Mark Cloos: Professor Emeritus

December 5, 2022

By Anton Caputo

It has been just over 40 years since Mark Cloos stepped on the campus at The University of Texas at Austin as a young assistant professor. Raised in the northern suburbs of Chicago, he chose UT over other offers because he saw the potential, particularly in the remarkable crop of young assistant professors that he would soon be joining.

“Bill Carlson was here. Sharon Mosher was here. The petrology and sedimentology groups were in strong support of the structural geology and tectonics program. We had the microprobe, X-ray diffraction, thin section lab — all the tools that I wanted,” Cloos said. “There was a lot of energy. The place had a hum, and the senior faculty, John Maxwell and Bill Muehlberger, were not just supportive, they said, ‘Take us to the future.’”

During the next four decades, Cloos would do as much as anyone to ensure the program kept on humming. He taught structural geology to generations of UT students — more than 2,300 in all, with some of those students being the children of students he taught in the 1980s. He was associate chair of the Department of Geological Sciences from 1986 to 1989 and chair from 1996 to 2000. He made significant scientific breakthroughs and carved out a near-legendary status with his hand specimen labs and field trips that helped students develop a holistic understanding of the forces that shape the planet.

More than 700 students attended his whirlwind Oklahoma field trip to the Arbuckle and Ouachita mountains.

As an educator, he has a rare way of pushing students to think and work through a problem, said Jackson School of Geosciences Professor Richard Ketcham. He said Cloos could be intimidating because of his depth of knowledge, but he gave tremendous time, energy and encouragement to his students. Ketcham should know; he was a student of Cloos’ before becoming a colleague.

“If you’re resting on fuzzy logic, gray literature or catch phrases instead of real thinking, he would call you on it,” Ketcham said. “It was challenging, but you always knew he was on your side. He took some really raw material and made some very, very good scientists.”

Now, after years of working with students in the classroom and field, Cloos, the Getty Oil Company Centennial Chair in Geological Sciences, has retired from the faculty and joined the ranks of professor emeriti.

During his career he lived the highs and the lows of UT geosciences — literally. He was an assistant professor in 1983 when undergraduate enrollment peaked at 825 students — with only 24 faculty members to teach them — as a generation rushed to get into the booming oil and gas industry. Both his stints as department chair and associate chair were when the price of oil plummeted and the department had to focus on nonmajor classes to justify teaching assistant budgets and to attract students. A silver lining from the 1980s low was the creation of the wildly popular class on the geology of national parks, which Cloos co-created and taught with Professor Gary Kocurek. The course has since morphed into a class called Earth, Wind and Fire.

Cloos was also one of the early contacts with Geology Foundation member Jack Jackson, helping secure the original oral agreement to fund an addition to the geology building. That was the beginning of the philanthropic relationship that eventually became the endowment that launched the Jackson School of Geosciences.

Cloos received his undergraduate degree from the University of Illinois Urbana-Champaign. As a doctoral student at the University of California, Los Angeles, he worked with legendary Professor Gary Ernst as he developed the model of how backflow up subduction shear zones can explain the origin of shale-matrix mélange in accretionary prisms.

As he was completing his degree, Cloos began to collaborate with another UCLA faculty member, Ronald Shreve. They expanded the flow mélange concept to a general model for subduction shear zones, which they termed “subduction channels.”

“I think we were well ahead of our time in terms of that mode of thinking, but now many others are on board as the term subduction channel is widely used,” Cloos said.

In 1988, Cloos traveled to Papa New Guinea as part of a National Science Foundation-sponsored field trip to investigate the results of arc-continent collisional tectonism in the region. During that time, he connected with former student JR Moffett in neighboring Indonesia, and the two began a project in 1989 on the geology of Grasberg orebody that continues to this day. The orebody proved to be a supergiant copper deposit with a significant byproduct of gold. What began as a five-year project with a team of doctoral students morphed into a long-term venture co-led by Jackson School Professor Emeritus Richard Kyle that produced 18 theses and dissertations supervised by Cloos and brought about 130 undergraduate student researchers into the fold. Cloos’ army of students also took on many projects in California on subduction and transform margin geology. Many of those students chose their thesis topics by participating in one of his California field trips, with Cloos taking more than 300 UT students to see the wonders of California geology over the years.

Early in his career, Cloos taught sections of field camp in Taos and Durango when about 130 students took the summer course. Since 2005, he taught Introduction to Field Geology, a class for nonmajors that he inherited from Professor Emeritus Leon Long. But Cloos is probably best known for bringing students on his optional field trips to California and Oklahoma, which have been Jackson School fixtures for decades. It is during these trips that he says “the lights come on” for many students as they explore outcrops and then hear the geological stories behind what they are seeing.

One such student was Andrew Quarles, who earned a doctoral degree under Cloos’ supervision in 1996. He remembers not knowing what to think of Cloos at first, with his “endless intense questions” and encyclopedic knowledge. But by the time Quarles graduated, Cloos had such an impact on his life that Quarles and his wife, Stacy, have now started an endowed graduate fellowship in Cloos’ honor.

“Beneath that intensity was an educator dedicated to sharing and developing his students,” said Quarles. “Whether you were his Ph.D. student, a student in one of his many undergraduate or graduate classes, or a part-time research assistant, you knew you were receiving remarkable and dedicated attention and encouragement.”

Ketcham, who has educated scores of students himself, sums up Cloos’ impact simply.

“By the end of my first semester, I decided that Mark was the kind of scientist I would aspire to be,” he said.