After 44 years of teaching at the University, geology professor Robert Sloan will deliver his last lecture today.
“Some people talk about dinosaurs; some people are dinosaurs,” said Sloan, who has taught longer than any professor in the department’s 125-year history.
Sloan teaches vertebrate paleontology and historical geology in the Institute of Technology. He estimates that he has taught the introductory-level historical geology class more than 150 times to some 18,000 students since he began teaching during the Eisenhower administration.
“The names of the courses have stayed the same, but the content changes every quarter. I’ve never given the same course twice.”
That’s an understatement, in the view of one of Sloan’s former students.
“I doubt he ever gave the same five minutes twice,” said Robert Zink, a professor of ecology at the University who took Sloan’s classes as a zoology student some 25 years ago.
Sloan lectures without notes and often slides into unanticipated tangents.
“There’s a huge supercomputer bank in his head, and he steps into some part and turns it on,” Zink said.
Sloan’s single-minded focus on ancient fossils sometimes leads to a neglect of more mundane issues.
“He would perennially miss the start of class by 10 or 15 minutes and would perennially go past the end of class by 10 or 15 minutes,” Zink said. “As he walked in the door, he began spewing facts and information that perfectly picked up from where he left off the last time. I think he’ll be sorely missed. He’s quite a persona.”
Sloan dropped out of high school at the end of his sophomore year in 1946 and immediately entered the University of Chicago.
“I had as my peer group returning World War II veterans,” he said. “I recommend it highly: Abandon the last two years of high school, and go on to important things!”
Sloan joined the National Guard because he worried that he would be drafted and sent to fight in Korea.
“I wanted to make certain that I had more than just basic training if I went,” he said.
The Korean War ended in 1953, immediately after Sloan received his Ph.D. in geology from the University of Chicago at the age of 23. He was then hired as an instructor at the University.
Sloan said the biggest change in geology over the past four decades was the acceptance of the theory of plate tectonics as a model to explain mountain building, earthquakes, volcanos and other geological phenomena. Plate tectonics holds that giant plates of rock move the continents and oceans, forming many significant geological features.
“The whole United States was absolutely opposed to continental drift,” Sloan said. Opinion among U.S. geologists completely reversed during a six-month period in 1960.
Sloan’s research accomplishments include the discovery of the oldest fossil of a hoofed animal as well as the oldest fossil of a primate.
The primate fossil, called Purgatorius ceratops, was found on Purgatory Hill in Montana. For the oldest specimen, only a single tooth was found.
“We named it Purgatory Hill because it’s above Hell’s Creek,” Sloan said. The fossil is about 65 million years old.
Sloan also uncovered the only dinosaur fossil ever found in Minnesota, a bone from a duck-billed dinosaur.
“It was a crummy dinosaur tail bone, the least important fossil I ever found,” Sloan said. “It came from the Oak Clay Pit in Springfield, Minnesota, which is where all the brick on the Minneapolis campus comes from.”
The extinction of the dinosaurs has been a research focus for Sloan for the past 30 years.
He discounts the view that an asteroid was responsible for the extinction of the dinosaurs. Twenty-two of North America’s 34 known species of dinosaurs were already extinct before an asteroid struck at the end of the Cretaceous period 65 million years ago.
“It turns out that there were about five things going wrong at the same time, and you can’t pick any one of them as the sole reason for dinosaur extinction,” he said.
One major factor was the instability of the sea level, which rose and fell by as much as 200 feet.
“A rise in sea level would reduce the number of kinds of dinosaurs possible because it would reduce the area,” Sloan said. “A drop in sea level would permit mammals and other dinosaur competitors to migrate in from Asia.”
Sloan also emphasizes the decline in oxygen levels that occurred at this time. The concentration of oxygen in the late Cretaceous dropped from 35 percent to 27 percent.
“Late Cretaceous dinosaurs lived in an oxygen tent,” Sloan said. “The oxygen was being used up in weathering of rock and was not being replaced by photosynthesis as fast as it was being used up.”
Sloan said that he has not yet seen “The Lost World,” the sequel to the 1993 dinosaur movie “Jurassic Park.” However, he said he did notice several errors in the original movie.
“The first thing is, it shouldn’t be ‘Jurassic Park,'” he said. “It should be ‘Cretaceous Park.’ All of the dinosaurs they show are from the Cretaceous period.”
The Cretaceous began 144 million years ago, just after the Jurassic.
Cretaceous dinosaurs would have had a hard time adjusting to today’s atmosphere, which is only 21 percent oxygen.
“They would be hacking and wheezing, so the poor tyrannosaur would not be able to chase the attorney,” Sloan said.
After retirement, Sloan plans to move to Winona, where his wife Sally works as a professor of mathematics. He said he intends to study seashell fossils in southeastern Minnesota from the Ordovician period, which began roughly 500 million years ago.