Susan Kieffer (PhD '71), Geologist

Understanding the nature of volcanoes and geysers, both here on planet Earth and elsewhere in our solar system, requires mastery of the underlying physics—specifically fluid dynamics and thermodynamics. In Sue Kieffer's long and varied research career, she has mixed theory, observation, and field work to contribute fundamentally to our understanding of any kind of geological condition that is hot, and/or, flows.

Kieffer completed her PhD on shock waves and meteorite impacts at Caltech in 1971, and she has held faculty appointments at UCLA, the Arizona State University, the University of British Columbia, the University of Illinois, and a research appointment at the United States Geological Survey. Her numerous honors include election to the National Academy of Sciences, a MacArthur Fellowship, the Penrose Medal from the Geological Society of America, and Caltech's Distinguished Alumni Award.

Keen on science communication and conveying her findings to a broader audience, Kieffer is the author of The Dynamics of Disaster, which surveys natural disasters from the perspective of fundamental science.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, November 19th, 2021. It is my great pleasure to be here with Professor Susan Kieffer. Sue, it's great to be with you. Thank you so much for joining me.

SUSAN KIEFFER: Thank you for the invitation.

ZIERLER: To start, would you please tell me your current or most recent title and institutional affiliation?

KIEFFER: I am Emeritus Charles R. Walgreen Jr. Professor of Geology and Emeritus Center for Advanced Study Professor of Geology at the University of Illinois at Urbana-Champaign (UIUC).

ZIERLER: Who was or is Charles Walgreen, Jr. and is there any connection between Walgreen and your research?

KIEFFER: Charles R. Walgreen Jr. (1908-2007) was the son of the founder of Walgreens Corporation. The Walgreen Corporation is based in Deerfield, Illinois, and Mr. Walgreen Jr. endowed Chairs at the University of Illinois and the University of Michigan. The endowed Chairs at UIUC were specifically to recruit high-level senior people, and they have no direct connection to the topics of research of those people.

I was living in Canada when two Walgreen Chairs became available to the University of Illinois. I loved being in Canada and, in fact, am now a dual citizen, but I'm a planetary scientist and the Canadians don't have the kind of planetary science program that the U.S. does. I was getting increasingly isolated from any productive work by ~2000 and I happened to mention to an American geologist friend that I was thinking about trying to come back to the U.S. He went through grad school at UIUC with the man who was the Dean of Liberal Arts and Sciences at UIUC when I was pondering returning to the U.S. This discussion was happening just when the Walgreen Chairs came to UIUC, and the Dean came up with this wonderful, endowed Chair. That Chair paid for part of my salary and gave me $30,000 a year to fund anything except my own salary. The connection of the Chair to my research is that I supported my postdocs and grad students to a certain extent from those funds.

ZIERLER: Another part of your affiliation you mentioned – Center for Advanced Study Professor. What is the Center for Advanced Study?

KIEFFER: It's both a physical center and an intellectual center at UIUC where professors and others on campus can meet occasionally to discuss interdisciplinary ideas. It really serves the purpose of trying to fund professors, especially young professors, for release time to pursue research and other professional activities, and to offer a wide variety of events to connect the University with the general public.

ZIERLER: But it's multidisciplinary? It's not just scientists?

KIEFFER: That's right. Unfortunately, when I was there, the CAS Professors didn't meet all that often. It wasn't like you could go there and have a weekly lunch with two dozen other people. It was small and located in an old house near the Urbana campus. I haven't been back to Illinois for a couple years because of the pandemic, but I believe that they have now moved to a better facility.

ZIERLER: It's coming up on ten years since you've gone emeritus. What have you been doing? What is interesting to you in your research life in the past decade or so?

KIEFFER: I went emeritus a little early in 2010 because I got married in 2008 and I wanted to have more time to live my personal life without feeling guilty about the traveling that we love to do. I loved being at the University of Illinois but I really wasn't happy living in the Midwest, and so when I retired I could move to the west coast where I've always felt more at home. I've had several projects since then. One of them occupied much the last two years. There is a strange little volcano, Volcán Bárcena, on an island west of Mexico. It has some very unusual linear grooves going down its flanks that do not look like patterns formed by rain. I worked with a colleague at the University of Santa Barbara, a colleague at Illinois, and Joanna Austin at Caltech in Aeronautics. We came up with an explanation that these features were formed by vortices—longitudinal vortices aligned in the direction of the flow and existing in the boundary layer at the base of the flow. We worked out some properties of the flow by inverting the properties of the grooves to properties of the boundary layer. It took a long time. I usually haven't had to spend two years on what turned out to be a fairly simply concept.

Now, I'm working on some data—and this is a long story that connects back to Caltech. When I was at UCLA as an assistant professor after I graduated from Caltech, I realized that I wanted to study volcanoes but I had never done any research on volcanoes. I decided that geysers might be an analog for volcanoes and that maybe I could at least understand a system that was just simple boiling water. That was in the mid-1970s and almost 50 years later, I'm still working—I've got, right here on my desk—on my 1984 data from Old Faithful.

I did my Ph.D. thesis work on the effects of shock waves on the rocks when a meteorite hit in Arizona and formed Meteor Crater, near Flagstaff. Although rocks are generally incompressible, meteorite impacts generate such strong pressures that the rocks are very compressible and act like fluids. The only place at Caltech to learn compressible fluid dynamics was in the aeronautics department, and I either took, or audited, compressible fluid mechanics from Brad Sturtevant. After Mount St. Helens erupted in 1980, Brad got interested in the ideas that I had proposed for the eruption dynamics and we started collaborating. One of the great things that happened when I was visiting there to work with Brad occurred when I was sitting outside eating lunch on a bench by the Millikan pond. Jim Westphal, a professor of planetary science came by, sat down and we got talking. Out of that grew the idea to put two probes into Old Faithful. The first one was a pressure-temperature sensor probe, and the second one, more than ten years later, was a miniature TV camera. That was a real challenge but Jim was a brilliant experimentalist. We rigged up this little camera that had to be encased in ice, because we were lowering it into steam and had to have its own illumination system because the conduit is dark. We took videos of the properties of the conduit. Jim put together a lovely little 16-minute-long video that has become quite popular-"A Short Voyage Towards the Center of the Earth." One piece of it was actually used in an IMAX film about Yellowstone! That was a really productive time, and I was really glad to be able to come back and interact with colleagues as a professional geologist rather than as a grad student.

ZIERLER: Between your academic affiliations, your degrees, and the larger community of researchers that you're involved in, there's geophysics, planetary science, and geology. When do you wear any one of those specific hats for the research that's most interesting to you?

A Random Walk in Research

KIEFFER: I don't think of them as separate hats, I guess. My career has been basically a random walk, and professionally, my research was determined pretty much by events that kept happening in our Solar System. I started studying Old Faithful geyser as a volcanic analog in 1976, and before I got to think about applying the concepts to volcanoes on Earth, the Voyager 1 team discovered volcanoes erupting on Io, a satellite of Jupiter, in 1979. Gene Shoemaker, who knew of my idea that Old Faithful Geyser could be a volcanic analog, came to me and said, "Sue, could you apply your geyser theory to these volcanoes on Io?" The problem was those volcanoes weren't erupting water; they were erupting sulfur and sulfur dioxide. So that became a diversion in 1979. Then, a decade later, the next diversion was the discovery of geysers erupting on Triton, a satellite of Neptune. Those were cold nitrogen geysers, so then I got into modeling eruptions driven by nitrogen. Then the most recent diversion was the discovery of geysers on Enceladus, a satellite of Saturn in 2006. I had no control over those eruptions happening or their discovery, but I happened to be lucky enough to get to work on them.

ZIERLER: In your research that has relevance both for Earth and other planets, just from your perspective, is it possible to treat Earth just like any other planet and extrapolate those findings, or by virtue of this being our home, that's simply not possible?

KIEFFER: From the physical sciences side, yes, Earth is just one of many planets. I think that's the advantage of being a planetary scientist, because each of those problems I worked on made me think differently about the Earth. But Earth has life, and that's a huge component of being on this planet that is not common on the other planets. So it's a mixed answer.

ZIERLER: Of all of your interests in rare geological events, what should we be preparing for now? What might be of concern that is going on in the world?

KIEFFER: I guess I can say it ISN'T the big Yellowstone eruption.

ZIERLER: You think that's overblown?

KIEFFER: The 600,000-year event—well, I haven't worked on that specifically, but the people who do work on it professionally think that the next event is likely to be a basalt or hydrothermal (water driven) eruption, not another big caldera eruption. My bigger concern is the planetary resources and the availability and fairness of use of those resources given the huge population of the planet. There are more than seven and a half billion people here. I think that's the area where there's a big challenge ahead.

ZIERLER: Do you see your work in rare geological events as contributing to studies of how old the Earth is and how life formed on Earth?

KIEFFER: I think it does even though I'm not actively involved in the astrobiology aspects. I was just looking at a new work yesterday where some Canadian scientists are working on meteorite impact craters as potential sites for evolution of life because some of those big craters have hot water systems, geothermal systems, circulating in them. Those, over the past couple decades, have been recognized as being very hospitable to certain life forms.

ZIERLER: How have the advances in computational power over the decades been useful for your research?

KIEFFER: The big computational advances in my field started in about the 1970s. That was just before the time that I got involved with the 1980 eruption of Mount St. Helens. After that eruption, I started working on volcanic eruption simulations with some scientists at Los Alamos using Cray computers. I subsequently made a decision that I personally didn't want to get into the big computer codes. That decision was partly prompted by a near-miss in my scientific career. I wrote a paper on volcanism on Mars using a Los Alamos computer code that simulated volcanic eruptions as "black box code" where I just changed input parameters, but didn't actually look much at the code itself because it had been thoroughly debugged by LANL (for terrestrial eruptions!). In the input I changed the acceleration of gravity from being Earth's value to the gravity of Mars, which is about a third of Earth's gravity. I ran the code, and the results looked amazingly like volcanic eruptions on Earth—the same kind of gas behavior, the same plume heights for given input conditions. I rationalized this to myself by thinking that the fallback from an eruption of a Mars volcano had created a near-vent atmospheric pressure about equal to the vent pressure which I had taken to be 1 bar. The paper went through review for Science and one of the most prominent volcanologists at the time reviewed the paper and approved it. Somewhere in that last stage of manuscript, I discovered that there was a subroutine in this Cray computer code that reset the input Mars gravity back to Earth's gravity! That was why all my Martian volcanoes looked like terrestrial volcanoes! And that was the last time I used a black box computer code [laughs].

Then I had a wonderful postdoc who had a Ph.D. degree in computational numerics, but he also just did not want to do big computer codes. So I just evolved away from that style of analysis.

ZIERLER: How have you incorporated your interests in sustainability and ethics in your overall research agenda?

KIEFFER: The sustainability work hasn't been a research agenda as much as a—I don't know if you'd call it--a service. I got into it accidentally because a colleague of mine, Paul Reitan, who was very active in the geoethics community developed terminal cancer and died in 2011. The particular group I'm involved with is the Association for Promoting Geoethics and it is based in Rome. Paul asked if I would take his place in that group. Until recently, I was actually a Vice President of the IAPG. I've given a couple papers on sustainability issues, but mostly we just collaborate by email and support the people that are actively going out there and doing the work. It is a much more visible effort in Europe than in the U.S.

ZIERLER: I wonder if you might explain what geoethics means.

KIEFFER: Geoethics deals with the ethical, social and cultural implications of geoscience knowledge, education, research, practice and communication. It involves geosciences, sociology, philosophy and economics. But it's examining ethics both within research in the geosciences and in the broader application of that research in society. One side shoot is that ethical issues are being considered in the development of geoheritage areas.

ZIERLER: At a very broad level, as a theoretician, what are some of the most important advances in instrumentation or observation that have allowed the theory to develop over the course of your career?

KIEFFER: Although I am primarily a theoretician, I've had a few significant long-term projects where I've been in the lab building things (e.g., my work with Brad Sturtetvant and Joanna Austin at Caltech), and also some field work particularly at Mount St. Helens (after the 1980 eruption when I mapped the blowdown direction for the destroyed trees, and then later worked with Brad to develop lab analogs) and on the Colorado River after big flood of 1983. Theoreticians always need data against which they can test a theory. A theoretician in the geosciences faces a very different challenge than, say, many engineers, physicists or chemists. We're more like astronomers in that we generally can't control what data we have. We just have to take advantage of what's out there. Particularly in my case where I was looking at active processes like volcanic eruptions or floods on big rivers.

This is a little bit of a lateral leap, but as an example of this kind of accidental opportunity, in 1980 I developed my supersonic flow theory for the eruption of Mount St. Helens. Basically I proposed that the lateral blast of that eruption was like the discharge of a supersonic rocket nozzle through the north flank of the mountain. I had to teach myself rocket nozzle theory. In doing that, I discovered that in many textbooks, they use a semi-quantitative analogy between gas dynamics and shallow water flow in flumes. So I started studying that. Basically, with certain simplifying assumptions, the equations of conservation of mass and momentum are the same. I discovered that teaching geology students the shallow water flow theory first really helped then when I got to the compressible gas dynamics, because water flow is something they can go out and see. I can say, "Okay, when it rains in Pasadena, go out and look at the gutters in the street, and see what kind of waves you see."

I was developing that and thinking about this analogy when there was a big flood on the Colorado River through the Grand Canyon in 1983, only three years after the Mount St. Helens eruption. There had been a massive rapid snow melt in the Rocky Mountains, and the Bureau of Reclamation had to release more water through Glen Canyon Dam than they had released since it was built and closed in 1966. A huge wave—it was reported to be 15 feet tall—got set up at Crystal Rapids, about 9 miles downstream from Phantom Ranch. People were getting hurt. The Park Service eventually had to close the river to rafting. I just had this insight—I remember I was walking home through a meadow in Flagstaff when it hit me--that this wave was the river analogy to the shock waves I had studied in gas dynamics at Mount St. Helens.

What followed is actually kind of funny—I phoned the Park Service and said, "I think I know what's causing that wave. Can you get me in to see it?" Their reply was "Yes, if you'll tell us what to do about it." [laughs] So I had the rare privilege of being helicoptered down into the Grand Canyon. I sat at Crystal Rapids for a day just watching this wave. The ideas that I had sent me on a research program for about five years, documenting the hydraulics of the ten biggest rapids on the Colorado River in the Grand Canyon. Just another lucky convergence of my background with geologic events!

As another example of serendipity, I was studying the minerals that were formed at Meteor Crater by the impact of the Canyon Diablo meteorite. Quartz was transformed by the high pressures into polymorphs called coesite and stishovite and then melted glass. I needed to know the thermodynamic properties of these minerals in order to interpret some of my observations. The geophysicists were using theories for thermodynamics that Debye and Einstein had proposed. I tried applying these theories to quartz and they just didn't work, so I had to come up with my own theory. Eventually I brought in Raman and infrared spectra to look at the properties of how the atoms vibrated. That was just, again, an accidental outgrowth. I had the fortune that when I asked Gene Shoemaker, my thesis advisor, if he minded if I took some time away from studying the rocks to develop this theory, he just said, "Oh, you're a free person. Do whatever you want." That was a blessing! These thermodynamic papers were an accidental outgrowth of my Ph.D. thesis but are actually some of my most highly cited work. Again, it was one of these accidental things.

ZIERLER: Tell me about the origins of your blog Geology in Motion and specifically what does this medium, blogging, allow you to do that's not possible or better than the traditional ways that professors communicate, either in papers or conferences or in the classroom?

KIEFFER: The blog audience is entirely different from my normal "research" audience of peers. I haven't tried to find any statistics on its readership, and I really do it only for myself because it's a different style of writing and a way to communicate to a different audience. I can write more actively and informally on the blog. I use it mostly to look at current events and think about them a little bit. Blog posting also allows me to be a little weird, in terms of what I write about. I've been doing it for about ten years, and I have gotten a bit bored with it. When I started it, there were very few blogs. Now, there are blogs on almost every topic, geologically, that you want to investigate. I had a chance to take my blog over to the American Geophysical Union which has about a dozen blogs that they sponsor. My early "blogging colleague" when it was quite rare for geoscientists to do this, was a professor in England, and he did take his blog over to AGU. It's called The Landslide Blog. I decided not to take mine there because I wanted my blog to be fun for me to do, not a burden or commitment to anyone else. If I don't feel like writing on my blog for a while, nobody cares! [laughs]

ZIERLER: In thinking about your book The Dynamics of Disaster, and as a launch point for a more general question about your motivations, when is your motivation simply about the basic science, understanding geological and planetary processes, and when is it about specifically applying them to some benefit? Either preparation or sustainability or whatever can be the benefit of understanding these processes.

KIEFFER: I think the basic motivation for my research and publishing papers in the conventional media is curiosity. What has captured my curiosity? The motivation for the book and the blog is a desire to communicate and apply basic science. In my early career, communicating to the public was not as highly valued as it is now. If you look at the way people are, or were, evaluated for tenure, there's research, there's teaching, and then there is, often way down on the bottom, service. That has changed, I think, for the better. But there was always a part of me that wanted to do the outreach. Blogging is a blend of teaching and service.

Geoscience and Sustainable Infrastructure

ZIERLER: Two final questions before we go back and develop your personal narrative and family background. Two items really right hot off the press. In thinking about infrastructure, is the United States government listening to people with your area of expertise when they develop these enormous and enormously expensive infrastructure plans?

KIEFFER: One way that the federal government interacts with scientists is through the National Research Council, which is the operating arm of the National Academy of Sciences and Engineering (NASEM). That is a mechanism by which committees and panels bring in scientists to specific problems that the federal government has asked for help on. The committees formed are, most of the time, funded by an agency that has a need. But there is some money for the National Academy to initiate its own projects in areas they consider important.

ZIERLER: In the sense that so much of infrastructure needs to deal with resilience and preparedness against hurricanes and earthquakes and things like that, the question there is, is your sense is that the government is in contact with the kinds of scientists who know the most about how these things happen, where they occur, and how infrastructure might be conceived of to best mitigate those threats?

KIEFFER: I think there could always be more input by scientists, but I also see the government reaching out to scientists. Part of our job, as scientists, is to respond to requests, and many people do this without compensation by serving on NASEM committees. I know in my own case, that since I am primarily a theoretician, I have trouble getting far into the application side. How do I make my theory of supersonic flow from Mount St. Helens politically or operationally relevant? The question was, what difference does it make if the flow is supersonic versus not supersonic? You have to go through all of those questions in order to get into that operational stage. In the case of the supersonic flow at Mount St. Helens, the theory helps explain some of the unexpected damage in the devastated area. In the case of the Colorado River research, an analogy to supersonic flow helped in defining hazards on the River at different discharges from Glen Canyon Dam. Management insight and support for connecting the basic science to the infrastructure is critical.

ZIERLER: I'm not sure if you had the chance to read the recently published decadal report, Astro20202, and if more broadly conceived, if you have a sense of what's exciting, what the future might portend in planetary sciences?

KIEFFER: I think I'm going to bail on that. One of the collisions of professional and personal issues in my career was I was married to a planetary scientist in the days when nepotism was real. He went to UCLA into the planetary sciences department and I got a postdoc there in the Institute of Geophysics and Planetary Physics. However, because of the nepotism rules at the time, I couldn't be hired into Planetary Sciences, but I was fortunately hired into the Geology Department. Then we went to the U.S. Geological Survey in Flagstaff. He went into the Astrogeology Branch and, again because of nepotism, I couldn't be hired into Astrogeology. As a result of these circumstances, I've never been part of a spacecraft mission, or part of the support team, so I'm not really in a good position to make a prediction about the future of planetary sciences which is so dependent on NASA mission funding.

ZIERLER: Instead of making predictions in the future, let's go all the way back to Pennsylvania. Let's start first with your parents. Tell me about them.

KIEFFER: My father was a civil engineer who went to Penn State. He ended up working for a small company in Warren, Pa., called the Thomas Flexible Coupling Company. Flexible couplings are devices that are attached to rotating shafts. The shafts might have slight difference in their rotational speeds, and the couplings connect them and can absorb these little differences. He designed couplings and actually had a patent on one. My mom was a secretary. She was extraordinarily intelligent and capable, but she had six brothers, and they got the college educations. Both my mom and dad grew up within a 20- or 30-mile radius up in northwestern Pennsylvania in towns called Kane and Ridgway. They ended up in Warren which is 20 or 30 miles from Kane and Ridgway. I actually never got out of northwestern Pennsylvania until I headed west after my undergraduate years at Allegheny College, which was also in that tiny area of Pennsylvania. My mother pretty much stayed at home and raised three girls. I was the oldest. She was very demanding because she was determined that her girls would have the college education that she didn't get. Then after my dad died in 1973, she went back to work as a secretary, then eventually remarried and was able to pretty much stay at home at that point.

ZIERLER: Did your father involve you in his career at all? Did you have a sense of what an engineer did when you were a girl?

KIEFFER: No. My mother would not let me. I really, really wanted to go over to my dad's workplace where the flexible couplings were made, but I was absolutely not allowed. I was not supposed to go into science. Compounding that was that—and I'll probably never get over this—in junior high school, girls had to take home economics and boys got to take shop. I wasn't allowed to take shop.

ZIERLER: You wanted to?

KIEFFER: Well, yeah! I had to sew a pink linen dress! [laughs] It just—it was horrible. Then when I went to college, the girls were locked in the dorm at 10:00 at night whereas the boys could stay out all night. There were three physics majors in my class at Allegheny—myself and two boys. They could go to the lab and work all night, but I couldn't. That situation only got changed when a coed got killed in a car accident trying to get back to the dorm before they locked it in the curfew. After that they started letting the girls out of the dorms until midnight, but only on Saturday, something like that. I was pretty naïve about everything until I went west. I went to the University of Colorado for a year and then came out to Caltech.

ZIERLER: Was the program in physics strong at Allegheny?

KIEFFER: Well, it must have been, because I got accepted at Caltech right out of Allegheny! The University of Colorado offered me more money. Because I was on my own by then financially, I went to Colorado because it was more affordable. Also, a solar physicist named Walter Orr Roberts came to Allegheny as the Phi Beta Kappa speaker and persuaded me that Colorado would be a great place to go. Allegheny was a wonderful place for me, but I had never even read scientific journals while there so I was very naïve about research science. At the time, I wanted to be an astronaut and go to the Moon. I got to Colorado and discovered they didn't have any program that involved the Moon! It was all solar physics. The man I was working with at Colorado, Hal Zirin, got hired by Caltech to develop their solar research program in the astronomy department. He founded the Big Bear Solar Observatory. Hal asked if I would come out for the summer and do some site surveying to document atmospheric conditions for that potential observatory, so I spent a summer driving a pickup truck with a telescope around Southern California basically being at a site at dawn and then looking at sunspots as a measure of the visibility conditions.

Bob Sharp, who was the chairman of the geology department, then had graciously corresponded with me when I applied and even after I decided to go to Colorado instead of Caltech. So I decided to go up to his office in Mudd Hall and thank him for all the correspondence. He said, "Well, why don't you stay here?" I had broken up with my boyfriend in Colorado, so I stayed at Caltech! [laughs] That was a most unusual reason to decide to enter Caltech!

[Ed. Dr. Kieffer suggested including the following passage from Hal Zirin's oral history, interviewed by Shirley K. Cohen, Caltech Archives, February 1998.]

Zirin: And then Sue Kieffer (STET) —she was Sue Werner at that time—who had been a student of mine at Colorado, got a summer assistantship to come out here and work with me. I didn't have that much for her to do, so I suggested to Bob that Sue could work on the site survey. So Sue got a truck. They gave her a forty-five caliber revolver to stick in the glove compartment. She had a telescope. And she'd drive out every day to look at places. She'd set down the tower by jacking up the truck, actually, so it would be stiff, and make her observations and visually estimate the quality [of atmospheric stability]. At that time, Bob Sharp, the head of geology, was against women graduate students—he felt they couldn't do field work. But he saw Sue jacking up the truck every day, and he said, "Ah, this gal can do field work." I made the mistake of thinking that Sue probably was not good enough to come into astronomy as a graduate student, so she went into planetary sciences. Later on she married a guy named Kiefer, whom she eventually separated from. She's now a member of the National Academy of Sciences.
COHEN: [Laughter] You goofed.

ZIERLER: Wanting to be an astronaut as an undergraduate, were you taken by John Kennedy and the race to the Moon?

KIEFFER: Yep! I'm a child of the Sputnik era. When John Kennedy said he'd send a man to the Moon, I had no clue that he really meant a man. [laughs]

ZIERLER: [laughs]

KIEFFER: Basically, by the time I got out of grad school in 1971not only did I have a baby, but the manned space program had pretty much come and gone. That was just a dream that didn't get realized. But I have always told my son I just feel like I've been an astronaut here on Earth, because it's just such a wonderful place to explore.

ZIERLER: In making the leap from a small school as an undergraduate to being a graduate student at a large research university, first at Colorado and then at Caltech, did you see yourself at that point as pursuing an academic scientific career?

KIEFFER: I certainly saw myself as pursuing a scientific career. I had a resolution to try academia, government, and private sector. I did two of those three successfully—academia and government-- and discovered that I could not survive in the private sector. I have no skill at that! I have a lot of admiration for people who do. But I had a wonderful career in a couple of academic institutions and in the U.S. Geological Survey.

ZIERLER: Because you were a woman graduate student, in short order at Colorado and Caltech, being a woman in the mid 1960s at that point, did you find one institute more welcoming than the other?

KIEFFER: I have to say it's something I didn't think about. There certainly were instances that were uncomfortable or even nasty in growing into professional life, but generally I found people and the environment to be very supportive. When I had my baby at Caltech, Sam Epstein in Geology just turned into a pile of sugar whenever he saw that baby! [laughs] Fortunately, I had a really, really healthy child, so I basically went back to graduate school within a month after having my baby. Childcare was a real problem back then. We went through four different childcare situations in just a few months before we got one that lasted for four years. Then when we went to UCLA, it was the year they started their daycare center so that was a blessing.

ZIERLER: You mentioned Bob Sharp, of course. Were you no longer interested in solar physics? Was part of the move that you really wanted to get more into geology and planetary science at Caltech?

KIEFFER: Yes, I wanted to get into planetary science. My son is named Robert after Bob Sharp. When Bobby was born, Bob gave us a huge cast iron Dutch oven. He said, "Here, it's probably too big to cook in, but you can bathe the baby in it!" I think your question was about feeling welcome. The instances where I didn't feel welcome or there was some harassment just didn't weigh that heavily because there were so many other good things. I had a great, great experience with Gene Shoemaker. His wife Carolyn was so supportive of me and just welcomed me into their family.

ZIERLER: 1965, just to set the stage, are there any women professors in Planetary Science or Geology at Caltech at this point?

KIEFFER: There were no women professors at all in geology, or any other department, until 1969 when Jenijoy LaBelle was hired to each English literature. As far as female students, I think that the last year I was there the next woman entered into the geology program: Jo Laird came to work with Arden Albee in petrology. But then when I went to UCLA, there were two women professors—Helen Loeblich in paleontology and Margaret Kivelson in space sciences. So, being a woman professor was just a non-issue at UCLA. But it was nothing like the statistics now where a third to half the professors or more could be women in some of these institutions.

ZIERLER: In the mid 1960s in Geology, in Planetary Science at Caltech, what were some of the really exciting areas of research happening?

KIEFFER: Again, I ended up really not doing planetary science. I guess it was partly because I wanted to work with Gene Shoemaker, but my thesis was terrestrial—studying the rocks from the impact at Meteor Crater. Then when I got out of grad school, I was married and ran into this nepotism problem, so I never really evolved into planetary sciences. Even though my Ph.D. is in planetary sciences, I think of myself as a geologist. And, in the mid-1960's the exciting things were the products of unmanned space exploration, returned samples from the Moon, and plate tectonics, though Caltech didn't really get into plate tectonics until later.

From Caltech to UCLA

ZIERLER: What was Shoemaker working on when you connected with him?

KIEFFER: He was training astronauts. We had a great relation because Gene had basically very little time and gave me infinite freedom. I think out of that style of relationship, there were two consequences. I learned to work independently but I also developed a habit of working alone. That probably came back to bite me in that I've never been a member of a team, and I probably wouldn't be a very good team member because I just never had that experience.

ZIERLER: Was JPL relevant for your research at all at Caltech?

KIEFFER: No. I wasn't involved with JPL. As a grad student, I think unless you're studying with a professor who is involved with JPL, it's hard to get into a JPL project. In general, it used to be, and still is, somewhat difficult to even work across departments as a grad student. Ironically when I came back to Caltech as a professional in the 1980's, I worked with the aeronautical engineers and actually had an office in Aeronautics rather than in Geology. I came back and worked with Brad Sturtevant and we published two papers. Brad unfortunately died of pancreatic cancer. But his student, Joe Shepherd had a student named Joanna Austin who I now collaborate with. So the intellectual lineage from Brad is still there. Unfortunately, the pandemic really disrupted that collaboration because I haven't been able to go to Caltech for a couple years.

ZIERLER: On the social side, in the late 1960s and early 1970s, Caltech was certainly not as political a place as, say, a Berkeley or a Harvard. Were you politically active at all during those years?

KIEFFER: [laughs] I was too busy being a mother and a student! [laughs] I have always voted and had opinions, but no, I was not a Berkeley-style activist, except that I marched in the Martin Luther King "I have a dream" march in 1963 while I was still an undergraduate. I don't think there was much political activism at Caltech in general back in the 1960s, but I was so busy that maybe I just didn't see it. I don't know how much there is today.

ZIERLER: What was the process for you developing what would become your thesis research?

KIEFFER: [laughs] It's a classic Gene Shoemaker story. I basically said that I wanted to work with him. Gene had so many ideas that he could just pull them out of his pockets for others to work on. Gene had done his Ph.D. work on the geology and formation of Meteor Crater. Gene hated looking through microscopes, as far as I could tell, and he said "Oh, you can look at the shocked rocks from Meteor Crater." I had never had optical microscopy! Actually, I hadn't even had Geology 101 when I went to Caltech. So, I ended up working on the microscopy. Then I told Gene I wanted some field experience. He said, "Oh! I have a project you can work on." This is number two out of his pocket! "Let's leave tomorrow to go to Canyonlands, Utah." So, off we went to Canyonlands, which he thought was an analog to the Basin and Range geology structure. We drove up there in two cars, me and Gene with Carolyn and their son, Patrick, and some USGS supplies. Canyonlands is 4-wheel drive country. We drove in four-wheel drive Jeeps for four hours. I had never driven four-wheel drive! We got to the site where we wanted to set up a camp and unrolled the tent that I would be living in alone for 4-6 weeks. It was like a six-man tent that had no tent stakes! I said "Gene, I think you forgot something!" After one day there, Gene and family left to go back to Flagstaff, and I had to drive back out to Moab for those darn tent stakes! Those were two projects I worked on with Gene and I enjoyed them both. Bob Sharp never forgave Gene for sticking me out in Canyonlands for the summer. He just thought that was no place for a woman! [laughs]

ZIERLER: Besides Gene, who else was on your committee?

KIEFFER: I don't remember. I know Barclay Kamb was, because I did a lot of my thermodynamics work with Barclay. Bob Sharp was on it and probably someone from outside the department. I don't know how many there would have been.

ZIERLER: After you defended, what opportunities were available to you? What did you want to do next?

KIEFFER: I was offered a postdoc by a professor named George Kennedy at UCLA who ran a high-pressure lab. Bob Sharp told me, "It's going to be a wild ride if you go work with Kennedy." I kind of thought, "What could be wilder than five years at Caltech?" [laughs] Kennedy had a high-pressure lab with an apparatus called a piston-cylinder. We could compress minerals up to about 30 kilobars pressure. That was a high enough pressure that I could have synthesized the minerals I was working with from Meteor Crater. But when I showed up for work with Kennedy, he said, "Oh, I don't want to do that project. How would you like to measure thermal conductivity of minerals?" My reaction was "What?" But I had no recourse, so I spent two years measuring thermal conductivity of minerals at high pressure. In order to calibrate the technique I was using, I used Teflon for my standard. I'm very proud of the fact that the non-geologic material "Teflon" appears in my CV! Then I got lucky again. Kennedy and I got into a huge fight in the hallway because he took the money from an NSF grant that I had written to support my postdoc work there, and used it for another postdoc. I called him on it. He said, "You're fired" and I said, "I quit." I'm not sure who said what first. But that caught the attention of the Geology Department and actually resulted in me getting noticed, and then hired, by the Geology Department.

ZIERLER: In a tenure-track line?

KIEFFER: Yep. It was an affirmative action position, which kind of got my nose out of joint, but the chairman said, "Look, I can't politically hire you into the regular position when I can get you on affirmative action and another person in the regular position, so I can get two instead of one." So I accepted that and was grateful. As I've matured, I've realized that was certainly the right decision, but my ego just didn't like the idea that I had an affirmative action position at that time.

ZIERLER: What was your research at UCLA? What did you focus on in the 1970s?

KIEFFER: I went back to the Meteor Crater rocks and shock processes in general. The transmission electron microscope had just been developed, and so John Christie, Prem Phakey and I looked at the whole suite of shocked Coconino Sandstone from Meteor Crater and published what may have been the first paper using the transmission electron microscope to tell the story of a suite of rocks. The other project that I worked on was fleshing out the thermodynamic ideas that that I had started on in my thesis, resulting in five long papers on mineral thermodynamics.

ZIERLER: Why did this resonate? As you mentioned earlier, this was some of your most highly cited work. What was it about it that resonated beyond your immediate field of interest, to the field?

KIEFFER: At the time, there were no really good models for the thermodynamic properties—say heat capacity, entropy—for complex minerals. Geophysicists were using models that Debye and Einstein had proposed but those models were only for materials that had very simple structures—substances like sodium chloride. I was looking at minerals that had really complex formulas and structures: the polymorphs of quartz, feldspars, garnets, and micas. There just weren't models for any materials so complicated. It was just the right time for that piece of work to evolve. Again, I was just really lucky.

ZIERLER: When you were promoted to associate professor, to what extent did that serve as a corrective to your feelings about being hired from a diversity point of view?

KIEFFER: Those feelings went away the minute I got hired into the geology faculty, because I was embedded in a group of wonderful people. My office on the fourth floor of the Geology Building at UCLA was adjacent to the structural geologists and petrologists. These were wonderful faculty colleagues—John Christie, John Rosenfeld, Gerhard Oertel and Ron Shreve. I was treated completely as an equal professional from day 1. It was really, really supportive environment. I'll tell you how supportive: The year that I came up for tenure, my postdoc advisor, Kennedy who I'd had the hallway fight with, inserted a letter into my tenure file that said I hadn't shown up for work for six months. Letters can't be removed from a tenure file. One day another professor came into my office and said, "Sue, do you have any lab notes for January to June of ?" I think it was 1973. He said, "I need them." I said, "My lab notes are a mess." He said, "I don't care." They Xeroxed all of my lab notes for six months and inserted them in the tenure file. Eventually they told me all about this. So, UCLA was just a wonderful, wonderful place for me. Then I went from there into a very supportive environment in the USGS.

ZIERLER: How did you get involved with the Geological Survey?

KIEFFER: Two things. We wanted to get out of Los Angeles to raise our kid, who was six or seven at the time. The USGS leaped at the chance to get my husband to become branch chief eventually of the Astrogeology Branch. I went to Flagstaff with no job and had been rejected by three Branches of the USGS basically because if any positions became available in a Branch, they already had people in mind for them. A man in the Reston office of the USGS, Dave Stewart, knew of my thermodynamics work and hired me to be in the Experimental Geochemistry and Minerology (G&M) Branch, headquartered in Reston. I became what was called a "branch orphan," working by myself in Flagstaff. But the funny thing was what Dave said to me in the process of hiring me—both my husband and I should have gone, probably, into a GS-14 position because we graduated only a year or two apart at Caltech. That's on a GS-scale of 13, 14, 15, and then supergrade. My husband went in as a 15. Dave said, "I'm going to hire you as a 13 because you'll probably only have one promotion and I want to control it." I just said to myself, "Watch my dust" and I went 13, 14, 15, supergrade, in about ten years. After that initial hiring glitch, the EG&M Branch was just a totally supportive environment.

ZIERLER: To leave an associate professorship for no job in Flagstaff, as a woman, is that something that really is a sign of the times? Was that something that if it was today would you have ever done that?

KIEFFER: It was not quite as cut and dry as that, because I think we took a leave of absence from UCLA rather than just resigning. But yes, it was a leap of faith. Plus, Dave Stewart came in to try to hire me fairly quickly after we made that decision to move, so I wasn't in limbo very long. I liked the freedom of being a Branch orphan, having no bosses around to look at what I did. Although it was quite a lonely existence, it was also very academically free.

ZIERLER: Which is interesting, because often times in government positions, there's a mission and you need to be responsive to that mission.

KIEFFER: Yes. And I would have had to be responsive to missions if I was in the planetary sciences field, because the whole Astrobiology branch of the USGS was funded by grant and contract money from NASA. But I'm a cheap scientist. I'm a theoretician so I don't need a lot of money.

ZIERLER: By the early 1980s, with that academic freedom, what did you want to focus on, and in what ways was being at the Geological Survey an opportunity for you to work on those areas?

KIEFFER: I was trying to focus on the idea that I had that Old Faithful geyser could be a volcanic analog. Basically, almost all of the planetary problems that I did eventually work on were in that window of the 1980s, early 1990s. My Old Faithful work kept getting interrupted by geysers and volcanoes erupting all over the solar system: Io in 1979, Mount St. Helens in 1980, Triton in 1990, and then later Enceladus in 2006. Then, in 1983 I started some major work on river hydraulics. I would bounce back and forth between a couple different projects.

ZIERLER: I'm curious when you were a visiting professor back at Caltech in the Winter of 1982, what that felt like to be back at Caltech at a different stage in your career?

KIEFFER: There's a big difference between being a grad student and a recognized professional. I was pretty well-established by 1982. And, I was back there with strong connections in the Aeronautics Department where I had basically no grad student history. I didn't have to overcome anything because I was a brand new person there. It was interesting how that aeronautics connection came about. I went back to visit Caltech in 1980 or 1981, to give a talk, maybe in Beckman, about my supersonic flow theory for the lateral blast at Mount St. Helens. Brad Sturtevant came up to me afterwards—and I quote him exactly—said, "That is pure bullshit." Fortunately, I pulled myself together and said, "Prove it." Then we started a lab program to simulate volcanic jets and Brad became a real supporter of the supersonic flow ideas. Brad also had a hidden desire to be a geologist, and he loved the outdoors. We went to Mount St. Helens after the 1980 eruption to look at some features and he would just grab a shovel and start digging into the sediments. He was just very talented and bridged between the theory and the lab and the real world in a fairly unique way.

ZIERLER: When did you start to get involved in researching geomorphic evolution in Grand Canyon?

KIEFFER: 1983 when there was a big flood along the Colorado River. I had been studying the supersonic nozzle theory for the lateral blast at Mount St. Helens in 1980. Supersonic flow is quite different from subsonic flow, especially in the existence of shock waves. There is a hydraulic analog of shock waves in gas to big standing waves in rivers so I had been teaching myself hydraulics. In 1983, I heard about this big wave in Crystal Rapid, went down there, did the analysis, and then realized that not only was the river flow of interest but how the river was eroding its banks. That gave me the idea that I could use the properties of the river as it went around these piles of debris in the rapids as a measure of the size of the floods that had carved the river channel.

The rapids in the Grand Canyon all occur at a place where a tributary has had a flash flood that dumped a lot of rocky deposits into the main channel of the Colorado River forming a constriction. For the big side canyon floods, those deposits actually temporarily dam the main channel of the river. Then successive floods on the Colorado River eat away at those damming deposits. A little flood takes away a little bit of debris and widens the channel a little bit, and a big flood takes away a lot of debris and widens the channel a lot. I got the idea that I could measure the constriction in the channel as a measure of how big a flood the channel had seen. I came up with a number of 400,000 cubic feet per second as the largest discharge that had occurred since the debris deposits were emplaced. Later some independent studies came up with the same number or a similar number. That project morphed into a study of the ten largest rapids on the Colorado and it certainly was a lot of fun. Again, it was one of these accidental things that just kept falling into my lap.

ZIERLER: What did it feel like when you were elected to the National Academy in 1986?

KIEFFER: Oh! [laughs] It was funny. Gene Shoemaker came into my office with an armful of red roses [laughs] to tell me. It was interesting because I had not heard much about the National Academy at the time, except that while I was a postdoc at UCLA one professor at had gotten inducted into it and I knew there was a lot of celebration. But I hadn't been involved with the Academy and hadn't thought about it, so it was a complete surprise.

ZIERLER: Did you appreciate at the time how special it was given how relatively young you were to be elected?

KIEFFER: I guess I didn't think about it much. I think that's the only answer I can give you. It was more a feeling of "What have I done to merit this?"

ZIERLER: What impacts did you see or did the National Academy see your shock wave work as having?

KIEFFER: I don't think I can really address that because I don't know any details of the nomination.

ZIERLER: In the late 1980s, you are heavily involved in hydraulic maps of rapids. I wonder if you can explain technically the process of constructing these hydraulic maps.

KIEFFER: Again, it was an accident of the environment in Flagstaff. The planetary maps that Astrogeology was producing were created by a very talented group of airbrush illustrators who could interpret images taken from a moving spacecraft. These people were experts in taking spacecraft images and reconstructing them into a geologic map. The discharges into the Colorado River are controlled by Glen Canyon Dam. They vary from about 3,000 cubic feet per second (cfs) to about 30,000 cfs, and then during the 1983 flood, they went up to 90,000 cfs. My idea was to make maps that showed the rapids at these three different discharges—3,000, 30,000, and 90,000 cfs. We had air photos of the rapids at one of these discharges, or maybe two of them, but we didn't have them for the 1983 flood. So, I walked over to the air brush folks and said, "Could you use your techniques to take observations from the helicopter flights over the river rapids and help me with mapping the features of the discharge at 90,000 cfs?" It was really that good fortune of being near that talented group of planetary airbrush folks that I was able to plug into. They really enjoyed the project too, so it worked out really well.

ZIERLER: One paper you gave which is intriguing—when you were talking about studying geologically rare events, the difficulty in understanding them, I'm particularly interested in your focus on the importance of what you called establishing institutional memories of these hazards. What does that mean in this context—institutional memories?

KIEFFER: The funny thing is I can't remember what paper you're talking about!

ZIERLER: This was in a workshop on telluric disasters in Paris in 1989.

KIEFFER: Oh my gosh, well, that was a long time ago and that's why I can't remember it! That was a conference in the Versailles Palace that Al Gore came to for one day! The problem is that the attention span of humans as individuals is a year or two. If you have a disaster, you basically have a year or two to try to change human behavior, and then interest fades. Institutional memories can be longer, but they're not very long compared to the relatively long time span between rare events. The question I was pondering then was: if you have a Meteor Crater event every 50,000 years, or you have a Mount St. Helens-scale event—globally, they are roughly every decade, but in the U.S., they are not that common. The question was: how can we get institutions to be ready for the next rare event? I think in the hindsight of 30, 40 years since Mount St. Helens and the Colorado River events, we're still not all that good at it. I think that the way we deal with rare events is to just hope that we can extrapolate the experience we have for the more common events and make a leap of faith into the next one, the bigger one. So, I wouldn't say we've made very much progress on that.

ZIERLER: What was some of the work in the early 1990s on lattice dynamics in minerals?

KIEFFER: My thermodynamics papers were 1979-1982. Those were the early days of supercomputers being brought into earth sciences. My theory involved small models on a desktop, but I could see that the future of lattice dynamics was going to be heavily into computational techniques that were beyond my capabilities and my understanding. I didn't have a background in either minerology and lattice dynamics, I felt that the field was going to move pretty quickly and there wasn't going to be a place for me in it. I've been surprised how durable those papers have been. I Googled the other day, because I was thinking about this conversation. In some of the Asian countries—China and Japan—those papers are still frequently cited. I keep thinking maybe they're perhaps being used as a teaching tool. The papers start with a review of the lattice dynamics theory, progress into a review of the lattice vibrational properties and spectroscopy, and then finally the last three papers actually move into applications. I'm pleasantly surprised they are still being used.

ZIERLER: In 1993, you wrote in Geotimes about exploring Earth with new data and new tools. What was new at that point? What were some of the new tools, and what kind of new data were you working with?

KIEFFER: [laughs] You should have told me which papers you were going to quote. 1993?

ZIERLER: This is with Morrissey.

KIEFFER: I can't remember where that was even published. You said it was 1993?

ZIERLER: In Geotimes.

KIEFFER: I think that paper was a communication effort. I can't remember if it was invited or how we did that. Megan Morrisey was a grad student at that time. We were trying to introduce what we felt we could do with computational techniques to a broader geoscience community.

ZIERLER: In 1995, in what I assume was a tongue-in-cheek title, Journey Toward the Center of the Earth—what was happening in the mid 1990s with regard to Earth's inner core and research in it?

KIEFFER: I don't know regarding the inner core. That was indeed a tongue-in-cheek title! We were reporting on the results of a probe that we lowered into the conduit of Old Faithful geyser and used that title just as a takeoff of Journey to the Center of the Earth. We were going down all of 60 feet. [laughs] I never got into geophysics research on the Earth's interior.

ZIERLER: Do you have a specific memory of when your research, either by your own realization or by some of your colleagues, was relevant for other planets in our solar system? Roughly when that started to happen?

KIEFFER: No, because I haven't followed the planetary research that well, with one exception. My thesis meteorite impact work has been used, criticized, and expanded upon by a Canadian group led by Gordon Osinski. The Canadians have always been very active in meteorite research because they have a lot of impact craters on the Canadian Shield. Because of glacial erosion they can go and look at these craters. Osinski has probably been the planetary scientist who has looked at my work the most carefully. He evolved the ideas that we had put forth on two big impact craters, at Sudbury in Canada and Chicxulub at the Yucatán. He really dug into the things we had proposed and I think made some legitimate criticisms and adopted some good ideas, too. That's the way science should evolve.

ZIERLER: What was your decision to join the faculty at Arizona State in 1990? Were you looking to get back into an academic environment?

KIEFFER: I had been interacting with people at ASU so it was a logical place to look at. My son was out of the nest at that time and so for the first time since I was a grad student, I had the freedom to go without constraints.

ZIERLER: Did your research change, or were you able to take the same research with you to Arizona State?

KIEFFER: I didn't stay at Arizona State very long. I got recruited to become department head at University of British Columbia. That was fine. I decided that was an adventure. At the time, women were just starting to move up into the higher administrative ranks in academia. A number of my female peers were looking at that same kind of move upward, for example becoming a department head. I discovered very quickly that academic administration was not my forte.

ZIERLER: How long did you stay in that role?

KIEFFER: I think the answer is one year, six months, and one week!

Putting the MacArthur Fellowship to Good Use

ZIERLER: Right at this time, you are named a MacArthur Fellow. What was that like and what did that honor allow you to do?

KIEFFER: Well, what it allowed me to do was get refocused and relocate. I used my MacArthur money to fund a project teaching science to homeless and at-risk kids with a teacher friend of mine in the Phoenix area. I spent a year commuting and doing the equivalent of Zooming, except you couldn't Zoom back in those days. We set up a weekly email with me and the class. I became "Scientist Sue" to these kids. The teacher would guide them to ask me questions about science. The kids basically had no math skills, very limited reading skills. They were typically eighth graders with fourth grade reading and almost no math skills. This was the challenge.

And maybe this comes back to your question a long time ago about my communication, my blog, trying to convey science. One of the things we discovered was these kids absolutely loved stories about my dog. So there were all these creative ways we tried to teach science using the antics of the dog, or whatever was going on. In one instance—this is not a dog story, but a fire extinguisher story—I was driving down a highway at 50 miles an hour, and the person in the passenger seat set their briefcase down on the fire extinguisher that I kept in the car. It detonated inside my car! We told this to the kids. Well, it turned out I didn't have a clue as about the mischief that they knew how to do with fire extinguishers! So that episode, which had captured their interest, got turned into a lesson about the chemistry of fire extinguishers.

ZIERLER: At what point did you realize that this project would become a private-sector endeavor? What the MacArthur Fellowship allowed you to do?

KIEFFER: Well, it wasn't really a private sector. I was using the Fellowship money for travel. I can't remember even what I used it for other than that, but it went basically toward that project. I didn't use it for my own salary.

ZIERLER: Did you stay active in the research during this period, or you really took a hiatus?

KIEFFER: Oh, no, the homeless and at-risk kids project didn't take that much time so I could stay active in my research. I remember one thing we did—again, remember the old technical challenges of the time, but we printed out all of the email correspondence and made a little book out of it. But then nothing ever happened with the book and we just kind of dropped it.

ZIERLER: Then in 2002, what were the circumstances of you moving again to the University of Illinois?

KIEFFER: I had relocated from Vancouver, British Columbia, to a very small-town northwest of Toronto and was trying to work alone. As I mentioned, Canada didn't have the kind of planetary program that I was hoping to work in. I was feeling increasingly isolated and realized that as one gets older, it's harder and harder to self-correct. If you're working by yourself, it's easier to make mistakes and not be able to catch them. I was feeling and thinking about that sense of isolation and communicating with my friend, Chuck Simonds, in Houston that I was thinking of coming back to the U.S. Chuck has been a friend and colleague since the 1970s, and he got his Ph.D. at Illinois. By coincidence, he was communicating with his best friend from grad school days, Jim Kirkpatrick, the science dean at Illinois. It was coincidentally the time the Walgreen funds had just been given to Illinois to recruit senior people, and so I was offered an endowed chair. Again, it was just one of those fortuitous happenings.

This conversation is making me realize over and over how many really good things have dropped into my lap. It has been an amazing 50 years of professional research.

ZIERLER: When you got to a point of reflecting on, for example, volcanism—volcanoes both on planet Earth and elsewhere in the solar system—what were some of the obvious commonalities, and what made Earth volcanoes unique?

KIEFFER: That's a little different than you asked a while ago, when I commented that the Earth is unique because of all of the biology. Earth's volcanoes are very similar to some extraterrestrial volcanoes, like the volcanoes on Mars, except for the gravity field and atmospheric conditions. But they are very different from others like the volcanoes on Io that are the sulfur and sulfur dioxide-driven ones. I should say that there's now evidence that there is also magma--melted rock--on Io, but it has got sulfur in it instead of water and carbon dioxide like we have in volcanoes on Earth. Thinking about the volcanoes on different planets has been very helpful to volcanologists and planetary scientists. It's a complementary exercise. A lot of the planetary scientists I know who study volcanoes, for example, like Ron Greeley at ASU, were very firmly rooted in terrestrial analogs. If you're a theoretician or extrapolating to other planets, it's really easy to get carried away and not be able to test your theories and let your imagination run a little too far if you can't test them against terrestrial analogs.

ZIERLER: As you emphasized, one of the distinguishing factors of course on Earth volcanoes is the existence of life here. To what extent does your research get us closer in understanding questions about astrobiology with regard to volcanoes or ice or any other features in other planets that might give us signs of life?

KIEFFER: I think the most relevant is my geyser work, not my volcano work. The new work going on with extremophiles that live in these very hot, very acidic environments is a really exciting field of research. To some extent, my work on geysers constrains that. One of the projects that never worked out was that I had successfully put the probes into the conduit of Old Faithful geyser. That took a lot of approval by the National Park Service. You don't just stroll up on Old Faithful. I worked very closely with the Yellowstone administration and with the park geologist, Rick Hutchinson, to get both the pressure-temperature probes and the camera permitted to go into Old Faithful. We never had a problem. We never lost anything, except a sock that we quickly recovered, which is another story. We produced results.

I came back to the Park Service years late when the administration had changed, and said, "I think there could be life in the conduit of Old Faithful. Could I have your permission to go down just with basically a swab and touch the side of the conduit? I wouldn't go as far as we have been before." It was a simple, trivial experiment. The administration just said, "No, we're not allowing any more work in the conduit." And that was it. I couldn't budge them. I tried to say, "I think it would be extremely interesting to the public if you had an answer to the question "Is there life in Old Faithful.?" "There's no answer at the moment. From the video camera observations, I saw suggestions that there were textures that looked like they could be these biofilms that they see in other thermal features. But that just came to a dead end.

ZIERLER: By 2014, when you were writing about the deadly dynamics of landslides, what aspects of your previous research were most relevant to studying the dynamics of landslides?

KIEFFER: One of the things I discovered in writing my book, The Dynamics of Disaster, was the thrill of learning about completely new things that my research would never ever have taken me into. I came across this phenomenon called "quick clay" that is quite common around the Arctic Circle but I had never heard of it. I got totally intrigued by quick clay—there's a fantastic video on-line of a farmhouse sitting on the ground, and all of the sudden the substrate liquified and the farmhouse just floated away. It's a particular type of clay that is formed when seawater is involved. When rain dilutes the seawater in the clay, it changes the properties of the clay and you get these catastrophic landslides. I got totally intrigued by that. So, it was an outgrowth of writing my book that led to this article; it wasn't any research of mine. But the funny thing was I then discovered that here on Whidbey Island, where I live, there's actually a very small outcrop of quick clay down on one of the beaches. I went down to look at it and discovered that the easy way to ruin a pair of boots is to walk in quick clay, because when it dries out, you cannot get it off your boots. It's just the most amazing stuff! So yeah, that particular article was an outgrowth of my book and the delight of just learning about this weird thing.

ZIERLER: That same year, you were awarded the Penrose Medal. Part of the citation is, "For eminent research in pure geology." I wonder if you can define what "pure geology" means and how your research fit in with this citation.

KIEFFER: The Penrose Medal was really meaningful to me in two ways. One was I was the first woman since its inception in 1927—almost 100 years before. Now there has been a second woman, Tanya Atwater. But the second way was that I had previously been recognized for my work in applying physics and chemistry to geological problems with the Day Medal, but I always wanted to be a geologist, and it was like the Penrose Medal said, "Ah, you made it! You finally can call yourself a geologist." So yeah, that was really nice.

ZIERLER: To return to your work in geoethics, was there a particular controversy in the field, falsification of data, some specific origin event, that created this need for a sub-discipline or a particular focus in what is now called geoethics?

KIEFFER: There was, and I can't take any credit for it, but there was the earthquake in L'Aquila, Italy, that resulted in scientists being put on trial for manslaughter. There was a huge kerfuffle in Italy about the responsibility for what had gone on. One of my colleagues, Paul Reitan at SUNY, Buffalo, had been involved with the Italians as they tried to figure out what the ethical responsibilities of geoscientists were in these catastrophes. Basically geologists do geology. They're not the people who should be calling for emergency response such as evacuations. There was a need for all of these lines of responsibility to get defined and sorted out. The origin of geoethics was that very specific event in Italy. That's why the center for the International Association for Promoting Geoethics (IAPG) is in Rome.

ZIERLER: Just to bring our conversation right up to the present, I know you've been working on volcanology most recently. Can you talk a little bit about that?

KIEFFER: If you look at volcanoes that are young enough that they don't have vegetation, and if there is any rainfall around, the rainfall will erode gullies into the flanks of the volcanoes. Rainfall gullies have a very characteristic appearance—they have a dendritic structure, for example, little tributaries coming into a main gully. There is a volcano called Volcán Bárcena off the coast of Mexico that erupted in 1952 and the "tephra avalanches" that flowed down its flanks created very linear channels with no significant tributaries. The gullies just did not look like they were produced by rainfall, and they appeared very quickly after the eruption rather than after a prolonged rainy season. Again, this was an eruption in 1952, so there weren't a lot of observations. A geologist, Adrian Richards, got taken there by the Navy. He published a volume on the geology of the whole island on which Bárcena exists, and it included some pictures of these channels on Bárcena. He listed why he didn't think they were caused by rain. We picked up on that. I was working with a colleague at UC Santa Barbara, a fluid-dynamicist, who had been working on turbidity currents, which are basically debris flows that go underwater. He was thinking about erosion at the bottom of a turbidity current, the boundary layer of the turbidity current with the ground. We had never met but we got corresponding and eventually met and became such good friend that he and his wife have come up to my home on Whidbey Island for a visit. We came up with this idea that we could apply the turbidity current ideas that he had already published to these linear channels on Volcán Bárcena. That was the paper that just came out earlier this year. But it took us two years to do it. It was a labor of love.

ZIERLER: Now that we've worked right 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 then we'll end looking to the future. As you noted before, luck has played such an important role in the many twists and turns of a research career that has been quite eclectic, all the things that you've worked on and when you've worked on them. In looking back at all of them at a very broad level, what are some of the connecting threads, either scientific discipline or your style or intuition, that might serve to connect all of this research?

KIEFFER: Except for the thermodynamics research, I mentally have said, "I like processes that involve things that move very fast." So, it's a volcanic eruption, it's a big river flood, it's a meteorite impact. Then under that sort of casual description, it's basically fluid dynamics. These are processes in which things move and they have to obey certain laws of motion. I like the challenge of trying to figure that out. It has been a fun career. Because other people, and other scientists, really like things that move, too. The underlying commonality is the fluid dynamics.

ZIERLER: If you could go back all the way to your graduate school days at Caltech to the present, what were some things in the field—geology, planetary science, volcanism, take your pick—which were really poorly understood or even mysterious 50 years ago—when you look back at them, what is truly understood now that wasn't then, and what remains mysterious or poorly understood?

KIEFFER: I think that 50 years ago, very broadly, the equations of motion to govern anything moving had solutions for two extremes. One extreme is that gravity drives things downhill. The other extreme is that gas in a system can expand and drives things by expanding. These are basically referred to as the end members of gravity and gas-driven flows. I would say that 50 years ago, most of the geoscience community did not study or invoke compressible fluid dynamics, that everything tended to be interpreted by reference to gravity. All of geophysics of the earth's interior was gravity-driven or was dealing with gravity-driven processes. The mantle has parts that go up and down. Most students were not taught about the science where compressibility plays as much or more role than gravity. What I've seen now is that there's much more exposure of geologists and geology students to some of these ideas that there may be a complementary process to gravity that involves gas expansion, that is, compressibility.

ZIERLER: The Penrose Medal cited your contributions in very poetic terms, talking about your work both at the microscopic scale and the megascopic scale. I wonder if you could reflect on how you've chosen projects at both scales. What are the connecting points and where are the real differences in these scales?

KIEFFER: A long time ago, I co-edited a book called From Microscopic to Macroscopic. That was in the thermodynamics area where we were looking at properties from the atomic scale to material sciences scale. How do I choose my projects? I don't really choose my projects; they just sort of land on me. If I could choose my projects, I would have finished this Old Faithful work decades ago. So I'm not sure I can actually answer that question without thinking about it more.

ZIERLER: Do you see the fields differently, the microscopic and the megascopic or macroscopic? Or is it all geology?

KIEFFER: I'd put it the other way. I think the only thing that has a broader range of scales than geology is astronomy. Geologists really look at things from the atomic scale to the solar system scale, and we potentially think about planets beyond the solar system. There's a pretty clear boundary between geology and planetary science, on the one hand, and astrophysics on the other hand. I don't know many geologists who do astrophysics. It kind of stops at the planetary science scale.

ZIERLER: In your message upon receiving the Penrose Medal, you write that "our collective work in the geosciences has made and must continue to make a difference in how humans interact with our planet." What were you thinking of? What is that difference that geoscience has made, and what should it make in the future? That's your final comment. That's what you left us with. "Our work in the geosciences has made and must continue to make a difference in how humans interact with our planet." I wonder if you meant more philosophically, like an appreciation, or there was something actionable you saw in terms of our relationship, how we live on the planet, how we use the planet's resources?

KIEFFER: I think it was more operational, that as our understanding of the Earth has increased, so has our understanding of the impact that the Earth has on humans and humans have on the Earth. I think we need to continue to push that. It breaks my heart when I see stupid regulations, like allowing and rebuilding in places that are in great danger from geologic hazards. When New Orleans was hit by Hurricane Katrina, the intellectual part of me says, "No, you shouldn't rebuild in New Orleans, because it's going to have another Katrina." The operational part of me says, "You can't replace the culture and civilization of New Orleans. You just can't move that somewhere else." So there's this conflict between what appears to be clear-cut and what actually has to be made to work as best we can operationally.

ZIERLER: Last question, looking to the future—as you said before, projects land in your lap, so there's a certain lack of agency, if you will, for determining what you work on next. To the extent that you do have that agency, that you do have a good sense, for however long you want to remain active in the field, what do you want to accomplish?

KIEFFER: Besides getting my Old Faithful work done? [laughs]

ZIERLER: Maybe that's it!

KIEFFER: I am very focused on it. I have a good friend here who I have interacted with on sustainability issues. He and I actually Zoom weekly. We were talking about bubbles. I said, "There's this crazy hypothesis that's out there that has been discounted, but people were worried that in the Bermuda Triangle, a ship would go in, a bunch of bubbles would come up, and the ship would sink." He got carried away with that. He says, "Oh, I have a friend in Korea who's working on using bubbles to break up mats of algae." The next thing I know, he invites me to become a collaborator on a project that involves using bubbles to break up mats of algae. I said, "No!" I mean, it's an answer to your question. I'm not doing anything new until I get the Old Faithful work out.

ZIERLER: What will that look like, the final product, as you envision it, for Old Faithful?

KIEFFER: I think there's probably several publishable papers. The one I'm working on right now is that we have enough observations to construct a schematic diagram of how the conduit fills up as the geyser recharges toward the next eruption. This model is very different than a model that was published within the last few years. That's going to be the first paper. Then the data I have are pressure and temperature at eight stations going down the conduit, so we have information about the recharge process in detail. I think that will be the second paper—how this recharge actually works.

Then the third paper which I'm not sure I can pull off—our probe actually got stuck briefly during an eruption and we got some really interesting-looking data, but the probe also got thrown out, so I'm not sure what was going on in the conduit or exactly where the probe was, and I'm not sure if I can reconstruct that. Unfortunately, both colleagues in this project have died and a lot of the data got lost. I'm working it out on just random pieces of hard-copy paper that I have. I'm just not sure how much I can do with that or how anything I come up with could actually be tested. But I figure by the time I get to the third paper, I'll be lucky if I can still think! [laughs]

ZIERLER: Just to broaden that out, best case scenario, with the publication of these papers, what will we understand about Old Faithful that we don't currently understand?

KIEFFER: I tried to convince the Park Service—when I told you about this failed project to look at the biofilms, I said, "Individual geysers have a finite lifetime, a few hundred years if you're lucky." If you look down on the mound of Old Faithful, there are indications that there have been other eruption vents there that had died, and the activity moved sideways. I think my work will contribute—I hope it will contribute—to understanding what the conditions in the conduit are and could possibly become. The reason the geysers die is that they get filled with mineral deposits of silica and they seal themselves shut. I'm hoping my work will shed light on conduit conditions and what to look for if the geyser is starting to seal itself shut, and I try to make that as relevant as I can to the goals of the Park Service. Unfortunately, I've lost all my contacts up in the Park now because it has been decades since we did this work. I'll try to get it published and then see where we can go with it. Hopefully it could influence Park Service decisions in the future.

ZIERLER: On that note, it has been a great pleasure spending this time with you. I'm so glad we were able to connect and you were able to share all of your perspective over the course of your career. Thank you so much.

KIEFFER: Thank you, too, for the interest, David.

[END]