A Snapshot of an Eruption

What Volcanic Crystals Tell Us About Magma Chambers

Yellowstone hot spring
Working in the lab of Professor of Earth and Planetary Sciences Kari Cooper, doctoral student Anjelica Guerrier analyzes volcanic crystals from old eruptions to learn about the state of magma chambers, including the magma chamber of the Yellowstone supervolcano. (Photo by Simon Hurry on Unsplash)

Around 170,000 years ago, the Yellowstone Caldera — a supervolcano — produced a series of small eruptions in frequent pulses lasting roughly 100,000 years. Remnants from those eruptions can be found on the Earth’s surface today as volcanic rock. And those rocks contain critical clues about the interior of the supervolcano. 

“The rocks left behind from eruptions can provide information about what the magma chamber looked like moments before eruption,” said Anjelica Guerrier, a second-year Ph.D. student in the Department of Earth and Planetary Sciences. “We’re taking advantage of that snapshot that’s been erupted.” 

Guerrier works in the lab of Kari Cooper, a geochemist studying the “black box” of volcanoes, magma chambers. Through isotopic analysis of erupted volcanic crystals, Guerrier and Cooper are gaining insights into the volcanic states preceding eruptions. The research could inform what Guerrier refers to as our “quest for predictability in the face of nature’s awe-inspiring power.”

“This research journey isn't just about uncovering geological insights; it can help pave the way for better hazard prevention and mitigation strategies,” Guerrier said. 

Volcanic encounters

Anjelica Guerrier
(Courtesy of Anjelica Guerrier)

It’s hard to not be struck with awe by the sheer magnitude of volcanoes. They quite literally move the Earth. 

While pursuing a master’s degree in geosciences from Georgia State University, Guerrier traveled to Costa Rica to study the history of volcanoes with overlapping eruptions in the region. 

“The weather and vegetation made studying volcanoes there challenging,” Guerrier recalled. “I hiked miles in wet shoes and got bit by a million mosquitos, but I had such a great time collecting rock samples.”

Despite the difficulty of the trip, Guerrier was hooked on volcanology. But life as a professional geologist after Georgia State University wasn’t what Guerrier thought it was going to be. She ended up in an environmental remediation position. The cubicle office, the trips to gas stations and dry cleaners were a far cry away from the Costa Rican volcanoes. 

She wanted to return to volcanology. But while Guerrier was applying to Ph.D. programs, the COVID-19 pandemic hit, putting a pause on her academic pursuits. She bided her time and got a job working at a brewery. Eventually, she returned to the application pool. 

“I knew I wanted to do something that pushed the boundaries of what I could learn in my field,” Guerrier said. 

UC Davis and Cooper’s lab checked those boxes. 

The chemical history of magma chambers 

Nearly 10 years ago, Cooper and Oregon State University geochemist Adam Kent, shifted how we view the magma chambers of volcanoes. In a letter published in Nature, they revealed that the magma chamber of a volcano can be predominantly solid for roughly 90% of its storage duration. 

“The scientific community has shifted to this idea that magma chambers are mostly crystalline,” Guerrier said. “All of the crystals and interstitial liquid magma are in a semi-mobile form, kind of like Silly Putty. And they’re stored like this until large amounts of magma are collected relatively quickly and erupt..”

This has led researchers to wonder, at what point in a volcano’s history does more magma rapidly accumulate and lead to an eruption? 

To untangle this question, Guerrier analyzes crystals found in volcanic rocks, namely zircon and sanidine crystals. Gleaning information from the crystals is accomplished via column chemistry and a method called sensitive high-resolution ion microprobe. 

“Zircon is important because it’s very resistant to weathering, so it can hold onto the information about its history and its age,” Guerrier said. “Its interior composition doesn’t change readily when it’s in different parts of the magma chamber whereas other crystals might diffuse or become altered in ways that are not helpful for dating or using for chemical composition.”

Like zircon crystals, sanidine crystals can be dated, but its crystalline form also captures information about its chemical composition when it was magma. According to Guerrier, isotopic signatures from that magma are imparted on the crystals, serving as a sort of fingerprint that can be used for further identification. 

“If you have multiple volcanic rocks from different eruptions within a similar time period, you can ask, do these crystals have similar chemical compositions?” Guerrier said.  

Isotopic analyses of these crystals give scientists an idea of where volcanic rocks originate within the magma chamber. Collectively, this information can then be used to help create a snapshot of a magma chamber’s architecture prior to an eruption.

By working with Cooper, Guerrier has the opportunity to help reveal the mysteries held within volcanoes. 

“She’s great; the school is great; it was a no-brainer,” Guerrier said of her decision to pursue her doctoral studies at UC Davis. 

 Schematic showing collapse processes of Yellowstone Caldera
Part of a schematic showing collapse processes of the Yellowstone Caldera. (Figure developed by Morgan Nasholds, Yellowstone National Park)

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