Brent Dalrymple

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ORAL HISTORIES
Brent Dalrymple

Photo courtesy of Brent Dalrymple

Interviewed by
David Zierler
Interview date
Location
Video conference
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Interview of Brent Dalrymple by David Zierler on June 7, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/46964

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Interview with G. Brent Dalrymple, Dean and Professor Emeritus at Oregon State University. Dalrymple recounts his childhood in Los Angeles, and he explains how he settled on geology as a major at Occidental and the impact of the plate tectonics revolution that was happening at the time. He discusses his graduate work at Berkeley, and he recounts his field work under the direction of Garniss Curtis on potassium argon dating. Dalrymple explains his decision to join the U.S. Geological Survey after graduate school and his interest in learning more about volcanic rocks and magnetic fields in the Sierra range. He explains how this research solved the problem of continental drift and he discusses his subsequent research on the Hawaiian Island range. Dalrymple discusses his work on earthquake detection, and he describes the advances in K-Ar dating and techniques. He discusses his work on meteorite dating and the light this shed on what killed off the dinosaurs, and he describes his advisory work for the Apollo missions. Dalrymple explains how he became involved in debates with religious communities who insisted the age of the Earth was 6,000 years old and how this turned into his book The Age of the Earth. He describes how geo-dating is relevant for understanding star and galaxy formation and he discusses his tenure as president of the American Geophysical Union. Dalrymple describes what it was like to win the National Medal of Science, and he explains his decision to retire from the USGS and join the administration at Oregon State. At the end of the interview, Dalrymple describes the impact of continental drift research, and he conveys his enjoyment with life in retirement.

Transcript

Zierler:

OK, this is David Zierler, Oral Historian for the American Institute of Physics. It is June 7, 2021. I am delighted to be here with Professor G. Brent Dalrymple. Brent, it's great to see you. Thank you for joining me.

Dalrymple:

Oh, you're most welcome.

Zierler:

To start, would you please tell me your title and institutional affiliation?

Dalrymple:

I'm Dean and Professor Emeritus at Oregon State University.

Zierler:

And in what ways, since you've been emeritus, have you remained connected with Oregon State?

Dalrymple:

Mostly through sports and philanthropic donations, that sort of thing. I'm of the firm belief that once you reach retirement age, you've just got to get out of the way and leave the academics to the younger people. So that's exactly what I've done.

Zierler:

What about on the research side? What have you been involved with in the past years in terms of science?

Dalrymple:

Absolutely nothing. I finished a book and a couple papers right after I retired in 2001, and that was the end of my career in science.

Zierler:

So, this is a true retirement that you're enjoying.

Dalrymple:

It was a true retirement. I don't review things, I don't do any consulting, I don't even keep up with the literature.

Zierler:

So, what have you been up to in the past 20 or so years? What do you do for enjoyment?

Dalrymple:

Oh, lots of things. A few, I can’t do now because of orthopedic reasons. But my wife and I both enjoyed downhill skiing and playing golf, we used to do a lot of that. I have a wood shop, I do a lot of woodworking, mostly making things that are completely useless, but I like to look at. And since 1956, I've been a pilot. So, I took up flying again after I retired, and I gave that up again about four or five years ago. I was kind of losing my edge and didn't want to be a hazard to anyone, especially flying in the clouds and the ATC system. So now, I mostly just read and do woodworking. And I would tell you that we've been enjoying visiting our kids and grandkids, but that's been off the list for the last year and a half, because of the pandemic.

Zierler:

I know you're not keeping up with the literature as you say, at least on a technical level, but what about the treatment in more popular journals in fields relating to geology and planetary science? What's been going on more broadly, as you see it?

Dalrymple:

I can't tell you; I don't keep up with that either.

Zierler:

So, it's a complete retirement.

Dalrymple:

Well, yes. When I was first hired at the US Geological Survey, Charlie Anderson was the chief geologist. And after he stepped down from that position after many years, he moved to Menlo Park, and I got to know him a bit. Charlie retired at 65, I think. And one day, I asked him why he was retiring. He didn't seem to me to be all that old. And he said, "Well, I've always been of the firm impression that once you reach retirement age, you're probably not doing anything useful anyway. And you're very expensive." And as I said a few minutes ago, Charlie added, "Get out of the way and leave the money and space to the younger people." And that's exactly what I've done.

Zierler:

Well, one value that you can certainly provide is to give us some historical perspective on the field since you began in it. So, with that, let's go all the way back to the beginning in Alhambra, California. We'll start with your parents. Tell me a little bit about them and where they're from.

Dalrymple:

That's complicated. My biological father and mother were married about 1929 or '30. I was born in '37. And they divorced either just before or just after I was born. So, I didn't know my biological father. I guess I met him a couple times when I was a tyke, but that was about it. Then, my mother remarried in 1944, I think it was, to a guy by the name of Don Dalrymple, who ended up adopting me a few years later, and my name was changed from Clayton to Dalrymple at that time. And he was the one who actually raised me, taught me how to hunt, and fish, and so forth.

Zierler:

What were your family's experiences during the Great Depression? Did they suffer?

Dalrymple:

I don't know. I really don't know what it was. As far as I know, they didn't suffer like a lot of people did. They still had jobs and I think did OK.

Zierler:

And what was your mom's work, if she worked outside of the house, and your adopted father's profession?

Dalrymple:

She did work outside of the house. She was a secretary for the manager of the Edison Company in Huntington Park for many years.

Zierler:

And your adopted father?

Dalrymple:

He was a brick contractor. He was a brick layer and a contractor. He built industrial buildings.

Zierler:

What early memories do you have of World War II, or at least the United States being in war?

Dalrymple:

I remember blackouts, when you had to cover up all your windows with cloth so the light wouldn't come through for air raids. At that time, we lived in Alhambra, California, and after my mother remarried in Bell, California, so we were fairly near the coast throughout the war.

Zierler:

This was out of concern for Japanese attacks.

Dalrymple:

The blackouts, yes. And I remember block wardens coming around to make sure that you had everything all buttoned up. I remember when we drove, the top half of our headlights were covered up. And I think there may have been a curfew, too. I remember my mother saving bacon grease because that was turned in to the butcher shops and used for something. Or maybe not, I don't know. [laugh] I remember ration coupons for things like butter, meat, and gasoline. Since my father was a contractor, he had essentially unlimited gas coupons. So, we could trade gas coupons for butter, and meat, and other things that were rationed. So, we didn't have much of a problem getting the things that everyone desired. I remember that butter was mostly unavailable and margarine was the only substitute you could buy. The margarine was white, and you had to color it yourself so it couldn't be counterfeited. They had a little color packet in there, so you could make it yellow if you wanted. We always did because white margarine looked kind of disgusting on food.

And then, I do remember air raids. I don't think anything came out of them at that particular time, but I remember sirens going off and having to wait inside for a while. And I remember when the War ended–and I don't remember whether it was the end of the War in Europe or in Japan, but I remember going downtown to pick up my aunt, who was working down there and couldn't get home because there wasn't any transportation. People were all over the streets, having a big party. I was about 7 or 8 then. But I can remember people hanging off the streetcars, and celebrating, and just having a good old time.

Zierler:

Did you go to public schools throughout your childhood?

Dalrymple:

I did, yes.

Zierler:

Did you have a strong curriculum in math and science in high school?

Dalrymple:

Well, not as strong as it is today. Bell High School was in the Los Angeles School District, and you had courses in mathematics up through geometry, algebra, trigonometry. No calculus. Calculus wasn’t taught in most high schools in those days. You could take a couple years of physics, which I did. They had chemistry class. And one of the big differences was there were shop classes that boys had to take. There was a metal shop, wood shop, auto shop, electrical shop, plumbing shop, sheet metal shop. And I think you had to pick three or four of those as part of the curriculum. I graduated in a class of ‘63 from Bell High School, in February. The Los Angeles School District at that time had both February and June graduations. And of that class of ‘63, only seven of us had taken the curriculum necessary to apply to college. So that'll give you a little view into what it was like. Bell was essentially a lily-white, blue collar town at the time. It no longer is. So, there was enough science and math to get me into college.

Zierler:

Now, did you have any nascent interest in geology as a boy that would've foreshadowed your career, like collecting rocks?

Dalrymple:

None, whatsoever. In fact, I thought that was what geologists did, collected rocks. And I thought, "What a dumb thing to do." [laugh] So no, I was more interested in physics or perhaps engineering.

Zierler:

So how is it that you settled on geology at Occidental?

Dalrymple:

Well, I started out as a physics major, and I had to take two other science classes, so I picked geology. I didn’t have any particular reason to do that, I just didn’t know anything about it, so I thought I would learn. The professor teaching the beginning course was Joe Birman, who was a really charismatic speaker. And he got me excited about the earth. And I found out that studying the earth was a lot more than collecting rocks. So, I went in to talk to Joe and ask him about switching from physics. And he was telling me some of the interesting problems that still existed in geology at the time, like how mountains erode, for example. Do they erode from the top down or from the sides inward? There were some really simple problems to which no one knew the answers.

And so, I thought, "Well, that sounds kind of fun." My dad was a hunter, and I always liked camping, and being outdoors. So, I thought maybe that would be a good switch for me to make. So, I asked Joe, “How are jobs in geology?” And he said, “Oh, they’re just terrible. You can’t get a job right now for love nor money.” And I said, “Well, that doesn’t sound very good.” And he says, “No, no, it’s very good. They tend to go in seven- or eight-year cycles.” Most of the jobs were in the oil or mining industries at that time. “By the time you get through graduate school,” Hope said, “you won't have any trouble getting a job." And he turned out to be right.

Zierler:

Now, given your early interest in physics, would geophysics have been a way to square the circle? Was that a field of study that would've been available at that point in time?

Dalrymple:

It would have, and eventually I did square the circle in some ways. But that wasn't part of my thought process at the time.

Zierler:

What were some of the big research questions in geology at that point when your professor turned you onto all of the things that you could've done, at least academically?

Dalrymple:

Well, let me tell you some of the things that were different at the time. I was educated on both sides of the plate tectonics revolution, and I’ve always thought that was a really fortunate thing.

Zierler:

Now, when you say both sides, what was the early side, and what was the later side?

Dalrymple:

Well, that’s what I want to tell you. When I was a student in undergraduate school and graduate school, for example, the oceans were considered the oldest features on the earth. And they were going to be a source of great mineral wealth. And after plate tectonics, we learned that, in fact, they were the youngest features on the earth, aside from individual volcanoes and features like that, and that they were not a great source of mineral wealth. We didn’t know why certain things existed, like the Appalachian Mountains, for example. Why were they there? Well, there were all kinds of goofy explanations, but it just turns out that that’s where two continents banged together over 400 million years ago. And that’s something that plate tectonics told us. Continental drift was a huge debate. There was some evidence that the continents had drifted. The shapes between the continents on either side of the Atlantic Ocean looked like they should fit together, and a lot of the geology and paleontology carries right across from one continent to another. It looked like it should’ve been continuous.

But at that time, the big barrier to accepting that was the fact that continents have deep roots, and you could not push a continent through the mantle because Earth’s mantle is very viscous. Regardless of what kind of force you put on it, it just would not work. So, this was a great debate. Plate tectonics solved that problem. Alfred Wegener proposed continental drift back in the 1920s, and a lot of people think that scientists ignored it. But my experience was just the opposite, that it was debated very heavily, at least at Berkeley, where I went to graduate school. You could see the evidence for it, and you could also understand the physics that precluded it. And not until plate tectonics came along did the solution become obvious, that is, that the continents were not plowing their way through the mantle but riding on thick lithosphere plates that were sliding over the deep mantle.

Zierler:

What kinds of technological advances made the plate tectonic revolution possible?

Dalrymple:

Well, some of it was increased exploration at sea. And outfits like NOAA towing magnetometers around without really knowing why they were doing it, but making these beautifully colored magnetic maps of the sea floor. A lot of the advances involved techniques for measuring ages because that turned out to be important for the geomagnetic reversal time scale and other things. Measuring the ages of rocks and minerals required the development of equipment to measure isotopes very precisely. And most of those revolutions came about, like, in the 50s and early 60s. And so, part of what lead to the plate tectonics revolution was the ability to measure things that needed to be measured in order to solve certain problems in geophysics and geology.

Zierler:

Did you have a senior thesis at Occidental or any formative laboratory or observational work as an undergraduate?

Dalrymple:

No, not really. I worked for a summer for the department chairman, Joe Birman, in his consulting business in New Mexico, exploring for titanium beach sand deposits in the cretaceous sandstones. That got me interested in magnetism because mostly, the work involved making magnetic maps over potential deposits. But there was no senior thesis and no particular research that I did there. I didn't really form a research goal until well into Berkeley.

Zierler:

What kind of advice, if at all, did you get about what the best programs were to apply to at the time?

Dalrymple:

For graduate school, it was more of a decision about where would be convenient to go and what might be affordable. I only applied to two places, Stanford and Berkeley, and I got into both. But Stanford didn't provide any financial assistance. And Berkeley, at the time, didn't have any tuition. So, that was a fairly obvious choice.

Zierler:

Staying on the West Coast was a priority for you.

Dalrymple:

Yeah. When I was applying to colleges, I applied to Caltech, MIT, and Occidental College, and I got into MIT and Oxy. Caltech didn't admit me, which turned out to be a really good thing for me.

Zierler:

Why do you say that?

Dalrymple:

Well, it's always seemed to me that Caltech tends to grind up their undergraduates pretty thoroughly. It's a great place for graduate school, but I'm sure I should not have gone there as an undergraduate, and I didn't want our kids to go there either. But MIT was so far away, and I just decided to go to Oxy. I had a cousin who went there, and she said it was a pretty good place. It turned out well because of the geology department, and mostly because that's where I met my wife.

Zierler:

What were some of the exciting things going on in the geology department at Berkeley when you joined?

Dalrymple:

Well, a number of things. John Verhoogen was there, and he had several students working on paleomagnetism. Allan Cox and Dick Doell were there before I was there, and eventually became my colleagues. They had come out of Verhoogen's lab and done a really remarkable job with a fairly new field. Lionel Weiss was a professor who dealt in structural analysis, which is an interesting field that essentially disappeared. It was a way of supposedly analyzing stresses on rocks. If they were folded, what directions did the forces come from? How were those forces generated? And you could see multiple generations of folding, but the idea of getting the kinematics of that right just never gelled.

And so, for decades, that field, as far as I can tell, has been totally dead. And then, Garniss Curtis and Jack Evernden were working on a brand-new isotope dating method, potassium argon dating, which had been started at Berkeley by John Reynolds in the physics department to work on meteorites. And that seemed to be exciting, too. Then, there were lots of faculty who had written the textbooks of the time, Turner and petrology, Williams and petrography, Adolf Pabst and crystallography. The faculty was a group of what you might call giants when I was there.

Zierler:

I'm curious if the American response to the launch of Sputnik and all of the increased funding for basic science rippled to your world, if you felt that there were opportunities that you might not have otherwise had.

Dalrymple:

Well, I guess I really don't know. If you had decent proposals, there was certainly adequate money to get from the National Science Foundation. It wasn't nearly as competitive as it is now. Right now, it's really tough for a young investigator to get funding out of the National Science Foundation, just because there are so many people applying. And at that time, it wasn't nearly as much of a problem. I had NSF fellowships when I was at Berkeley for three years. I got a small grant from the Geological Society of America. And none of those things were terribly difficult to get. I think Sputnik threw money at virtually all kinds of science. So, I don't doubt that I and people around me were helped by that, but there wasn't any direct influence that I could tell. It was more indirect.

Zierler:

What was the divide, if there was one, in geology between observation and experimentation on one hand and theory on the other?

Dalrymple:

I guess I really didn't see any divide at Berkeley. Theoretical geology isn't exactly a thing. Most of the theory comes from other fields, mechanics, kinematics, physics, chemistry, and so forth. The theories in geology, aside from plate tectonics, which turned out to be huge, were simple things like, in a sedimentary sequence that hasn't been disturbed, the youngest rocks were on top. That's really important, but it's not all that complicated either. And there are a number of simple things like that that are unique to geology. So, I mentioned structural analysis. That had a theoretical side, it just never panned out.

Zierler:

What was the process like of connecting with a graduate advisor?

Dalrymple:

In my case, it turned out to be a bit of serendipity. Every graduate student, regardless of who or where you came from, was required to take the Berkeley field course in the hills behind the university for one semester at least. So, I was with a group of, I don't know, maybe a dozen graduate students who had come into Berkeley from all parts of the US. And Chuck Meyers, a mining geologist, was the professor. He was an excellent mapper. And I learned a lot from him. But I must've impressed him in some way because he recommended me as an instructor for the summer field camp following my first year at Berkeley. The summer field camp had about three dozen students in it, and they were geology students from all over the country.

And it was eight weeks long or so. I was one of the instructors. The other three were Garniss Curtis, Jack Evernden, both professors at Berkeley, and Don Weaver, who was a professor from UC Santa Barbara. So, it was the four of us. We all lived in the same tent and spent a lot of time together. And that's where I got to talking to Garniss Curtis and Jack Evernden about potassium argon dating and isotopes, and got interested in that field. I essentially connected with Garniss Curtis in that summer field camp experience, where we were supervising students in the mapping course.

Zierler:

What was Curtis's style like as a mentor?

Dalrymple:

He was really good. He was very supportive. One of the things he told me when he'd agreed to take me on was, "What I want you to do is get your PhD in four years and get the hell out of here and make room for somebody else." Which was really good because that's essentially the same thing that Sharon, my wife, told me. "I want you out of there in four years, so we can move on." And he also said, "When you write your thesis, I want you to write it as a paper, or maybe two or three papers, so they can be published immediately. I don't want one of these long tomes that goes on and on forever." So, my thesis was only 120 pages or so.

Zierler:

And how did you develop the thesis topic? Was it related to Curtis's work?

Dalrymple:

Well, by the time it came time to choose a thesis topic, I'd really gotten into potassium argon dating and was getting very good at that. And then, the other person on my committee was Clyde Wahrhaftig. And Clyde was a professor who had previously worked for the US Geological Survey, and both Joe Birman and Allan Cox had worked for him at different times as field assistants. So, there was this connection from Oxy to Berkeley through Allan Cox, who was now at the US Geological Survey. Clyde was interested in geomorphology.

And so, in talking with Clyde and Garniss, we thought it might be interesting to see if it was possible to date lava flows on erosion surfaces in the Sierra Nevada and get some quantitative information about the uplift of the Sierra. And that sounded good to me because my work with Joe Birman in his consulting business had all been out in the desert in New Mexico, where it's hot and dry, and it can be rather miserable camping in the desert. I wanted a place that had water and trees. The Sierra sounded like a really good deal. And at that time, you could just take a little tin cup and drink from the streams. You can't do that anymore.

Zierler:

So, this is to say that most of your research was field work, it wasn't laboratory work.

Dalrymple:

No, most of it was laboratory work. You had to collect the samples, but it was the laboratory work that took most of the time. During a typical summer, I would spend maybe a month total in the field.

Zierler:

So, you collect the samples, you bring them to the laboratory. What do you do with the samples then?

Dalrymple:

Well, you're trying to find material that you think would be reliably datable. In other words, rocks or minerals that are weathered or altered are not closed systems anymore, and they've lost some of their parent or daughter isotopes, and you can't date them reliably. So, the first thing you have to do is bring them back, get thin sections cut, so you can look at them microscopically and see if everybody looks happy in there. And if that's the case, you might either separate minerals, or you might even date the whole rock if there's no alteration in it.

Zierler:

And what are the techniques that you have at your disposal to date the rocks?

Dalrymple:

Well, the potassium argon method required two measurements, the amount of potassium in the rock, which is simply a chemical analysis, and then the more difficult one was measuring the argon-40, the daughter product from the radioactive decay of potassium-40. And that required noble gas mass spectrometry, which was, at that time, very difficult because it had to be done under ultra-high vacuum. John Reynolds had developed a mass spectrometer made of all glass. The Reynolds glass mass spectrometer could be baked to 300 degrees centigrade and kept relatively clean and was pretty sensitive. So, the Reynold-type mass spectrometer what we had in the geology department. So, the most laborious part, other than mineral separation, if you needed to do that, was getting the argon out of the rock by melting the rock, getting it out, cleaning up the other gases, collecting the argon, putting it in the mass spectrometer, and analyzing the isotopes.

Zierler:

Perhaps you thought about this at the time, or at least later, but in what ways was your thesis research responsive to some of the broader questions in the field at that point?

Dalrymple:

Oh, I don't think it was. It was just targeted at the history of the Sierra Nevada.

Zierler:

But could you extrapolate those findings to make broader conclusions about the planet or the continent?

Dalrymple:

Not really, no.

Zierler:

Besides Curtis, who else was on your thesis committee?

Dalrymple:

Clyde Wahrhaftig, Don Savage from the paleontology department, and I think that was it.

Zierler:

Anything memorable from the oral defense? Any good questions that stick out in your memory?

Dalrymple:

I didn’t do a thesis defense, but every PhD aspirant had to undergo an oral qualifying exam before being admitted to candidacy, and those were brutal. At the time I was there, there was no prep for the oral exam. The faculty didn't do anything to prepare you other than what you learned in courses. So graduate students had a book of questions they passed around and added to if they could remember what they were asked. But you had a committee of five. It wasn't your thesis committee; it was a different committee. My committee was Jack Evernden, Adolf Pabst, the crystallographer, Don Savage, from the paleontology department, and there was another member from the geology department whom I can’t remember. And then, Professor Gwinn, a physical chemist from the chemistry department, from whom I had a course in thermodynamics. The Committee asked you questions for an hour or two, or three, or four— as long as they wanted. My exam was a couple of hours long.

And then, when you're done, they sent you outside to sit and stew by yourself while they made their decision. In my case, Professor Gwinn forgot to show up. He was kind of an absentminded professor type, and he just forgot. So, there were only the four of them, and after they had adequately grilled me, they sent me outside. I sat out there by myself for about 30 minutes. I just knew that I'd failed because they don't really leave people out there that long. I was wondering what else I could do. I figured I could always go back and work as a brick layer. I found that kind of challenging and fun. But it turned out what they were trying to decide was whether Gwinn should examine me separately, or whether the four of them could just pass me on their own. They finally decided they could pass me on their own, so they did that. And that was the end of it. But at the time, about 50% of the students who took their PhD oral exam in the Geology and Geophysics Department at Berkeley failed. They'd give a few a second chance, but most people got a master's degree instead and went on.

Zierler:

That must've been a big sigh of relief for you.

Dalrymple:

It was. And like I say, it was rather brutal. These days, faculties tend to take a lot better care of their PhD students. And nearly all departments now give students pre-exams to make sure that they've got the body of knowledge they expect, and if not, they'll suggest further courses, further reading, and so forth. They take care of students a little better than they did when I went through Berkeley.

Zierler:

What opportunities were available to you at that point, and do you remember from your undergraduate days the warning that you wouldn't get a job in the field?

Dalrymple:

[laugh] Oh, yeah, I did remember. But I had two solid job offers, one questionable job offer, and several more in the works. So, I had a choice. That doesn't happen these days. Now, you have to go off and get a post-doc or something. But jobs were fairly easy then. All the graduate students I knew who came out of Berkeley got jobs immediately.

Zierler:

And what did you ultimately choose?

Dalrymple:

The US Geological Survey.

Zierler:

What was exciting to you about that?

Dalrymple:

Well, I had met Allan Cox and Richard Doell at an informal field conference that was put on by King Hubber, a USGS geologist. There were about a dozen of us, I think. It was between my second and third year as a graduate student. So, I was invited to this little informal field conference because I was interested in volcanic rocks in the Sierra, and I could do isotope dating, which very few people in the country could do at that time. This little field conference included Allan Cox and Richard Doell, who both worked for the US Geological Survey at the time. One night, after dinner, sitting around the campfire, Allan and Richard spent a long time talking to me about geomagnetic reversals, about which I knew virtually nothing.

I knew reversals were thought to have happened, but not much else. Allan and Richard had designed an experiment to determine whether the earth's magnetic field had reversed, and if so, when. They could do the paleomagnetic part, but they had no way to determine the ages of rocks. I didn't realize it at the time, but I was being recruited. And when I finally got out, I got a job offer, even before I graduated, from Richard Doell to come and join him and Allan at the Geological Survey and work on the geomagnetic reversal problem. Which is what I did.

Zierler:

And what exactly was the problem, and why was the Geological Survey committed to solving it?

Dalrymple:

The problem was, it had been known for many years that volcanic rocks are good magnetic field recorders. That is, they maintain a record of the ambient magnetic field in which they form. And since the geomagnetic field is a global phenomenon, if you know what the magnetic field was like at one point, then you can calculate what the dipole field was like for the entire earth as a first approximation. In other words, where the north and south poles were. It'd been known for a long time, since the 1920s or so, that some volcanic rocks showed a direction that was not consistent with the current magnetic field, but a reverse magnetic field. In other words, north and south poles were reversed. So, there were two possibilities. One, that the earth's magnetic field had reversed, and the second possibility was that there was some mechanism in the rocks that caused them to require a magnetism that was opposite the direction of the field in which they cooled.

So that was the experiment. And there were two ways to approach it. One was to look at the rocks through a microscope and try to decide if there was something in the mineralogy that would require magnetism to be reversed. And the second thing was to gather rocks for a wide variety around the world and plot their magnetism against time. And if all the rocks of a particular time were normal and those of another time were all reversed, then that pretty much tells you that it was magnetic field phenomenon and not something in the rocks. So that was the experiment. It was a fairly simple one in concept, except at that time, measuring geologic ages and using rocks and paleomagnetism were all fairly labor intensive and state of the art technologically.

So, while it could be done, it was very time-consuming and there weren’t many labs in the world capable of conducting such an experiment. But Allan and Richard had good funding from the Geological Survey. Why the Geological Survey was interested was simply because Allan and Richard were interested. And they were respected enough in the Geological Survey that they were allowed to do pretty much whatever they wanted to do.

Zierler:

So, it sounds like the Geological Survey was good about supporting basic science.

Dalrymple:

They were. And in fact, throughout almost my entire career, I got to do pretty much whatever I wanted to do as well. Certain parts of the Geological Survey required dedication to programs. For example, topographic mapping—-that’s not a research problem but a task to be done. Geologic mapping is sort of research, but a lot of it's just getting down on paper what the distribution of the different kinds of rock on the Earth are and trying to understand what they represent. But there were some parts of the Geological Survey that simply hired people they thought could do forefront research, and then turned them loose and funded them. And I was fortunate enough to land in that pot with Richard and Allan.

Zierler:

In what ways was your graduate research relevant for this experiment, and to what extent was this a whole new world for you?

Dalrymple:

Well, my graduate research involved essentially measuring the ages of rocks. That was the important and most difficult part of it. And that's exactly what Allan and Richard needed to conduct this reversal experiment. So, it was very relevant. It was a key to what they thought should be done, and it was essentially a continuation of what I had been doing, just on a different problem.

Zierler:

Now, what were some of the assumptions about what would come as a result of the research? Was everybody totally open-minded? Or was there some pre-ordained feeling about what this experiment would say in the end?

Dalrymple:

Well, in the end, it would either prove that the magnetic field had reversed or not. If it had not, that was kind of the end of it. A negative result would have, essentially, put a huge monkey wrench into paleomagnetism. But if it turned out that the geomagnetic field had reversed, then what we hoped to do was to determine the time scale of reversals for about the last four million years. And the reason we went from zero to four million was because at that time, high-precision K-Ar ages had a precision of about 3%. And so, when you get back to four million years, you essentially lose your ability to start resolving shorter events.

Zierler:

How long did the experiment last? Were there any surprises along the way?

Dalrymple:

I think '63 to '66 was when all our major papers came out. At the end of that, we had a time scale that essentially agreed with magnetic stripes on the ocean floor, which turned out to prove seafloor spreading. So, we were able to show conclusively that the earth's magnetic field had reversed in the past, we were able to show that reversals happened irregularly and not periodically. There were some times when the earth's field switched poles and then switched back fairly rapidly, within 100,000 years or so. And then, there were times when it was stable for more than a million years.

Zierler:

What broader questions did this research answer?

Dalrymple:

Well, as it turns out, there were magnetic stripes on the seafloor that were called positive and “negative” magnetism. But it was really positive and reverse magnetism. The pattern that the magnetic stripes made on the ocean floor mapped right onto our geomagnetic time scale. So, these stripes were essentially the result of seafloor spreading. Hot material came up from the mantle and created new ocean crust, and as that new crust cooled, it recorded the magnetic field at the time. And what you had was a conveyer belt that was moving out, forming new magnetic stripes on either side of the ocean ridges. So, our geomagnetic time scale turned out to be one of the keys to plate tectonics, and the proof of seafloor spreading. The geomagnetic time scale has often been called the Rosetta Stone of the theory of plate tectonics.

Zierler:

What major debates did this resolve as a result?

Dalrymple:

Well, it solved the problem of continental drift. One of the things that plate tectonics told us was, you don't have to plow continents through the mantle. What's happening is, there are lithospheric plates, which include both mantle and crust, and these plates are a couple hundred kilometers thick. The plates are essentially sliding over a more amenable zone in the mantle. And so, the continents are really just riding on top of the plates. They're not plowing through the mantle. And that solved the big problem with continental drift. It showed that continental drift did happen in a physically realistic way. So that was probably one of the major and long-debated problems that plate tectonics solved.

Zierler:

What considerations were made, given the significance of these findings, about where to publish the paper or what conferences to present at?

Dalrymple:

Well, there were two main places that we presented papers orally, meetings of the Geological Society of America and the American Geophysical Union. Those were essentially the two big ones for the US, and probably for the world. And then, in journals, you're constrained sometimes by length limits. Some journals will only accept papers of a certain length. So, if you had a longer one, that would determine whether it went into the Journal of Geological Research rather than, say, Geophysical Research Letters, for example. But the consideration that we usually focused on was which journal could get it out the fastest. Because things were developing so quickly, and we did have some competition in the first year or two from Australia. So, we were trying to get our latest results in print as quickly as possible. And other people were waiting for our time scales, too. People working on seafloor magnetic anomalies were waiting to see if these things were going to match up or not. Because when we first started, we thought, "Well, maybe reversals are going to be periodic." And so, what we produced was a series of time scales of magnetic reversals, all of which were wrong until the very last one.

Zierler:

Given that these time scales, you're talking about a period of millions and millions of years, were there any applications to these findings? Were there any ramifications that made your findings relevant in the here-and-now?

Dalrymple:

Not that I can think of, no. The geomagnetic reversals are a long-term phenomenon. One of the things we thought might be useful, this was before plate tectonics even came into consideration, was that if you knew when the field was reversed and when it was normal, it might be useful as a mapping tool. For example, a geologist could take a magnetometer out in the field or collect samples, and if they measured a rock that had reverse magnetism, that would tell you it's not the same age as one that had normal magnetism. And that's not a very precise dating tool, but it gives you some information. So, we thought a time scale might be useful in that way. But other than that, the only reason we did that reversal experiment was just to learn whether the field had reversed or not. That seemed exciting enough.

Zierler:

Now, you say that there was a race to publish. Who were some of the other groups you were in competition with?

Dalrymple:

Well, there was only one. It was Ian McDougall at Australian National University. Ian had two different paleo-magnetists that he worked with at different times. And Ian was a friend as well. In fact, when I started learning potassium argon dating in my second year at Berkeley, you had to start learning how to hook two pieces of pyrex glass together because all the equipment was glass in order to achieve the ultra-high vacuum necessary. You had to be able to build some of the stuff yourself. So, Ian and I started on the same day. He was at Berkeley from ANU and had his PhD already. But he was there on a post-doc to learn how to do potassium argon dating. And while he was there, Jack Evernden was in Australia setting up a dating lab for him. So, Ian and I became really good friends. And then, competitors as well. Ian was also interested in dating volcanic rocks and one of the few people in the world who could do it well. So, it was primarily Ian for a couple years. But after the first year or two, we were well ahead of him.

Zierler:

And is this because it was just a good partnership? Was there access to instrumentation or technology that you had that they didn't?

Dalrymple:

No, it wasn't a technological thing. It was essentially resources, money, and number of people. There were the three of us. We had a machine shop that had two people in it. We could build anything we needed and quickly. We had three or four technicians to help separate minerals from rocks, and grind up rocks, and do the argon extractions, make the magnetic measurements, and that sort of thing. So, we essentially had a more vigorous operation than Ian did. He was essentially working by himself with a technician.

Zierler:

What was the next project? What did you take on after this was wrapped up?

Dalrymple:

I guess the next big one was the study of the Hawaiian Islands. There's a long chain of Hawaiian Islands, starting with the big island where Kilauea is, goes all the way out through Midway and includes some of the volcanoes underneath the sea, goes past Midway to Kure, which is the last island. Beyond Kure there's a bend in the volcanic chain, where it becomes the Emperor Seamounts. The Emperor seamount chain continues northward and disappears into the Aleutian Trench. So, it'd been proposed a number of years before that this was all one continuous chain of volcanoes, and once plate tectonics came along, people thought it was caused by movement of the Pacific plate over some kind of hotspot or melting spot in the mantle that was producing magma.

So, the question was, are these volcanoes all of the same type? Do they look chemically and structurally like Hawaiian volcanoes, the ones we know that are above the ocean? And do the ages continue to progress as you go west and north? And it was already known that the ages of the main Hawaiian Islands, the ones you go vacation on, progressed and got older from Hawaii to Kauai. But the rest of them were pretty much unknown. So, Richard and I spent a couple of weeks sampling some of the leeward islands, the ones that are wildlife refuges well beyond Kauai. That was an interesting camping experience, being left on some of those islands that are no more than rocks for several days, hoping the Coast Guard would come back and pick us up. And then, from there on, we started working with samples that had been dredged by oceanographic vessels from some of these seamounts.

And eventually, we ended up putting in a proposal for the ocean drilling program to drill cores and get samples from seamounts out around the bend, which we were successful at. This was not with Allan and Richard; they had left the Survey long before then. Dale Jackson and David Clague were the primary people I was working with at that time. So, it involved working on islands that are no more than rocks in the ocean, going to sea and getting dredge samples, trying to find dredge samples from existing collections, and eventually spending a couple months on the Glomar Challenger, drilling holes in some of the seamounts near and beyond the Hawaiian-Emperor Bend. It was a good experiment. It turned out that as far as we could trace it, the ages do progress as you go west and north around the bend. And the rocks that form those remote islands and seamounts are all very similar to Hawaiian rocks. They're easily identified as being very similar to Kilauea and Mauna Loa. So, it's all the same chain.

Zierler:

I'm curious how some of your research was relevant for earthquake prediction science.

Dalrymple:

Oh, I don't think any of it ever was.

Zierler:

You did testify, though, in the California legislature about these things.

Dalrymple:

We did. It was a joint commission between the two houses of the California legislature, and it was called the Bay Conservation and Development Study Commission, and they were concerned about filling in San Francisco Bay. Actually, it was that commission that got most of that land filling stopped. But at the time, about 30, 40% of San Francisco Bay had been filled in from what it was 100 years previously. So that was one question, just using up the Bay by filling it in and building things on it. The other question was, when you put fill into an environment like that, is it seismically stable? Is it a good idea to put buildings on that stuff or not? And at the time, the Geological Survey wasn't talking much about earthquakes. They felt that was kind of a forbidden subject to discuss publicly. They were doing seismology, they were studying earthquakes, but you didn't talk about hazards. That was considered politically dangerous.

So, my colleague, Marvin Lanphere, and I, being brash young kids at the time, right after the Alaskan earthquake, decided to see if we could get a little more notice for the problems of building on filled land. And we did testify to that legislative committee. The administrators of the Geological Survey had a conniption fit. But eventually, it turned them around. The Survey is now the primary source of information about hazards of all kinds. Earthquakes, volcanoes, landslides. So USGS not only study such phenomenon, but if there is an imminent hazard, they tell people about it, and they're very good at doing that. So, I think we had an impact, not because of any of our research, but just essentially making a loud noise about the potential hazards of water saturated, filled land during big earthquake.

Zierler:

Perhaps it's a naive question, but given that the Geological Survey did seismology research, and the clear public benefit to early warnings, why on earth – literally! – would the Geological Survey not want to share those findings with the public?

Dalrymple:

Well, I think they did, but there were political hazards as well. For example, if a developer wants to build a housing tract on filled land in the San Francisco Bay, which was the example we tackled, and the USGS would come out and say it's a hazardous thing to do, then the land owner, and the developers, and the construction people are going to get really mad. And they have influence with legislatures and congressmen. And I think that was the main problem the Survey faced, how do you deal with political blowback when you tell somebody that this building they want to build is on unsafe ground, whether it's a landslide, or saturated ground on filled land, or next to a volcano or what? So, the public good is obvious, and the environment is such that they can now do that. But at the time, the Survey was afraid that they would get into political trouble by doing economic damage in mentioning these hazards. And I think they finally figured out that no, the good overrode the bad.

Zierler:

Do you have a sense of whether this decision-making reverberated up the chain all the way to the Department of the Interior, or even the Executive Branch?

Dalrymple:

It got up to the director of the Survey. I don't know that it got any farther.

Zierler:

Was it a dramatic change? In other words, on one day, they weren't in this business, and on the next day, they were? Or did it happen over time?

Dalrymple:

It happened over a fairly short period of time, just a few years. I wasn't involved in that. My involvement was just in that one instance.

Zierler:

Even as an outside observer, what do you remember as that first time when the Geological Survey did issue a warning, and it was a good thing that they did?

Dalrymple:

Well, they've never been able to predict earthquakes. They can predict where, but they can't predict when. And that was a very difficult problem. But the first one that I remember it was involved in a little bit involved Long Valley caldera near Mammoth Lakes, California. There's an ancient caldera about 700,000 or 800,000 years old just a few miles east of Mammoth Lakes in California. The area around that caldera started to swell, and to show some seismic activity. And both of those things are potentially precursors of volcanic eruptions. This particular type of caldera is a very explosive one. It's like Yellowstone. And there hasn't been one of those erupting in the US in historic times, but when they go, they're massive. They make Mount St. Helens look like a little fireworks display.

So that was the first heavy involvement. That was in the 70s or 80s sometime. That was the first time I can remember the Geological Survey really getting in and working with the Forest Service and the town of Mammoth Lakes to let them understand what the hazards were, what they needed to do, and so forth. And there was a lot of controversy. The people who rent out rooms and operate the ski hill at Mammoth Mountain didn't like to hear that they might be living in a hazardous place. But it turned out well in the end. In fact, one of the positive results was that the town and the Forest Service built an escape road that goes out of Mammoth Lakes to the north. Before that road was built there was only one way out of Mammoth Lakes, and it went right toward the caldera. Every other road was a dead end. So, they built an escape road that went out to the north and comes out somewhere around June Lake.

Zierler:

Now, for the Hawaiian Island research, did this involve any undersea exploration to collect samples

Dalrymple:

Well, just dredging and drilling. If you're thinking about a remote vehicle or something, no.

Zierler:

Is that because you don't have to go down that deep?

Dalrymple:

No, we were mostly in the tops of these volcanoes. I think the deepest one we drilled was a couple kilometers deep. But we didn't have any kind of a vehicle available to us, for one thing. The US Geological Survey operated a couple ships at the time, so we did have a couple ships we could use. And we could and did apply for use of the Glomar Challenger, the drilling vessel operated by the National Science Foundation. So, we never really considered a remote vehicle. We didn't have access to anything like that. And I'm not sure it would've helped. It's not a go down, look, and see sort of thing anyway.

Zierler:

Now, were you in touch with Wilson upon finding that his hypothesis in the hotspots was confirmed?

Dalrymple:

Oh, yeah. Virtually everyone you've heard of involved with plate tectonics used to be at all these meetings at the American Geophysical Union and sometimes the Geological Society of America and sometimes a smaller, informal meetings. So Tuzo was a frequent attendee at meetings large and small, and we got to know him pretty well. That was part of the fun. Every couple months there was a meeting, whether a large one or a small one, that someone had put together. And everybody who was interested in working on this problem would come. And so, you got to know all these people and share ideas with them. And it was pretty neat. But yeah, we were in touch with just about everybody.

Zierler:

What were some of the advances in the late 60s and early 70s in K-Ar dating, techniques and technology?

Dalrymple:

Well, I guess most of the advances after the Reynolds mass spectrometer came well after plate tectonics had happened. The first one was, instead of measuring potassium, you irradiate the samples in a reactor, and you get a fast neutron reaction that turns some of the potassium-39 into argon-39, so you can essentially measure the age just by measuring the ratios of the argon isotopes. It's a little more complicated than that, but we'll just leave it at that. That method is a lot more precise because you're not measuring two different elements or isotopes of two different elements. You're simply measuring isotopes of the same element, and that makes things a lot more precise. So that was the first breakthrough. That was a technique that had been proposed and explored at Berkeley before I got involved in it. The first one to actually use it was a graduate student in physics, Craig Merrihue, that I knew because he was at Berkeley when I was. Craig started using it as a technique for measuring the ages of meteorites.

That technique, referred to as the Ar-40/Ar-39 method, Or the 40-39 method, eventually got to the point where it looked to me like it would be a pretty good thing to use on rocks, too, instead of just meteorites. The Geological Survey had a one-megawatt TRIGA nuclear reactor in Denver that they were using for other things. So, I sat down and did all the calculations required to satisfy the NRC and our own needs. And we developed some equipment to be able to irradiate samples. My colleague, Marvin Lanphere, and I started exploring the 40-39 technique. And at that time, there was only one other lab in the country that was doing it and that was Jerry Wasserbergs lab at Caltech. So, we essentially explored that, explored its limits, what it was good for, what it wasn't good for. And that was a huge advancement in the isotope dating of rocks and minerals.

And then, the second big revolution was something that I borrowed from another colleague at University of Toronto, Derek York. Instead of melting rocks using an induction furnace and using big chunks of rock, measured usually in grams, Derek got the idea that maybe you could use a laser to melt little, tiny pieces. So, I went to Toronto and visited Derek, and he encouraged me to look into this. I went back and built a laser system, coupled with a brand new ultra-sensitive mass spectrometer, that would measure little, tiny samples. I was working on lunar samples that were 1/1000th of a gram.

Zierler:

What was valuable about working with such small samples with lasers?

Dalrymple:

Well, sometimes you can only get small samples. For example, the lunar samples. An important question of interest was the early impact history of the moon, a problem that I worked on with Graham Ryder, who was at the Lunar Science Institute in Houston. Graham was a specialist in melt rocks, which were the completely melted and recrystallized products of large impacts, and he could identify rocks that had been melted from rocks that were un-melted fragments that had just been blasted out by an impact. So, these rock fragments are all mixed up together. So, you don't want a piece of old rock, what you want is a piece that was formed during the impact that was completely melted. And Graham could pick these out. But we're talking about little, tiny samples, itty-bitty things you could barely see.

And so, with the laser system and a super sensitive mass spectrometer, we could actually measure the ages of these little melt rocks. My collaboration with Graham came about when I was at a lunar science conference and heard Graham talking about these melt rocks. He was bemoaning the fact that he didn't know the ages of these things, so he couldn't tell much about the impact history other than just relative speculation. So, I went up to him after his paper and said, "I think we can measure the age of those things. Why don't you send me a few samples?" So that turned into a long research project that actually wasn't finished until after I retired from Oregon State.

Zierler:

When did you first connect with Glen Izett?

Dalrymple:

Glen worked for the Geological Survey in Denver. And I don't remember when I first met Glen, but it was a long, long time ago, fairly early in my career. And we weren't working on anything in common, so it wasn't a colleague relationship right away. But eventually, it turned into that. Glen and I worked on some tektites from the Chicxulub impact crater. And then later on, Glen used to come and use the laser lab. I taught him how to use the laser system. He and John Obradovich, another colleague of ours in Denver, would come and just use the lab for their own purposes.

Zierler:

When was it considered that this meteorite impact was what actually killed off the dinosaurs? Was this before or after you got involved in the research?

Dalrymple:

I got involved shortly after the Alvarezes proposed this. Because these tektites were found in Haiti, and Glen got his hands on some of these things and proposed that we measure their ages. So, there were a lot of things happening simultaneously. A lot of people got interested in it. But there were two questions. One, was there a meteorite impact? And the answer to that turned out to be yes, from lots of lines of evidence. But those little tektites were one of the first lines of evidence that said yes, there was a meteorite impact, and it happened 62-63 million years ago. The second question was, did that impact kill off the dinosaurs? That's an entirely different question, and that's out of my field. [laugh]

Zierler:

What's the relevance of dating the tektites in regard to whether or not there was a meteor impact? When you look at the site, doesn't the site tell you itself that there was a meteor impact?

Dalrymple:

Well, remember that the Chichulub crater is now buried so the idea of an impact at the Cretaceous-Tertiary boundary came well before the location of the crater was known. The Alvarezes hypothesized the impact because of a very thin layer in a sedimentary sequence in Italy. And they were trying to explain what that thin black layer was. It was only a little, thin thing. And they sampled it and found it was very high in some of the platinum group metals, particularly iridium. That little layer was hypothesized to be a deposit from a meteorite impact. And then, the tektites were found in Haiti, and those are usually a result of meteorite impacts. Essentially, tektites are glass that has been melted and splashed out. But that little thin later turned from this impact was right at the Cretaceous-Tertiary boundary. And of course, the cretaceous was the age of the dinosaurs and that layer was right where the dinosaurs disappeared. So that seemed like a really huge coincidence.

Zierler:

How did you get involved in the Apollo 15 and Apollo 17 impact melt rock research?

Dalrymple:

Well, I mentioned that the melt rock project was a result of a paper I heard that Graham Ryder presented at a lunar science meeting. And I was at that meeting because during the early days, before the moon rocks were sent back, NASA was scrambling to get as many proposals as they could to measure things. They didn't care what you measured. They wanted every possible measurement to be made on these lunar samples that they thought were going to be brought back. And so, it was really easy if you had something that was different at that time to get some money from NASA and get in line to get some moon rocks. So, Richard Doell put in a proposal to measure magnetism on these rocks in the lab when they first came back. And he actually developed a piece of equipment to do that.

And then, he and I put in a proposal to measure thermoluminescence in the lunar samples. We were trying to use thermoluminescence to date really young volcanic rocks. And it turned out that’s not a very good technique for our purposes. But we put in a proposal and were encouraged by NASA to do this to measure thermoluminescence on the lunar rocks. And there were several other groups working on this, too. So, I became a principal investigator as the result of a sort of a lark. "OK, you want me to measure thermoluminescence? I'll do that. Give me some money." So that essentially got me into the business with lunar rocks.

So, I was a PI for Apollo 11 and 12. Apollo 13 didn't get to the Moon. And then, I just dropped out of that because I didn't think the thermoluminescence work was worth doing. It had a bit of relevance about the churning of the lunar soil, but essentially I thought it was a waste of money. Nevertheless, I kept going to lunar science conferences, and I heard Graham Ryder give this talk about melt rocks from these huge impacts that created the lunar basins, and I approached him on that and told him I thought we could provide some age data for what he was interested in.

Zierler:

What were the results of the findings?

Dalrymple:

Well, we never found any melt rocks older than about 3.9 billion years. And when these impacts happened, most of the debris, about two-thirds of it, gets thrown out as just fragments. Their isotopic clocks have not been reset. So, it looked to Graham and me that if there'd been a continuous lunar bombardment starting from when the lunar crust first formed, and there was a climax around 3.8 billion, there should be older melt rocks around as well. And we never did find any. We looked at every single return lunar mission, and we couldn't find anything older than about 3.9 billion years old. So, it looked to us like it wasn't a continuous lunar bombardment with a cataclysmic end, as was the popular hypothesis of the time, it was just the cataclysmic end that happened. That is, once the moon was formed, then it was fairly quiet in terms of impact history. And there was this huge bunch of large impacts right around 3.8 to 3.9 billion years.

Zierler:

What were some of your motivations in becoming something of a public figure in this broader societal debate between creationists and science?

Dalrymple:

I got into that issue primarily because of Garniss Curtis. The California attorney general had called Garniss to see if he would be an expert witness in the Seagraves vs California Board of Education trial. The Seagraves were suing the Board of Education for teaching evolution in the public schools because they didn't believe in that stuff, and they didn't think their kid should have to take it. So, the attorney general called Garniss and asked if he would testify. And Garniss was busy, going to be gone or something. So, he told the AG, "Why don't you contact my former graduate student?" I had been at the Geological Survey for a number of years by then. So, the AG’s office called me, and I agreed to appear in that trial, which fizzled. Essentially, there was no trial because the Seagraves agreed to a minor change in wording in the Board’s biology curriculum, which essentially changed nothing. But the preparation for the trial got me interested in the whole creationism thing and understanding that the creationists were trying to get religion taught in science classes in the public schools.

Zierler:

Was your expert role in this specifically on the age of the Earth or on evolution, which would, I assume, be more of a biological component to expertise?

Dalrymple:

It was on the age of the Earth and the long history of the Earth, including the ages of events in earth's history as well. The connection is that evolution requires considerable time and if the Earth is very young, say only 6,000-10,000 years old as the creationists erroneously insist, then there is not enough time for the evolution we see to have taken place.

Zierler:

And so, to the extent that you tried to understand their viewpoint, is the age of the Earth that we measure in billions of years antithetical to a religious point of view?

Dalrymple:

Well, for this small group of people, it is. They're hung up on estimates that are essentially Bishop Ussher-type calculations that they don't do themselves. But they think the earth is only 6,000 to 10,000 years old. They don't have any evidence for that so they deny not only evolution, but the age of the Earth as measured by science, because evolution requires a long period of time. Therefore, if the earth is only 6,000 years old, there's not enough time for evolution to happen.

Zierler:

I wonder what you learned from this experience about the broader role of a scientist in society.

Dalrymple:

Well, I think it's fairly important. I mentioned talking to the California committee on bay fill about earthquakes. That was sort of my first involvement in trying to make science relevant to a problem. And the same thing with education. I think probably all of us have something to contribute if we are just willing to take the time to do it. I think education is pretty important. And my feeling is that if people want to teach their kids that the earth is 6,000 years old, have at it, but not in the public schools because that view is scientifically wrong.

Zierler:

Were you thinking more broadly about The Age of the Earth having nothing to do with this political work? Or was it really the political work that motivated you to write these books?

Dalrymple:

It was the latter. It was the testimony from trials, the depositions I gave. And then, I got involved in writing articles about this and giving public lectures. All of this involvement I found very instructive and a lot of fun because I met people I never would've met otherwise. Who would've thought I'd be hobnobbing with theologians, for crying out loud? But I've never done any research on the age of the Earth. I've never made a measurement that was relevant to the ultimate Age of the Earth. But in gathering information for these trials, it soon became pretty apparent that there were no good, comprehensive books on the subject. There were a couple of short ones, but the last comprehensive book was in the 1930s. It was a National Research Council volume edited by Arthur Holmes. So, I decided I’d write one. I started out to write a short one for non-scientists, but I got really interested in the subject, and the book turned out to be a long one of about 450 pages. Later I went back and wrote a shorter version.

Zierler:

What needed to be updated from the literature in the 1930s? In other words, in the 1930s, was the going assumption that we're still operating in the five, six-billion-year range?

Dalrymple:

No, in the 1930s, there were lots of estimates, but they tended to be hand-waving estimates. Billions of years. Or there were a whole bunch of questionable calculations that tended to be in the tens to hundreds of millions of years. The age of the Earth wasn't really known until the mid-1950s. That was when Clair Patterson, at Caltech, published the first paper that used lead isotopes to measure the ages of meteorites, which represent the time of formation of the Solar System and, therefore, the Earth. Patterson’s result of 4.55 billion years has been refined and the evidence strengthened but has not change in any major way.

Zierler:

What were the advances that made that finding possible?

Dalrymple:

The first age of the Earth, published by Patterson, was done on the basis of lead isotopes. So, it required a couple of things. It required the availability of equipment and techniques to measure lead isotopes precisely, so he and others could measure lead isotopes in meteorites. And the second thing was the ability to make an important correction. One always has to correct for the amount of the daughter product that's in the rock or mineral when it formed. So, you have a radioactive isotope that's turning into daughter isotope, say, uranium to lead, for example. And if you know it's just uranium and lead, you can calculate the age just based on those isotopes. But whenever a rock forms, there's always some lead initially there.

So, you have to be able to subtract that out. There are various ways to do this. But that's the tricky part. One of the things that Patterson used was the meteorite named Canyon Diablo, which is the meteorite that formed Meteor Crater in Arizona. That meteorite is named Canyon Diablo because the first fragments were found at Canyon Diablo, not at the meteorite impact site, but a little ways away. That particular meteorite has an iron sulfide phase in it that's called troilite. And that troilite has absolutely no uranium in it. Zero. Or as close to zero as they can measure.

And so, the troilite in Canyon Diablo has preserved the lead isotope ratio that existed when the Solar System formed. And that's what you need to be sure that you're correcting for the amount of lead isotopes that was originally there. So, Clair Patterson measured lead isotopes in meteorites, he had Canyon Diablo, which fell right exactly on the same line, an isochron, and that line told him the age of the Earth. 4.55 billion was the result of his calculation. And since he first did that in the 1950s, the number hasn't changed that much.

Zierler:

And to what extent is this research dependent on even bigger questions, such as the age of stars, or galaxies, or even the universe itself?

Dalrymple:

Well, it's all kind of tied together. Astrophysics got in the embarrassing situation a few years ago, where it looked like some stars and galaxies were older than the age of the universe. Of course, that was just caused by errors in the measurements. But you have to have consistency amongst all these measurements. If we had a solar system, for example, that, based on meteorites, was measured to be, say 50 billion years old, that would not work very well because the universe is probably only a little less than 14 billion years old. So other than the consistency, that's about it. You're really looking at a history of the universe, and the ages of Earth and the Solar System look like they fall in a reasonable timeframe.

Zierler:

Now, were you looking to reach a popular audience? Was this for undergraduates? Who was the intended demographic?

Dalrymple:

Well, the first one turned out to be a rather thick book. It's 451 pages long. And people have asked me who I wrote it for, and I say, "I wrote it for me." It's something that might be on a geologist's or physicist's bookshelf and perhaps used as a reference in a class. Then, I tried to popularize it in a smaller book, and I think I did a pretty good job. But what I eventually realized is, there's no such thing as a popular audience for these kinds of books. You're either a science enthusiast, or you're not. And there are a lot of people who are science enthusiasts but aren't scientists, and they read these books written for non-scientists. But the average person could care less. Anyway, it was a challenge to try to write one that anyone could understand if they really wanted to put some work into it.

Zierler:

Tell me about your tenure as president of the Geophysical Union.

Dalrymple:

That started as kind of a fluke. It was never my goal to be an officer of a scientific society. At the time, I was the Assistant Chief Geologist for the USGS’s Western Region, headquartered in Menlo Park, and one of my colleagues, Jim O'Neil, an oxygen isotope guy, came running in one afternoon and said, "You've got to help me." I said, "What's the problem, Jim?" Well, it turned out that Jim had been tasked with nominating two people to run for the president of the Vulcanology, Geochemistry, and Petrology section of the American Geophysical Union. He had nominated two people. Irving Friedman was one, and the Heinrich Holland was the second.

Heinrich was a well-known geochemist from Harvard. Jim told me, "I nominated these two people to run for president of the VGP section. Irving just called me and told me he would not run against his good friend Heinrich, and I need another nominee within an hour. Will you run?" I said, "OK, I'll be your sacrificial lamb." [laugh] So I ran, and I won. And then, of course, you're in that position on the council for four years, first as a section President-Elect and then President, and near the end of my term I was nominated for the president of AGU, which was quite an honor.

Zierler:

What were some of the most pressing issues you had to deal with as president of the AGU?

Dalrymple:

Electronic publishing was just starting to come into being then, and that was a big issue. Eventually, it got sorted out. But most scientific societies, including the American Institute of Physics, are essentially publishing companies. That’s where most of their income comes from. It comes from selling journal subscriptions. So, the impact of electronic publishing was going to be huge. The problem involved how to generate income from this new publishing method, stay in business and continue to serve the community. So that was probably the biggest issue at the time I was president. The other one was different. I'll go back a little bit. My good friend and colleague Allan Cox was AGU president several cycles before I was. At the time Allan was president, the AGU was housed in various government buildings around downtown DC. So, when Allan was president, he engineered the purchase of a building, at their current location of 2000 Florida Avenue in Washington DC, not too far off the Dupont Circle. Allan took great pride in the fact that he had bought a building for AGU while president. He considered that one of his major accomplishments, and it was.

And my great pride when I was AGU president was that I tore it down. Actually, they tore down the existing building and built a new one in its place. So that was another big issue in addition to electronic publishing. "The building needs a lot of repair. Do we tear it down? Do we build a new one? Do we go buy another one someplace else?"

Zierler:

And then, relatedly, how did you get involved with the Board of Governor Leadership position at AIP?

Dalrymple:

It was directly related. The president-elect and president of AGU, as well as the officers of the other scientific societies that are members of AIP, were, at that time, automatically on the board of AIP. Whether or not that’s still true I don’t know.

Zierler:

And so, what were some of the major issues at AIP during the 90s that you dealt with?

Dalrymple:

Again, the biggest one was electronic publishing because a primary function of AIP, like AGU, is publishing scientific journals.

Zierler:

On the education side, did you always have graduate students?

Dalrymple:

I had graduate students at the USGS, most of them from Stanford, but I had some from the University of Hawaii, San Jose State, and one from Japan.

Zierler:

And so, they would come to you as part of their thesis research, or mostly as post-docs?

Dalrymple:

Occasional post-docs. But they came to use the laboratory. And I was always supportive of students to the extent we had capacity. Stanford had no isotope facilities at the time. None whatsoever. So, if they had a student who got interested in dating rocks, or using isotopes, or some other reason, they had to come over to the US Geological Survey. And mostly, they were welcomed.

Zierler:

Did you have the opportunity to teach at all at Stanford?

Dalrymple:

I taught a couple of classes.

Zierler:

What kinds of classes did you teach?

Dalrymple:

Isotope geology, different dating technologies.

Zierler:

I'm curious if you had a sense that, by the early 1990s, your work on geomagnetic reversals was really going to be recognized by the community with your election to, for example, the National Academy.

Dalrymple:

Elections to academies and awards like medals are funny things. Number one, there aren't enough of them to go around. There are always more good people who deserve them than ultimately get them. And number two, they tend not to give them to young people because they think you might be a flash in the pan. Besides, there are all these old people waiting. So, Allan and Richard were elected to the National Academy fairly early on, right after the reversal time scale and its importance to plate tectonics was known. And they were also awarded the Vetlesen Prize, which was a big deal. And it may be the only citation in Vetlesen Prize history that names a person who isn't given the prize. I was worked into the citation, but not the prize itself. So, I found that kind of interesting. And then, in 1993, many years later, I was elected to the Academy. And then, in 2005, I was given the 2003 National Medal of Science. And both of those things primarily cited the reversal work, which was done decades before. So, I’ve always thought that was kind of amusing.

Zierler:

Why such a long gestation period? Any idea?

Dalrymple:

Well, I think when it comes to awards, there are lots of perfectly deserving old folks lined up for them. Some young guy didn't get the 2003 National Medal of Science because I did. And by that time, I was an old guy. By the time I was awarded that medal, I was retired, not doing anything useful, and they were citing things I'd done 40 years before. I find that kind of funny. The other thing is, it's just the odds. The Geology Section of the National Academy of Sciences gets two to three people elected a year. And there are a lot of more deserving scientists than that. Geophysics gets another three or four, but that includes solar physicists and other kinds of geophysicists as well. So, in terms of earth scientists, there just aren't that many slots available and deserving people get left out. Similarly, with the National Medal of Science. For 2003, the medal was awarded to seven of us who were selected from a nomination list of hundreds, so a lot of luck is involved.

Zierler:

What were the considerations in retiring from the Survey and going to Oregon State?

Dalrymple:

I'd worked for the USGS, the federal government, for 31 years and I was kind of losing my sense of humor. The Survey was going through a rough patch at the time. And I just decided, "Been there, done that." Time to see what else was available. One of the things that happens when you're elected to the National Academy of Science is that you get job offers because universities want to collect you. So as soon as I was elected, I had a number of job opportunities, and I decided to take advantage of what looked to me like a good one. And it turned out to be a very good move for me.

Zierler:

What was your role there? What did you do as dean?

Dalrymple:

Try to stay out of the faculty's way and help them get research money.

Zierler:

Did you see this as an opportunity to do your own research? Or this was more administrative?

Dalrymple:

It was entirely administrative. The College of Oceanic and Atmospheric Sciences, which it was when I was there--it's now Earth, Oceanic, and Atmospheric Sciences because they incorporated the geology and geography departments into it after I retired--is one of the largest and best-known oceanographic institutes in the world. It's probably in the top four. And so being dean is mostly an administrative job. Virtually any college dean is considered a full-time administrative job.

Zierler:

What were some of the big projects going on at the college at that point?

Dalrymple:

Oh, my. That's a hard one to answer. We had people involved in ocean drilling, people studying thermal balance in the oceans, people studying how beaches form. I don't know that I can name any one big one because there were a bunch of them. And the research projects were all essentially faculty driven.

Zierler:

Was there any learning curve for you, coming from geology into oceanography?

Dalrymple:

Oh, yeah. That was the fun part.

Zierler:

In what ways are the fields related, and in what ways are they totally different?

Dalrymple:

Well, oceanography in general is like geology in the sense that what you're doing is applying the basic sciences, physics, chemistry, biology, to the study of the oceans and the ocean floors. And geology's the same way. As I mentioned to you, we've got some theories, like the youngest rocks are on top. But by and large, we're using physics and chemistry to study the Earth. So, it's very similar in that way. But yeah, it was lots of fun learning about ocean currents and things that I knew nothing about. One of the things I used to do was have my assistant make appointments with the faculty, and I'd spend half an hour or an hour with them, have them tell me what they're doing in simple language, so I could understand it. Sometimes people asked me what I taught when I came to Oregon State, and I always reply, "I didn't know enough to teach, so they made me a dean."

Zierler:

[laugh] Did you take this knowing that it would be a relatively short tenure at six years, that you would be retiring roughly in that range?

Dalrymple:

Yeah, I intended to follow Charlie Anderson's advice. I was going to retire at 65 or before. Actually, I was 64 when I retired.

Zierler:

Where were you when you got the call that you were about to receive the National Medal for Science, and who was on the other end of the phone?

Dalrymple:

It was a person from the National Science Foundation who was frantic. And the reason she was frantic was because Sharon and I, until this year, had a condominium over in Bend, Oregon. We used to go over there and spend a week at a time. And we had gone to Bend. I was retired so I didn't tell anyone at the university where I was going, like I used to have to do. So, they were trying to contact me, and nobody knew where I was. The problem was, they couldn't announce the recipients publicly until all of them had been notified, so I was holding up the works. So, when we got back from Bend, I had this frantic message on the phone to call Washington. The medal was a total surprise.

Zierler:

What was the timeframe? How fast did you have to get to Washington?

Dalrymple:

I don't remember exactly, a month or two.

Zierler:

Were there any protocols or dealings with the Secret Service in preparation for meeting the president?

Dalrymple:

Well, if you read my biography, you'll notice that I got the 2003 medal in 2005. The FBI investigates every recipient. The reason is that they don't want the White House to be embarrassed because they're giving a medal to a child molester, or bank robber, or some other form of monster. In 2003 the FBI was very busy with investigating terrorists so the FBI just didn't get around to it for a couple of years. And then everyone who attended the ceremony in the White House had to be cleared by the Secret Service as well. Interesting enough, there hasn't been a medal given since 2016.

Zierler:

I'll come back to that, but first, tell me about the day. Where is the medal conferred?

Dalrymple:

In the White House, the East Room. The operation is generally run by the National Medals Foundation. They do the National Medal of Science and National Medal of Technology, which are presented at the same time. And the rules require anywhere from 0 to 20. Mostly, it's six, seven, something like that, of each. So, we had a reception at the National Academy of Sciences, that was kind of neat. And then, after the medals are presented, there's a huge banquet with, like, 400 people, which was fun, too. But the ceremony itself was at the White House. And we're supposed to be allowed two guests, and I informed them that I had three daughters, a wife, and one son-in-law who were eager to be there. And they made allowances, so they all got to come. But it's really a well-done ceremony. We got to meet with President Bush for 20, 30 minutes before the ceremony, and then again afterwards. And he was an interesting guy. He seemed to have no intellectual curiosity at all. He said, "How are ya," and, "Welcome to the White House." But I think in our case, there were, like, seven National Medal of Science medalists and another six or seven National Technology medalists. And you'd think that anyone who was curious would be asking these people, who he had captive, a few questions. And I can't imagine Obama, Clinton, or someone asking any questions. But George Bush didn't ask anyone any questions.

Zierler:

Do you have an idea of the nomination process, who was championing your research from decades earlier?

Dalrymple:

I do. It was a guy by the name of Marcus Milling, who I actually didn't know well at all. I think I may have met him a time or two. But he was the executive director of the American Geological Institute, which I think is now the American Geosciences Institute. He called me one day and told me what he wanted to do. And I said, "You're wasting your time. Why don't you spend it on someone who's more likely to get it than I am?" And he said, "No, I really want to do this. And I want to send you nomination papers and let you check it over, make sure I haven't made any mistakes." I said, "OK, but I warned you." So, he sent it to me, and I made a few minor corrections. Then, I totally forgot about it. That was several years before. When I actually got the medal, it was a complete surprise. I was informed later that they get roughly 400 nominations a year, and then they carry over 200 from one year to the next. So, you're looking at a huge pool of people. I'm surprised they get that many nominations because making a nomination's tough. If you've ever done it yourself, it's a hard thing to do. But yeah, it just defied the odds for me to get that medal.

Zierler:

Going into retirement, did you have a really good sense of the kinds of things that you wanted to do in your spare time? Or did you play it out in real time in the new hobbies you would take on?

Dalrymple:

Oh, no, I've always been interested in things like woodworking and athletic things like skiing and golf. So, I knew I was not going to have any trouble filling up my time. That wasn't an issue. I've known people in the past who have retired and gone to tend their gardens, and they usually die in about six months. I wasn't going to do that.

Zierler:

And for you, it was all kinds of things.

Dalrymple:

It was all kinds of things. I had trouble limiting what I wanted to do. My wife and I used to travel to do adventurous things. We both are certified scuba divers, and we used to have a lot of fun doing that. We dove the Great Barrier Reef in Australia, places in the Florida Keys, Hawaii. We've been to the Galapagos Islands and been on a number of cruises where you can see all kinds of wild animals. Been to Africa. So, I never had any trouble filling up my time with interesting things to do.

Zierler:

If we can start to think about a post-pandemic future, what are you most looking forward to doing that you haven't been able to do in this past year and a half?

Dalrymple:

Visit our kids. Or have them come here. One of our daughters is living in Hawaii temporarily, has been for the last year, and the other two are on the East Coast. In a way, that's been fortunate because if they'd been right down the street or in the next town, we'd have been tempted to break our confinement and visit them. And that probably wouldn't have been a good thing to do. But we've been essentially isolated from our daughters and their families by long distances. But yeah, I miss seeing the kids. And Sharon and I used to go to Hawaii for a couple weeks every year. We miss doing that, too.

Zierler:

Now that we've worked up to the present, for the last part of our talk, I'd like to ask a few broadly retrospective questions about your career. And the first is, since you started thinking about geology, for your own research and in the field more general, what was not understood at a given point in time, and at least since you stayed current in the field, up to the end of the 20th century, what was understood as a result of both your research and the research of your colleagues?

Dalrymple:

I mentioned continental drift. That's certainly one. We understand that continents do move around, we know generally how they move around. I think the forces are less clear, but clearly, convection in the mantle has something to do with it. But when I was in school and the earliest part of my career, we simply did not know how the earth worked. We didn't know how continents moved, we didn't know why mountain ranges were where they are, we didn't know why volcanoes were where they are. And there were all these hypotheses, and looking back on them, some were just nutso. I had to learn, as a graduate student, 32 or 33 different kinds of geosynclines, which were supposed to explain sedimentary basins. Well, we all now know that's hooey. Now, we know it. Then we didn't. As I mentioned, we didn't know why the Appalachians were where they were, why the Rockies were where they were, why the San Andreas Fault was where it was and what it did.

And so, it was like living through a revolution in biology with the discovery of DNA or the revolution in physics around the turn of the last century, when they discovered the structure of the atom. Plate tectonics was that big a deal. It’s really the first theory of how the Earth works. It's the sort of revolution that comes along in a science maybe once a century, if that. And it just changed absolutely everything. It was interesting to watch scientists respond. Some were skeptical. There were a few holdouts until the last. Took about three or four years, and then they just died off. But most of the people I knew who were studying whatever they were studying all of a sudden saw how their study fit into this bigger picture of how the earth worked, and it started to make some sense.

Zierler:

To what extent does the revolution on plate tectonics give us a sense of how to extrapolate? In other words, where the continents will go into the future.

Dalrymple:

Well, they can measure that. They can measure the direction of the continents. They're moving now. So, they know how fast the sea floor is spreading. They can't predict when there's going to be a shift in direction. Because when you change one thing, if you somehow force one continent or plate to move in a different direction, all the other plates have to adjust. So, I don't think they can make that prediction, but they can certainly measure the current directions and velocities.

Zierler:

To flip that question around, what mysteries remain in the field, things that were questioned even 50, 60 years ago, for which there are still no good answers?

Dalrymple:

Well, this is a field I haven't kept up with very much, but from what I understand, I'm not sure they really understand how the earth's magnetic field is generated and how and why reversals occur. Last I knew, the reversal mechanism was a minor part of the energetics of the entire field. But I'm not sure that's solid. I don't know that the driving forces of plate tectonics are completely known, other than vaguely saying it's driven by convection. For the Hawaiian Islands, some talk about plumes of material coming up from maybe the mantle-core interface. But as far as I know, there's no evidence of that other than the islands themselves. But where that hot rock is ultimately coming from, I don't think anybody knows for sure.

Zierler:

For my last question, I'd like to ask, of all the research that you've been involved with, all the collaborations, what's been most intellectually satisfying for you?

Dalrymple:

Our reversal time scale was part of it, but I think the work I did in researching for my books on the age of the earth. That was probably one of the few times I dove into a subject that thoroughly. I dove into nuclear physics enough to be able to calculate nuclear reactions in a reactor because it was necessary for my research, but in the age of the earth, I had to essentially dive into everything that applied to that, including the ages of galaxies, stars, and the universe. So, in terms of intellectual satisfaction, to me, it's learning something. So, I think that was the most satisfying thing I've done.

Zierler:

Not only learning for yourself, but learning for all the people who have enjoyed your books.

Dalrymple:

Yeah, maybe. [laugh] All six of them.

Zierler:

Brent, it's been a great pleasure spending this time with you. I want to thank you so much for doing this.

Dalrymple:

Well, it's been my pleasure, David.