Profiles of Notable New Mexico Geologists

Carol Hill

Carol Ann Hill:

Born: August 8, 1940, Detroit, MI

Carol Hill grew up as a tomboy in San Diego California in the 1940s. Her strong character and ability to fit in with the boys ultimately shaped her life. Carol redefined the  mechanisms of cave formation in Carlsbad Caverns and parts of the Guadalupe Mountains, as well as is in the midst of developing a controversial new theory that reshapes the way we thought the Grand Canyon was formed.

Born Carol Ann Havens in Detroit, MI in 1940. The family moved to San Diego when Carol was 2 years old, due to her father’s career. Carol’s dad was a physicist who worked on plane design for Convair during World War II. Carol’s earliest memories come from that time.

“My earliest memory was of black outs during the war. My mom would put blankets on the windows to cover the light because they were worried the Japanese would bomb San Diego since that’s where the planes w ere being made. The MPs would come by to make sure the whole city was in a black out. The other thing I remember was my underpants kept falling off because we didn’t have elastic. They had paper coins to get on the trolley because all the metal and rubber was needed for tires. The day after the war ended we ALL lined up way down the street for one piece of bubble gum.”

Carol is the second child among four boys, five children in total. She jests that her poor mother technically had 5 boys, because she was such a tomboy. Pig tails and jeans was her usual attire, which is very fitting of the future geologist. The 1940’s was a different time for women. At this time practically all women became stay-at-home mothers and if a woman were to have a career there were about 4 different options available to them: a nurse, teacher, stewardess, or waitress. So when Carol enrolled at Berkley in 1958, she was planning to become a nurse, which she admits would have been a horrible fit for her since she didn’t even like to be nurse to her children when they were ill.

Carol moved to Ann Arbor and attended the University of Michigan when she married her husband Alan in 1960. Her student career was interrupted by the birth of their two sons, Larry and Roy in 1961 and 1966 respectively. Carol and her husband became avid cavers (spelunkers) while living in Ann Arbor. Exploring Mammoth Cave sparked Carol’s interest in geology, especially in how speleothems (cave formations) were deposited.

In 1967 Carol, Alan and their 2 small sons moved to Albuquerque. She enrolled part time at UNM in 1969.  She was the only woman for about a year in the Geology Department until Jayne Aubele, who is now Education Director with the NM Museum of Natural History, joined the department. The two of them were the only female members of the department for a few years; there were also no female professors at that time. Carol states that she has been lucky and the fact that she is a woman has never been an issue with her co-workers. Carol shies from special treatment as a woman and states “it is when people do not even notice that you are a woman anymore that is when we are really equal with men. If you’re set aside because you’re a woman then you’re still not equal.” It is Carol’s opinion that one should just do her job to the best of her ability. Sheoes not want to be favored or disfavored on the basis of being a woman. She thinks that the day when work will be judged by our work ethic and not by gender is closer than ever before. She has noticed that within the last 10-20 years, colleagues in particular do not treat her any different due to her gender.

Carol and Alan began exploring Carlsbad Cavern as soon as they arrived in Albuquerque in the fall of 1967, and Carol became intrigued by how different Carlsbad was from Mammoth Cave and other eastern caves she had visited. The majority of caves like Mammoth have long linear passageways at different levels, which represent the lowering of water tables. In Carlsbad, however, there is the “Big Room”—a room about the size of a football field. Inside the Big Room resides huge gypsum blocks whose origin was a mystery to all geologists who had studied the cave, including J Harlan Bretz, who had worked in the cave in the 1940’s. The cave minerals and speleothems in Carlsbad and the rest of the caves in the Guadalupe Mountains were also different from most other caves. No one could figure out why this cave was so different and how it had formed.

On one early cave trip into Carlsbad, Carol collected a peculiar, waxy mineral, which turned out to be endellite (hydrohalloysite). Endellite is a silicate mineral that has a sheet structure like mica. These sheets roll up like tubes under high acidic conditions. The presence of endellite suggested to Carol that this mineral had been formed under low-pH, sulfuric-acid conditions, and that began her interest in how the cave itself formed (its so-called “speleogenesis”). Sulfur isotope analysis of the gypsum blocks in the Big Room later confirmed that the caves had been formed by a sulfuric acid mechanism; a sample of this gypsum had a negative sulfur isotope value (-15 per mil), thus connecting the caverns with hydrocarbons in the Delaware Basin. Essentially hydrocarbons reacted with gypsum of the Castile Formation in the basin to form hydrogen sulfide, which then migrated into the Capitan reef.  This hydrogen sulfide reacted with oxygen to form sulfuric acid, which then dissolved the limestone and formed the huge cave passages. This reaction of sulfuric acid with limestone also formed gypsum, native sulfur, and endellite as by-products. It was the sulfur isotope values on the cave gypsum and sulfur that swayed Carol’s interest from mineralogy to understanding the cave’s speleogenesis.

Carol’s affiliation with the University of New Mexico began in 1969.  She had numerous transfer credits from Berkley and Michigan so she only needed to take a few classes to receive her bachelor’s degree in 1975. However, the only way to have all her credits transferred without having to retake many classes was to receive a Bachelors’ in University Studies (BUS) degree from UNM. Her one concern was getting into the Graduate program at UNM, but in order to guarantee acceptance, Carol only had to take a few required geology classes. During her tenure at UNM she wrote the first two editions of Cave Minerals and Cave Minerals of the World, which were partly based on her mineralogy work in Carlsbad Caverns and other caves of the Guadalupe Mountains. These books have been cited numerous times and have been used to inspire classroom tasks in which students learn about cave mineral formation. In 1978 Carol received her Master of Science in Geology. Her research topic was the origin of saltpeter in caves such as Mammoth, where saltpeter had been mined in the War of 1812.

In 1987 Carol published her book on the speleogenesis of the caverns in a book entitled Geology of Carlsbad Cavern and Other Caves in the Guadalupe Mountains, New Mexico and Texas with the New Mexico Bureau of Mines and Geology. Carol hoped to use this book as her PhD dissertation at UNM, but after taking all the required course work for a PhD degree, Carol learned that her published work on Carlsbad Caverns would not be accepted as a PhD dissertation. Since Carol would have had to spend nearly three more years doing new research for her dissertation, she never received the official title of PhD. Also, if Carol would have received her PhD at UNM, she would not have been able to work there as a professor, as UNM generally does not hire faculty who have received all their degrees from one institution. Having her family in Albuquerque, Carol was not looking to move either, so it was mutually beneficial that Carol received the education of a PhD candidate and was still able to later teach at UNM as a staff employee.

Carol is also known for her research in the Grand Canyon. Carol first visited a Grand Canyon cave in the early 1980s at the invitation of Grand Canyon National Park, who wanted her to look at a speleothem type called folia. This cave was difficult to access, and she had to rappel off the side of the canyon to get down to it (not unusual in the case of getting to Grand Canyon caves).  Coming out of the cave, she closely inspected the wall deposits in the entrance room, which consisted of iron oxides, spar and a speleothem type called mammillaries. Right then and there, Carol decided to return to the Grand Canyon someday. Carol realized that the whole history of the Grand Canyon could be tied up with these caves and cave deposits. Because erosion had carved the Grand Canyon, only these caves contained remnants of its former history of incision. However, over 10 years elapsed before Carol could return to the Grand Canyon, because she was working on her book Geology of the Delaware Basin, Guadalupe, Apache, and Glass Mountains, New Mexico and West Texas, published by the SEPM-Permian Basin Section in 1996. But she always had it mind that one day she would be back to study the caves and evolution of the Grand Canyon.

So in 1998 Carol finally returned to the Grand Canyon to begin her research there. She and colleague Victor Polyak first received a number of small grants for their preliminary work, and in 2007 they received a much larger National Science Foundation grant.  In 2008, Carol became an Adjunct professor at UNM, which is her position to this day. Mostly Carol identifies as a research professor, because what she is truly passionate about is research and field work. Victor Polyak, who has worked with Carol both in Carlsbad Cavern and during the whole time of her Grand Canyon research, is a dating expert at UNM at the Geochronology lab. In their Grand Canyon cave research, Victor and Carol found that most of the caves contained “mammillaries” – a speleothem type which can be uranium-lead dated and which denotes the position of the water table.  These deposits told Carol and Victor where the water table had resided in different parts of the Grand Canyon at different times, and which helped determine the age of the canyon’s incision. This data on Grand Canyon caves led Carol and Victor (along with Yemane Asmerom) to publish their Science article in 2008 entitled Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water-Table Type Speteothems. They concluded in this article that there had been an earlier, 17-6 million year old, western part to the Grand Canyon that had preceded the Colorado River.

Their Science paper was met with an uproar, because at that time everyone “knew” that the Grand Canyon/Colorado River was 6 million years old. While this date is partly accurate, it is only the most current age of most of the canyon’s incision. Carol has also worked with Wayne Ranney, who wrote Carving Grand Canyon: Evidence, theories and Mystery. Carol and Wayne have worked north of the Canyon and these findings prompted them to pose an even earlier canyon date than before—one going back in time to the Laramide (the Laramide is the time of uplift of the Colorado Plateau and the Kaibab arch). This research ultimately led Carol to propose that there were several different stages in the formation of the Grand Canyon, and that the Colorado River’s role in the canyon’s formation 6 million years ago occurred at the latest stage in the canyon’s evolution. The reason the river follows the route that it does today is due to the presence of these earlier canyons. Carol and Victor are trying to put together an early history of the Grand Canyon, including what uplifted when, and how and where these early canyons formed. Their most recent research substantiates that uplift of the southwestern Colorado Plateau started about 85 million years ago, and that at about 80 million years ago the Kaibab arch began to uplift and an early “proto-Grand Canyon” began to form on the west side of the uplifting Kaibab arch. This canyon connected with drainage coming from the Hualapai Plateau paleocanyons, and then flowed north toward Utah.

Carol has also posed a model of how the Colorado River could have crossed the Kaibab arch 6 million years ago. Not many people understand karst, a landscape formed from the dissolution of soluble rocks including limestone, dolomite and gypsum, and which is characterized by sinkholes, caves, and underground drainage systems. Using the new concept of an earlier Laramide “proto-Grand Canyon” and a 17-6 million year western Grand Canyon, Carol proposed that the Colorado River did not go over or cut through the Kaibab arch. Rather, it flowed under it via karst. This is a rather difficult concept for people to wrap their minds around, and it too has been highly scrutinized by Grand Canyon geologists. But such karst connections happen all around the world and are quite familiar to karst hydrologists.

Today, the Colorado River goes against dip in Marble Canyon then turns abruptly to the west and goes under the arch. The only plausible explanation for the Colorado’s present route through the canyon is if it formed in sections instead of forming all at once. Over time, sections of the canyon got reversed, which is not usual of river systems around the world. Most of the Grand Canyon that we see today was carved by the Colorado River over the last 6 million years, but before then a smaller, different set of canyons had already formed and these are the canyons that dictated the route the Colorado River was later to take. 

Carol and her fellow researchers have been critiqued for their work on the Grand Canyon. However, such a response is typical when a new idea completely challenges the prevailing paradigm. This response is similar to the one Carol received on her Carlsbad Cavern work, when Carol and her colleagues proposed that Guadalupe Mountain caves were formed mainly by sulfuric acid. Carol remembers the reaction of Frank Kottlowski, then Director of the New Mexico Bureau of Mines & Mineral Resources, when she proposed that the Bureau publish her work on Carlsbad Cavern: “That’s what we need around here – some new ideas.”

Carol feels that right now our knowledge of the evolution of the Grand Canyon is undergoing a renaissance. Many different researchers are proposing new and controversial theories, including the existence of earlier “proto-canyons.” One reason for so much controversy is that now there are new, sophisticated tools allowing researchers to perform better analyses. Every researcher is using a different method at a different location of the canyon, and so each one is coming up with a different story. This situation complicates attempts to assemble the pieces of the Grand Canyon puzzle. While the pieces may well fit together in the future, the geological community is currently unsure of how they will fit together.

Carol Hill has also conducted research in multiple National Parks and Monuments, has worked as an environmental geologist at Yucca Mountain and the WIPP site, and has published over 200 articles and 6 books, one of which is still in progress. Along with her mounds of articles, Carol has also been editor of 3 Symposiums. She has been featured in various PBS television specials, on NOVA, and on National Geographic TV. In 2006 the New Mexico Geological Society dedicated Guidebook #57 to her for her work in the Guadalupe Mountains and Delaware basin. She has also been recognized in numerous Who’s Who publications and received the 2002 National Speleological Society Science Award.

Publications (partial list; over 200 in all):


  1. Hill, C. A., 1976, Cave minerals: National Speleological Society, Huntsville, AL, 137 pp.
  2. Hill, C. A. and Forti, P., 1986, Cave minerals of the world: National Speleological Society, Huntsville, AL, 238p.
  3. Hill, C. A., 1987, Geology of Carlsbad Cavern and other caves in the Guadalupe Mountains, New Mexico and Texas: New Mexico Bureau of Mines and Mineral Resources, Bulletin 117, 150 p.
  4. Hill, C. A., 1996, Geology of the Delaware Basin, Guadalupe, Apache, and Glass Mountains, New Mexico and West Texas: Society of Economic Paleontologists and Mineralogists, Permian Basin Section, Publication no. 96-39, 480 p.
  5. Hill, C. A. and Forti, P., 1997, Cave minerals of the world, 2nd edition: National Spelological Soc., Huntsville, AL, 463 p.
  6. Hill, Carol A., et al., Grand Canyon: Monument to an Ancient Earth, in progress.


  1. Hill, C. A., 1981, ed., Cave Saltpeter Symposium: National Speleological Society Bulletin, v. 43, no. 4, 132 p. (+ author of 4 articles within symposium).
  2. Hill, C. A., 1999, ed., Kartchner Caverns Symposium: Journal of Cave and Karst Studies, v. 61, no. 2, 123 p. (+ author of 4 articles within symposium).
  3. Hill, C. A., 2000, ed., Caves of the Guadalupe Mountains Symposium: Journal of Cave and Karst Studies, v. 62, no. 2, 157 p. (+ author of 3 articles within symposium).


  1. Hill, C. A., Eberz, N., and Buecher, R. H., 2008, A karst connection model for Grand Canyon, Arizona, USA: Geomorphology, v. 95, p. 316-334
  2. Polyak, V., Hill, C., and Asmerom, Y., 2008, Age and evolution of the Grand Canyon revealed by U-Pb dating of water table-type speleothems: Science, v. 319, p. 1377-1380.
  3. Hill, C. A., and Ranney, W. D., 2008, A proposed Laramide proto-Grand Canyon: Geomorphology, v. 102, p. 482-495.
  4. Hill, C. A., and Polyak, V. J., 2010, Karst hydrology of Grand Canyon, Arizona, USA: Journal of Hydrology, v. 390, p. 169-181.


Earth Science, Mineralogy,  Speleogenesis


Guadalupe Mountains, Delaware Basin, National Parks, Carlsbad Caverns, Grand Canyon, proto-canyon, Southwestern New Mexico, Texas geology,  New Mexico Bureau of Geology and Mineral Resources