Grand Canyon Caving and Other Adventures: An Interview with Carol Hill


Kathryn: As a cave expert, you’ve spent a lot of your career underground. How did you get interested in caves? Did you know you wanted to become a geologist from a young age?

Carol: No! I thought I wanted to be a nurse. In the 1950s women could realistically only be teachers, nurses, stewardess, and housewives. I found out I hated nursing, and “just by chance” we went to Mammoth Cave for Alan’s graduation, met some cavers, and became active in spelunking. That sparked my interest in geology, and I started taking geology courses at the University of Michigan.

When we moved to Albuquerque in 1967, we already knew cavers there (it’s a small community) and we started to explore Carlsbad Caverns with these cavers. I started back to school at the Geology Department of the University of New Mexico in 1969. Three other UNM students and I decided to start working on the geology of Carlsbad.

inside carlsbad caverns

I was especially interested in the mineralogy of Carlsbad. I discovered a very waxy mineral there called endellite. It was known to form only in very low pH sulfuric acid solutions. So that made me realize that this cave was really different. The majority of caves around the world are called carbonic acid caves, which develop along the water table. But Carlsbad Caverns was formed very differently. It was a sulfuric acid cave. Carlsbad was the first big cave system to be identified by this mechanism, and now throughout the world, other caves like this have been identified. An active sulfuric acid cave has been found down in Tabasco, Mexico, for instance. But we did some of the pioneering work in Carlsbad.

Kathryn: I can’t imagine there were too many female geologists in the 1960s. What was it like? 

Carol: When I started out there were very few women in geology; in fact, when I became a student at UNM, I was the only woman in the department. I never felt discriminated against, but I was a special case because I was already married and had two sons, so I think no one expected me to ever do anything with my geology education. In fact, I never paid any attention to being a woman in a male-dominated field. I have always wanted to research subjects that interest me (including apologetics), and my attitude has been that if I became competent in these subjects I would be able to publish my research—which has proven true over many years.

Kathryn:  You went on from the Guadalupe Mountains to do some important work in the Grand Canyon. In fact, your discoveries upset the scientific consensus about the age and origin of the Canyon. How did you get started, and what exactly did you find? 

Carol: The way I got started in the Grand Canyon was I was working in other national parks, describing special types of mineral deposits (“speleothems”) called folia and mammillaries. Grand Canyon National Park asked if I would do similar work for them. So my husband and I and our youngest son, who was about 17 then, went down to a cave in the Grand Canyon – which is not easy to do in the canyon.

Once inside, I could see that the mammilaries and folia on the walls of the cave told the whole history of how it had formed: iron oxide layers were overlaid by spar layers, which were overlaid by mammillary layers, and so on. From my cave mineralogy work in other caves, I knew what those layers meant. The history of the Grand Canyon is in its caves!

If you think about it, you can’t date a hole directly, because all the material is gone. We can date the ages of the rock layers, but when it was carved is far more difficult to identify. I realized that by dating the mammillary layers in the cave we could date the formation of the canyon because this speleothem type forms at the water table.

At that time (12 years ago), most geologists believed the Grand Canyon was 6 million years old. But that is not the age of the Grand Canyon itself. It’s only the amount of time that the Colorado River has wound through the Grand Canyon. Our dates shed light on the formation of the Grand Canyon as a whole. We were approaching the origin of the Grand Canyon from an entirely different way than anyone else. Nobody had understood that karst (the study of caves) related to the canyon’s origin.

Eventually we showed that the Eastern and Western Grand Canyon had completely different incision rates, which meant the Eastern Grand Canyon was far younger than the Western Grand Canyon. We proposed that the Western Grand Canyon was very old and there wasn’t a connection between the Eastern and Western sides until about 6 million years ago.

When we published that article in Science (2008) you would think that we had committed heresy because all the Grand Canyon geologists knew that the Grand Canyon was only 6 million years old. My poor colleague Victor Polyak, the senior author and dating expert, was especially criticized by other geologists for saying that the Canyon was so old. But now it’s pretty much agreed on by almost all of the geologists working there that the first parts of the Grand Canyon formed 85 million years or so ago, and the Colorado River did not get to the western side of the Grand Canyon until about 6 million years ago.

Kathryn: What was your faith background? Were you raised in a Christian home? 

Carol: I was raised in a nominally Christian home where my mother took us to church and my father was an agnostic. I became a Christian through a 1966 Billy Graham television crusade and I still remain a Christian to this day.

My husband and I have been members of Heights Cumberland Presbyterian Church for almost 30 years, and I have been on the Missions Committee of our church for 20 years. Our granddaughter, her husband, and our 1 year-old great-grandson are missionaries in Zambia with the Overland Mission.

Kathryn: Have you ever experienced a sense of conflict between science and religion? 

Carol: Yes, I have, and I still feel a strong sense of conflict between views of Scripture that are popular in churches today and my knowledge as a scientist.

book cover: Monument to an Ancient EarthIn doing my Grand Canyon work, I saw the Young Earth Creationist (YEC) book Grand Canyon: Monument to Catastrophe on sale in the Grand Canyon book store. Later I saw YEC vans touring the South Rim in the summer. The guides taught that the mile-deep rock layers in the Grand Canyon were deposited in Noah’s flood in only one year’s time. These falsehoods proved too much to ignore. So, along with my friend and colleague Gregg Davidson (and nine other geologists/paleontologists) we wrote Grand Canyon: Monument to an Ancient Earth (Kregel, 2016), a primer for a lay audience on the geology of the Grand Canyon and the age of the Earth.

This same sense of conflict between how Scripture was being interpreted by the church and what I knew to be true in science was also the basis for writing my new apologetics book, A Worldview Approach to Science and Scripture (Kregel, 2019). I actually started this book 20 years ago as a result of a Sunday School class taught by a husband-and-wife missionary team who emphasized how missionaries must carefully consider worldview in their effort to present the gospel to unreached people groups.

book cover: A Worldview Approach to Science and ScriptureAt that time I had never heard of worldview, but came to understand that by “worldview” they meant “the basic way of interpreting things and events that pervade a culture so thoroughly that it becomes a culture’s concept of reality—what is good, what is important, what is sacred, what is real. It extends to perceptions of time and space, of happiness and well-being.”

That conceptual understanding clicked in my mind as also being potentially important for how to approach science and Scripture. It was from this point of view that I published a number of articles that form the basis for parts of my new book. The purpose of my Worldview book is two-fold: (1) to present solid science to the church, and (2) to make the “lost” world of Genesis real to laypeople (especially Christians) by publishing an all-color book featuring artwork, photos, maps, tables, and figures representing the world in which these ancient people lived.

Kathryn: What do you feel are the most exciting questions today when it comes to reconciling science and Scripture?

Carol: There are several, but I’ll pick just one that I cover in the book: how to think about Adam and Eve in light of the anthropological and archeological evidence for human origins.

My view is that Homo sapiens evolved as a group 200,000 years ago and Adam and Eve were a historical couple who lived around 5,500 B.C. This view is not easy for the church to accept, because of the widespread and strong insistence that Adam and Eve had to be the biological ancestors of the entire human race. This belief has led many to embrace the Progressive Creationist position, in which Adam and Eve were the very first Homo sapiens, who lived 50,000-200,000 years ago.

If the genealogies of Adam are to be believed at all (and I think they should be), Adam is not far removed in time from the Flood or the Table of Nations, and certainly not by tens to hundreds of thousands of years. The ancient-Adam scenario simply does not fit with the evidence specified by Genesis, which places Adam and Eve in the Neolithic period after the advent of farming and husbandry (Genesis 4:2) and not before. There is also the problem of “gaps” in the Genesis genealogies: can these gaps be stretched back tens to hundreds of thousands of years? Could the ark described in Genesis have been constructed by a Paleolithic or Mesolithic Noah using stone scraper and chopper tools? Furthermore, since it is known that narrative writing was not invented until about 2,500-2,000 B.C., these “gap” dates imply that the Genesis stories had to have been transmitted orally for an equivalently long time period. These difficulties are resolved by a worldview approach which suggests that Adam and Eve were real people, but not the parents of the whole human race. The genealogical line from Adam to Christ is Jewish history, not human history.

Kathryn: Fascinating. Thank you, Carol, for sharing your life and faith and career with us.  

Carol: You’re welcome. My career working in Carlsbad Caverns the Grand Canyon over so many years has been very exciting. Those are my two favorite places on planet Earth. And I hope many people, especially young people, will be helped by the book and see that science and Scripture really do fit together beautifully. Thank you.


About the Authors

  • Kathryn Applegate

    Kathryn Applegate

    Kathryn Applegate is Resources Editor at BioLogos. While working on her PhD in computational cell biology at The Scripps Research Institute (La Jolla, CA), she became passionate about building bridges between the church and the scientific community. In 2010, she joined the BioLogos staff where she has the privilege of writing, speaking, and working with a wide variety of scholars and educators to develop new science and faith resources. Kathryn co-edited with Jim Stump How I Changed My Mind About Evolution (InterVarsity Press, 2016). As Project Leader for BioLogos INTEGRATE, a curriculum supplement for high school biology, Kathryn is excited about the potential for BioLogos to equip parents and teachers to raise up the next generation of Christian students who approach science with wonder, curiosity, perseverance, and wisdom. Kathryn, her husband Brent, and their two young children live in Grand Rapids, Michigan. They love exploring the beaches and state parks of Michigan on the weekends, along with their beloved Cavapoo Teddy. They are part of a team working to plant a new church in the Presbyterian Church of America (PCA) denomination.
  • Carol Hill

    Carol Hill

    Carol Hill has worked as a geologist for more than 40 years as a researcher, consulting geologist, and teacher. Her specific areas of geological expertise are speleology (the study of caves), mineralogy, and environmental geology. She spent more than 25 years working in the Guadalupe Mountains of New Mexico and the last twenty years in the Grand Canyon. Her books include Cave Minerals of the World, Geology of Carlsbad Cavern, Geology of the Guadalupe Mountains, and Grand Canyon: Monument to an Ancient Earth. Most recently she published A Worldview Approach to Science and Scripture (Kregel, 2019). Hill’s work has also been featured on NOVA and National Geographic TV.
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