New research from Montana State highlights subsurface impact of Yellowstone earthquakes

BOZEMAN – In Yellowstone National Park, earthquakes are an everyday occurrence whether humans feel them or not. In fact, data shows that as many as 3,000 quakes of various magnitudes occur in the park each year.

That regularity makes Yellowstone a perfect place to study the many impacts of seismic activity on ecosystems, said Montana State University professor Eric Boyd. In a new paper published this week in the journal PNAS Nexus, Boyd explores how Yellowstone’s earthquakes impact some of the planet’s earliest lifeforms, and what such lifeforms could tell us about life on other planets.

“I think it's one of the more significant findings that I have ever been a part of,” said Boyd, who has conducted research in Yellowstone for more than two decades as part of MSU’s Department of Microbiology and Cell Biology. “There are hypotheses that microbial life originated in the subsurface 3.8 billion years ago. These microbes would have been dependent on chemical forms of energy stored in minerals. As the microbes consumed this energy, the minerals would become depleted, and there’s simply no way such ecosystems could persist without a mechanism to replenish them.”

By fracturing and shearing rock, earthquakes allow fresh, reactive minerals to be exposed, Boyd said. While earthquakes are common nearly everywhere, they are particularly frequent in a volcanically active place like Yellowstone, making it a perfect location for the research.

“Eric’s investigation into how seismic activity shapes microbial communities in the Yellowstone ecosystem is yet another excellent example of his groundbreaking research exploring how microbial life persists and evolves in extreme environments,” said Jovanka Voyich, head of the Department of Microbiology and Cell Biology, which is housed in MSU’s College of Agriculture. “The fact that MSU undergraduate and graduate students can take courses and receive mentorship from one of the world’s most prestigious geobiologists is a remarkable educational opportunity.”

Boyd is the lead author on the new paper, titled “Seismic Shifts in the Geochemical and Microbial Composition of a Yellowstone Aquifer.” The work brought together extensive data on the underground systems of the national park, including measurements of thousands of earthquakes and explorations of the microbes that live beneath the surface, along with the chemicals that they need to survive. Early Earth, Boyd said, didn’t have an atmosphere like the one it has today, so radiation levels on the surface would have made it uninhabitable. For that reason, early life most likely originated underground. But how did it survive there?

That question has driven much of Boyd’s research, including this latest project, which was funded by a $1 million grant from the W.M. Keck Foundation awarded in 2020. Microbes underground don’t use air and sunlight to survive like plants, animals and people do; instead, they consume and process elements from the rocks around them to reproduce and evolve. Drawing those elements out of the surrounding rocky environment requires an external driver. In Boyd’s newest discovery, that driver is earthquakes.

Because a substantial portion – as much as half, by some estimates – of Earth’s microbial biomass resides underground, Boyd said understanding how that life has sustained itself can give insights into not only how that life has evolved, but also the potential for where and how it could reside on other planets.

“If you perturb a system, there will be a response. If you want to understand how our systems work, you need to understand those responses,” he said. “So much of the biomass on Earth is microbial, and if you eliminated that, there would be no higher forms of life. It’s as simple as understanding the food that sustains the microbes that sustain you.”

While conducting research for the project, Boyd was at one point taking real-time measurements of the microbes present in a deep well near Yellowstone Lake, noticing significantly higher levels of sulfur gases than he’d previously measured. When he later looked at the seismic logs for the same time, he realized the sampling had overlapped with the onset of an earthquake swarm, in which several small quakes converge over the same period.

Shaking and fracturing the rocks beneath, the seismic activity altered the supply of elements and nutrients the microbes need to thrive, setting off a chain reaction that resulted in a bloom that changed the microbial composition in the aquifer. For a period of several months, the microbes had much more of the food they needed to grow and reproduce. As the earthquake swarm ceased, the concentration of microbes and elements returned to previous levels.

Deepening understanding of these systems, Boyd said, has been the challenge and opportunity of his career. As it has been for decades, MSU remains a perfect place to study the fundamentals of life through its proximity to Yellowstone’s unique landscapes.

“Every single ecosystem on Earth is ultimately supported by microbes,” Boyd said. “They are the base of all ecosystems as moderators of the geochemical cycles that sustain plant, animal and human health. If half of that base that sustains all life on Earth is in the subsurface, then you better understand how that microbial base has sustained itself.”

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This story is available on the Web at: http://www.montana.edu/news/24951