Geologist Looks to Earth’s Past for Hints of Earth’s Future
By Justine Hofherr
BU News Service
In his quest to understand earth’s history, Professor Sam Bowring has traveled to Siberia, Poland, India and China. He has been chased by a black bear for four hours through the Northwest Territories of Canada, eventually ridding himself of the beast by shooting a flare gun into its eye. He has stared into the eyes of a mountain lion all night long in the scrub brush desert of New Mexico, wielding only a small knife and hammer, eventually dozing off as his campfire cooled and awaking to the sound of the lion’s screams in the distance.
Bowring is, first and foremost, a geologist—and he has a mystery to solve.
The adventures the Indiana Jones of geology encounters, whether he’s gathering rocks in South Korea or geomapping in the Cascade Mountains of Washington, are a bonus.
“I’m interested in the origin and evolution of the Earth’s crust,” Bowring said, sitting at his office desk in MIT’s Green Building, the tallest building on the Cambridge, Mass., campus.
Bowring, with bright sapphire eyes and a thick gray beard, has a quiet, serious demeanor as he discusses his work. Behind him, three metal bookshelves span the length of the room. The shelves are full, and every single title is about geology.
“Work is my hobby,” Bowring said, pausing to adjust the collar of his gray button-down shirt. “I like being outdoors and hiking, but I think about science all the time.”
For the past 20 years, Bowring has spent every day of his life trying to understand precisely when–and why 252 million years ago, at the end of the Permian Period, 96 percent of earth’s life disappeared.
Bowring and his colleagues traveled to a set of hills in China where there are rocks from the late Permian, early Triassic period. These rocks contain layers of fossils that show the scientists when certain species went extinct. Not only are there fossils preserved in these rocks, but there is also volcanic ash.
It is a mineral—zircon—in the volcanic ash that proves most useful to Bowring.
Bowring separates zircon, a brownish translucent mineral, from the ash because it has a special property.
When zircon forms in the newly spewed ash, the element uranium fits into the crystal structure quite nicely, he said. But lead does not—it’s radiogenic, meaning, it’s produced by radioactive decay.
“So the day that crystal forms, you have a clock,” Bowring said. “That clock is based on the decay rate of uranium to lead. By measuring that ratio, we can calculate the age of that ash quite precisely.” Bowring smiles as he makes this point.
Bowring thinks that by narrowing the time frame of this mass extinction, he and his colleagues could shed light on what factors might have caused it, possibly exposing parallels between what the environment looked like then, and now.
“Studying this is interesting because this is the largest extinction that animal life has seen on this planet,” Bowring said. “As we push to shorter and shorter time scales, it starts to be relevant to our own existence on this planet and what we’re doing to it.”
Recently, Bowring and his colleagues had a breakthrough thanks to increased precision in measuring rocks—they published a report in January for the Proceedings of the National Academy of Sciences definitively stating that the mass extinction took less than 60,000 years.
While 60,000 years might seem like an incredibly long time to humans, in geology, this is a blink of an eye and means the extinction took place much more rapidly than previously thought.
Bowring describes this knowledge as “sobering” because the scientists have found a clue—spikes in carbon dioxide—that correlates with this narrowed time frame.
“When you look at the fossil record, you see fossils begin to disappear based on physiology and their ability to deal with high CO2 emissions,” Bowring said.
Animals, the ones who “sat in the mud and filtered water,” were the first to go, he said. They just couldn’t handle the accelerated rate of CO2 emissions. The last animals to disappear from the fossil record were the more active organisms.
Another clue Bowring has noted is that right after the extinction, animals couldn’t precipitate shells made from calcium carbonate very easily.
“There’s a dearth of shells in the fossil record,” Bowring said.
A simple way to inhibit the precipitation of calcium carbonate is to drop the pH, or acidity, of seawater.
“Today, people are very concerned that the pH of sea water has dropped about a tenth because of high carbon emissions,” he said.
Though Bowring and other scientists have thus determined that the mass extinction correlates with high CO2 levels and low pH levels in the ocean, they still struggle to understand precisely what could have caused this.
They do know that mammoth volcanoes in Siberia called the Siberian Traps were burping lava around this time for about a million years, spewing between three and 10 million cubic kilometers of scorching lava over the earth. Between three to five million cubic kilometers is enough to put a kilometer of lava over entire the entire United States—so that’s a lot.
While volcanic eruptions, even minor ones, can be responsible for sharp spikes in CO2 emissions, Bowring is not satisfied placing blame solely on the Siberian Traps.
“Timing is crucial,” he said. “We know that the Siberian Traps overlap with the extinction, but their eruption took place over a million years. Why, then, did the extinction take only tens of thousands of years?”
This question continues to puzzle Bowring and other scientists—perhaps the extinction was the result of a combination of factors, and the eruption of the Siberian Traps pushed the majority of life’s adaptation capabilities over the edge. But the lack of certainty doesn’t mean they won’t stop trying to narrow the time frame for further clues.
After all, there are no “absolutes” in science, Bowring said.
“I suspect that in the next year we will make that time frame much smaller,” he said.
Regardless of finding the exact cause of the extinction, Bowring believes the raised levels of CO2 from the end of the Permian Period reflect Earth’s current state, but the levels have been rising at a much accelerated pace.
The driving force of climate change, the high emission of CO2 through the burning of fossil fuels, has taken a phenomenon that occurred over tens of thousands of years and has put it on a decadal time scale.
By the mid 21st century, the magnitudes of projected changes for global temperature shift will be substantially affected by the choice of emissions scenario, according to the 2013 Intergovernmental Panel on Climate Change. The panel also noted that it is “extremely likely” (greater than 95 percent confidence) that most warming between 1951 and 2010 was human-caused.
This information is depressing, Bowring said, but what’s more depressing is that humans aren’t prepared to change their actions accordingly. Young people are taught that the only successful economies are ones that grow, and they grow at the expense of burning fossil fuels, a quick energy fix that is unsustainable.
This is largely because people only think about climate change on a very small time scale—“How can you expect people to make intelligent decisions about climate change when half the population thinks Earth is less than 10,000 years old?” he said.
In this vein, Bowring thinks a start to solving the problem involves better Earth science education at high schools and universities.
Many Earth science programs have been cut from course curriculum at public schools—even in Massachusetts, a state at the forefront of cutting-edge scientific research, he said.
Furthermore, taxpayers in 14 states will bankroll nearly $1 billion this year in tuition for private schools, many of which are religious and teach that the Earth is less than 10,000 years old, according to Politico.
While public schools cannot teach creationism or intelligent design, private schools receiving public subsidies can and still do. This is fundamentally at odds with students understanding the history of Earth’s environment, and therefore prevents them from understanding the challenges faced in our current environment, Bowring said.
“Anyone who will listen about geologic time and the importance of understanding evolutionary history and applying those lessons to the hard future, that’s really important,” Bowring said. “We don’t do enough of it.”
Bowring said when he thinks about his life’s accomplishments, he’s most proud of the students he has produced who are interested in solving similar problems. He can tick off the names of five students who are now teaching geochronology at various universities around the United States.
“Your scientific achievements—they are just flashes in the pan,” Bowring said. “You’ll get a newspaper article published, but 30 years from now, no one will remember that.”
Julia Baldwin, an assistant professor at the University of Montana, is a former student of Bowring. She took his geochemistry class and he encouraged her to get involved with geochronology research in Saskatchewan, a prairie province in Canada.
When you’re in the field with Bowring, Baldwin said in a phone interview, you collect ten times more rocks than any other day. He encourages students to pull out their giant rock hammers to hack away at rocks, filling their backpacks till they weigh 50 pounds, she said with a laugh.
“He’d say, ‘You might never see this rock again!’” Baldwin said in a phone interview. “He’s just so excited about everything you see.”
Besides his passion for science, she said she was struck by how committed he was to his students.
Completely devoted to undergraduate education, Bowring goes out of his way to lead field trips to Yellowstone National Park before classes start, Baldwin said. That’s how he gets students so excited about geology, she said—he actually gets them outdoors looking at it.
“He puts a lot of responsibility in students’ hands,” Baldwin said. “He first gives you the knowledge then says, ‘Go do great things with this.’ But he doesn’t take credit for it—he just doesn’t have an ego like that.”
Like Bowring, Baldwin also thinks a greater emphasis on earth science education needs to exist, from kindergarten to college.
Students need an understanding of deep time and what it means in order to evaluate the present day climate problems, Baldwin said.
“Students should make decisions with a ‘scientific citizen’ mindset, and be able to evaluate basic science and climate change within the context of geologic time,” she said. “The more they can come into contact with this knowledge, the better.”
Like Baldwin, Professor Ethan Baxter at Boston University said Bowring is a “remarkable” individual, imparting critical earth Science knowledge to his students.
Besides citing him as “the best zircon geochronologist in the world,” Baxter calls Bowring “a good doobie in general.”
Baxter is also a geochronologist, studying the formation of earth’s crust. Instead of zircon, however, Baxter uses garnets to date time.
Fingering a garnet that sits atop his office desk in the Stone science building on BU’s campus, Baxter explains the magic of unlocking the stories that each mineral holds about earth processes—processes related to the past and present.
“Anyone that studies earth history is always thinking about how can we take our information that we have from the past over those tens, to hundreds of thousands, to millions of years time scale, and then apply that to what’s happening today on the decadal time scale,” Baxter said.
Similar to Bowring’s findings in the Siberian Traps, Baxter has found evidence that links spurts of garnet growth around the world with ancient increases in CO2 emissions.
Though he acknowledges that there is still no “smoking gun” in relation to what caused the mass extinction in the Permian Period, Baxter said Bowring’s efforts to narrow the time frame have shown, increasingly, that there are great similarities between the environment then and now.
“Sam’s work with the methods they are using for zircon, he’s reached a resolution in time, which transcends everything we’ve ever dreamed of,” Baxter said.
But despite great leaps in scientific discovery, education lags behind, he said.
When you’re talking about pressing matters like climate change, resource depletion, water quality, sea level rise and the melting of the Arctic ice cap, Baxter said, you notice that comprehension starts with having a basic understanding of earth science.
“A lot of states don’t include it anymore,” Baxter said of earth science education. “It’s a real shame. I don’t think people have a disinterest—they have a lack of awareness.”