Between the flows
Gerta Keller’s controversial dinosaur-extinction theory
You can tell a lot about Gerta Keller’s controversial ideas by the pictures on her office wall. In one, a Tyrannosaurus rex writhes in agony as magma bubbles from volcanic fissures. In another, single-celled sea creatures called foraminifera stand out against a black background like lumpy popcorn.
For Keller, a geologist at Princeton University, the foraminifera hold clues to a major paleontological mystery — what killed the dinosaurs 65 million years ago. Keller, 66, is challenging the most popular hypothesis: a giant asteroid landed in the Gulf of Mexico and wreaked havoc on Earth’s atmospheric balance.
“Let’s face it, that impact was not big enough to cause a mass extinction,” says Keller.
She and some like-minded colleagues think that the extinction at the end of the Cretaceous Period was caused by a different catastrophe — massive volcanic eruptions in India called the Deccan Traps.
Keller’s theories are highly controversial. “Hardly anybody now considers Deccan volcanism as a major factor in the extinction,” says Brian Huber, a paleobiologist at the Smithsonian Institution. Despite this resistance, Keller continues to research and advocate her alternate theory.
Keller’s Swiss origins are evident in her soft accent and the white edelweiss on her collar. Born in Lichtenstein, Keller was the sixth of 12 children. She grew up on a dairy farm in Salez, Switerzland, a small town across the river from Lichtenstein. Keller’s childhood was fraught with financial uncertainty. “Every six months our farm was on the auction block,” she says.
Keller did not learn science or math in school — those subjects were only for boys. “Instead of math we had to do sock mending, cooking, [and] cleaning,” she says. But Keller showed early signs of rebellion against conventional views, and decided she wanted to be a doctor. Dismayed by her choice, the school contacted a psychologist to administer an inkblot test and set her straight.
But Keller did not give up easily on her ambitions. “If I can’t be a doctor, I’ll become a fashion designer,” she told the psychologist.
So at 14, she became a dressmaker’s apprentice, but the salary did not even cover her daily train fare. “It was basically slave labor,” Keller says. She then worked as a dressmaker for a Parisian designer, but switched to waitressing to earn more money. Working 18 hours days, she saved enough to travel frequently, visiting England, Spain, North Africa, the Middle East, Asia, and Australia.
Her travels ended for a while when she enrolled at San Francisco State University in 1968. Keller initially wanted to study anthropology, but chose geology when a professor told her that geology would give her many opportunities to travel. “He said… there are rocks everywhere,” she recalls.
Keller received her PhD in geology and paleontology from Stanford University. Then her husband was offered a position at Princeton University, but Keller was reluctant to move, remembering the cold Swiss winters. But her husband promised her a house where each of her pet tortoises had a room. “Of course he didn’t hold to it, I had a dozen at the time,” she says.
Keller became interested in the Cretaceous extinction soon after the discovery of the Chixulub crater in the Gulf of Mexico. The crater was located in 1980, around the time that the physicist Louis Alvarez unveiled his theory that an asteroid impact caused the extinction of the dinosaurs. A decade later it was confirmed that Chicxulub was an impact crater from the end of the Cretaceous Period, and other scientists began looking for evidence linking the impact to the extinction. Keller was intrigued, but says she did not want to “jump on that bandwagon.”
After waiting five years for the dust to settle, Keller began studying Chicxulub. Unlike many other scientists, she thinks that the Chicxulub asteroid was too small to cause a mass extinction, and that it struck at the wrong time — about 300,000 years too early.
But Keller needed an alternative explanation, and she found it on the opposite side of the globe. The Deccan Traps were erupting around the time of the extinction, sending lava flows over almost half of India and the Bay of Bengal.
These lava flows, and the marine sediments trapped between them, are now two miles below the surface. To study them, Keller traveled to India to retrieve rock cores drilled by India’s National Oil and Gas Corporation.
Keller noticed that the number of foraminifera species in the marine sediments decreased drastically in between eruptions, indicating that Earth was increasingly inhospitable to life. A decline in foraminifera and other geologic indicators suggest that the Deccan eruptions caused catastrophic global changes and large-scale extinctions.
Though Keller thinks volcanism was the main cause, she acknowledges that asteroid impacts might have played a part. “That’s the thing that is kind of weird,” says Brian Gertsch, a geologist at the Massachusetts Institute of Technology and a colleague of Keller’s. “She is trying to include what impact people are basically saying, but they still get mad.”
Not everyone agrees with Keller, and the subsequent debates have turned personal. Gertsch recalls stories of heated arguments at conferences, including people publically yelling at Keller.
Huber, who also studies foraminifera, disagrees with Keller’s analysis of Chicxulub. Like many scientists, he believes the asteroid directly caused the mass extinctions. “The cause and effect are very clear,” he says. While Huber agrees that Deccan volcanism did affect climate, he sees no evidence that the eruptions significantly affected foraminifera populations world-wide.
Even if Keller is wrong about Chicxulub, volcanism could have played a role in the extinction. Paul Renne, a geologist at University of California at Berkeley, notes that volcanism has contributed to other mass extinctions in Earth’s history. “It’s getting hard to believe that they didn’t both contribute,” he says.
Despite the debate, Keller says she ignores her critics. “I don’t try to convince those who can’t be convinced,” she says. She attributes the popularity of the Chicxulub hypothesis to its cinematic appeal. “It’s very imaginative, it’s very sexy,” she says.
Keller faces the controversy surrounding her theories with the characteristic independence she showed in her childhood. As Gertsch ironically observes, “she always finds a way to make an impact.”