collected on oceanographic expeditions, as the essays by Mason, Pitman, Opdyke, Atwater, and others recount. Organizing these expeditions was a major undertaking, and every expedition involved many scientists, as well as technicians and crew. People also worked behind the scenes: beforehand to make the expeditions happen, afterward to compile, catalogue, and preserve the data. Frequently lurking in the background of our story is Maurice Ewing, the tireless director of the Lamont Geological Observatory, whose relentless pursuit of data – and the financing that kept his ships at sea almost continuously for two decades – made possible much of what is recounted here. Roger Revelle played a similar role at Scripps, but Revelle had diverse interests, and Scripps was far less systematic in its pursuit and cataloguing of data. This difference proved significant: when critical ideas were put forth, it was Lamont more than any other institution that was in a position to test them, to make sense of them, and to prove them right or wrong.

The importance of expeditions and their organization points to a second theme that emerges from these essays: the role of data – lots and lots of it. In history, philosophy, and sociology of science it has become routine to say that observations are “theory-laden,” and that people can be resistant to information that fails to fit their cognitive frameworks. On many accounts, conceptual innovation is a prerequisite not merely to the reinterpretation of data, but even to its recognition. One popular rendition of this view, sometimes emblazoned on T-shirts, reads “If I hadn’t believed it, I wouldn’t have seen it.” Philosophers of science in the mid-to late 20th century virtually abandoned the idea that observation could drive science, and focused instead on the role of hypotheses or theories in guiding observation, suggesting tests.

While conceptual innovation was an important part of the development of plate tectonics, the stories told here strongly suggest that the most powerful driving force was data. By his own account, Harry Hess was driven to develop the idea of sea floor spreading – that new ocean crust is generated at mid-ocean ridges, where the ocean floor splits apart, driving the motions of the continents – by the paleomagnetic data collected by British geophysicists Keith Runcorn, Ted Irving, P. M. S. Black-ett, and their colleagues. These data showed that the continents had been moving, sometimes separately, sometimes together, throughout geological history. The evidence that this was so preceded the conceptual explanation of how it was so.

Paleomagnetic data also drove the further development of Hess’ idea. As Ron Mason recounts in his essay, in the late 1950s and early 1960s, Arthur Raff, Victor Vacquier, and he were collecting magnetic data on rocks of the sea floor off the coast of California primarily because the U.S. Navy was interested in paleomagnetism for its relevance to submarine detection; scientists, largely because it was there. When Mason and Raff discovered a distinctive pattern of “magnetic stripes” – zones whose magnetic polarity was the same as the present-day earth field, paralleled by zones whose polarity was opposite – they were frankly at a loss for how to explain them, and they said so in their published work. Others took up the challenge. As Lawrence Morley recounts, the “zebra pattern” was so peculiar, so unexplained, that it caused him to drop what he was doing to focus on interpreting its meaning. Fred Vine did the same. Dan McKenzie and John Sclater argue that it was precisely this, data that people acknowledged must be right, but could not be explained by available theory, which drove earth scientists toward a new explanation, however unlikely it had seemed at the outset of their investigations. In the development of plate tectonics, recalcitrant data drove conceptual innovation.