Student sleuths hone rock-solid reasoning skills

By Steven Schultz

Princeton NJ -- Gerta Keller acknowledges that the title of her course, "Sedimentology and Stratigraphy," is not particularly catchy.

"I didn't want students to sign up just for the fun parts," said the professor of geosciences.

Students in a course taught by geoscientist Gerta Keller take a field trip to Mexico  

Students in a course taught by geoscientist Gerta Keller take a field trip to Mexico where they look for geologic evidence of the mass extinction that killed the dinosaurs 65 million years ago. Here (from front) Keller helps dig a trench with undergraduates Steven Andrews and Maia Schweizer during a trip last spring.


Yes, fun parts. Keller's 300-level course is all about sedimentary rocks and the processes that formed them millions of years ago, but it also is about deciphering dramatic stories buried in those rocks, tracking down first-hand evidence with a pick and shovel and then stepping into the middle of a vehement international debate about the death of the dinosaurs.

The highlight of the course is a trip to Mexico where students dig up and analyze the fossilized debris from the impact of a giant meteorite that struck Earth 65 million years ago.

"It was really an amazing trip," said Yinan Wang, a junior who took the course last year. "It was amazing to see first-hand these sediment samples and these locations that I've only seen before in textbooks and on TV."

Along the way, students discover that Keller's interpretation of the geologic evidence differs sharply from the most commonly held view of the events of 65 million years ago. Keller disagrees with the theory that a single asteroid impact killed the dinosaurs and believes instead that a combination of events, including several impacts and a prolonged period of volcanic activity, caused the mass extinction.

For Keller, this difference of opinion is an opportunity not to promote her view but to expose students to scientific debate and encourage them to develop and defend their own hypotheses.

"She showed us her idea, but didn't force it on us," said junior Richard Lease. "She said: 'This is their interpretation; here is what I think; and now I want to hear what you think.'"

Senior Steven Andrews said Keller's emphasis on hands-on learning and individual interpretation made the course one of the best he has ever taken. The wide range of possible viewpoints, based on the same evidence, quickly became apparent, Andrews wrote in an e-mail message. "Although some interpretations are more plausible than others, often it seemed my peers and I would come to accept the voice of the classmate who happened to be the most outspoken at the moment."

Keller's ambitions for the course go beyond asking the students to debate particular episodes in Earth's history. She wants them to develop a general ability to look at rock formations and answer a host of questions: When was it formed? Did it come from an ocean? How deep was it? Why does it have its chemical composition? What organisms were present? What was happen- ing in the environment at the time this rock was formed?

"They can just about create the whole story," she said. "And they enjoy that a lot."

Related article
Dinosaur dust-up: Princeton paleontologist produces evidence for new theory on extinction


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