Carol Finn (MGeol’82; PhDGeoPhys’88) and her team of researchers are the first to use electromagnetic sensors to map the hydrothermal network — the plumbing — under Yellowstone National Park (YNP). Finn, lead author of the , is a research geophysicist at the U.S. Geological Survey in Denver who specializes in geothermal mapping and natural hazard assessment.

What was best about your time at ŷ���ڱ���Ƶ? 

My fellow graduate students. There was tremendous camaraderie, and I am still friends with many of them. My advisors also gave me a lot of freedom to pursue my research in geophysics. Plus, what’s not to love about campus? 

What inspired your interest in geophysics and natural hazards?

Geophysicists use remote means to look inside the earth, similar to doctors who use X-rays, MRIs and CTs to scan the body. I love being able to reveal hidden knowledge. My first projects were using geophysical data to look for hot rock under volcanoes in the Cascade Range. This is where my interest in volcanoes started. My later work in the Cascades and Alaska in-volved looking for buried hydrothermally weakened rock on the volcanoes that might source very large landslides. Being able to contribute to the understanding of these hazards is very gratifying because the knowledge helps local communities develop mitigation strategies to save lives in case of a landslide. 

What is especially interesting or important about Yellowstone?

Everything! Most people who visit Yellowstone are awed by the beauty and seeming magic of the geysers, hot pots and other thermal features. Yellowstone contains the largest number of thermal features in the world and provides an analog for geysers on other planets.

What is your data collection process? 

A helicopter flies with an 80-foot-diameter loop of wire dangling above the ground. The loop sends downward repeated electromagnetic signals that create currents in electrically conductive bodies in the subsurface. The signal of these currents is sensed by the wire loop. The technique is effective in environments like Yellowstone because cold water, hot fluids and clays resulting from hot fluids passing through them conduct electricity, whereas dry volcanic rocks do not. 

What are the potential applications of your findings?

Despite decades of studies, the plumbing system that links legendary surface features to deep thermal fluids beneath YNP was previously unknown. It’s important to understand how it works because there’s a lot of geological activity underneath Yellowstone. Understanding the connectivity of the plumbing system in YNP is also useful to determine whether geothermal energy extraction outside of the park might influence hydrothermal activity in the park. 

  Submit feedback to the editor

Photos courtesy Carol Finn 

Off

In December 2021, a trio of ŷ���ڱ���Ƶ scientists in a convoy of 4WD trucks sought to discover how life persists on Argentina and Chile’s Ojos del Salado, the world’s highest volcano and home to some of the planet’s driest areas. The team — Brian Hynek, geological sciences professor and LASP research associate, and graduate students Adam Solon (EBio’16; PhD’23) and Amanda Steckel (MAeroEngr’15; PhDGeol’24) — were the first researchers to explore and study some of the highest points on the Argentinian side of the mountain. Their work may inform future research into life beyond Earth, such as on Mars or on one of Jupiter’s moons, Europa. 

  Submit feedback to the editor

Photos by Brain Hynek, Amanda Steckel and Christian Vitry 

Related Articles

When the Earth took a turn for the worse in A.D. 536, what was to blame? Anthropology professor Payson Sheets thinks the answer lies in a plastic bag. 

In the long and tumultuous history of planet Earth, A.D. 536 was a particularly rough year.

A veil of dust hung high in the stratosphere, filtering out the sun’s warmth and wreaking havoc around the globe for a decade, with the Northern Hemisphere hit hardest. Oceans cooled, evaporation stalled, rain became scarce and crops withered or froze. In northern China, scribes wrote of famine, mass death and loss of faith in the emperor. In Europe, monks described being able to, for the first time, walk “dry footed” across all the rivers and lakes because the water had turned to ice. In Rome, plague set in. In Mexico, commoners set torches to palaces, looted tombs and butchered elites.

“The world became unlivable,” explains anthropology professor Payson Sheets (Anth’67, MA’69), citing written texts, archaeological evidence and tree-ring data all pointing to what has become known as “the mystery of A.D. 536.” “There is no doubt that it happened. The question is what caused it? Was it a volcano? A comet? Historians have been debating it for decades.”

Now, thanks in part to a plastic bag of volcanic ash Sheets brought home from a graduate school field trip to El Salvador in 1969, he and an interdisciplinary team of researchers from across the country believe they are closing in on an answer. They suspect a massive eruption of the Ilopango volcano in El Salvador is likely to blame for the cataclysmic events of A.D. 536. Now they’re digging deep to find out for sure and see what lessons Ilopango can teach us today.

“A massive eruption happens about every 1,000 or 2,000 years, so another one will likely happen in the next few centuries and it will affect economies and culture and climate,” says paleoecologist Robert Dull, a senior research fellow at the Environmental Science Institute at the University of Texas, who is collaborating with Sheets. “To understand how these other events played out is critical for helping anticipate such events in the future.”

Born in Boulder in 1944, Sheets earned bachelor’s and master’s degrees in anthropology at ŷ���ڱ���Ƶ-Boulder before heading to the University of Pennsylvania for a doctorate in the early 1970s.

He was excavating an ancient pyramid at a site called Chalchuapa in far western El Salvador in 1969 when he stumbled upon a fine chalky powder. Coming from ŷ���ڱ���Ƶ where volcanos are rare, he didn’t immediately recognize it as ash. But once he did, questions flooded his mind: Where did it come from? How old was it? How big was the event that caused it? And what was the human toll? 

He scooped several cups of ash into a plastic bag, marked it with the location — Structure C-36 — and tucked it in his backpack for the flight home.

In Miami the customs agent also was intrigued with the white powder.
 

• Researchers are exploring whether Ilopango volcano, near El Salvador’s capital city of San Salvador, played a role in the  cataclysmic events that took place in the 6th century A.D.
• In Mexico, commoners set torches to palaces, looted tombs and butchered elites.
• Rome was hit by plagues.
• Water turned to ice in Europe, and monks described being able to walk “dry footed” across all the rivers and lakes.
• In northern China residents 
  experienced famine, mass death and loss of faith in the emperor.

“He took out a big knife and tasted it,” recalls Sheets, clutching the bag of ash that he still keeps in a locked drawer in his office. “He thought he had a big drug bust on his hands.”

The discovery would ignite a lifelong fascination with volcanoes and their impact on ancient cultures, which has guided him from Panama to Costa Rica to Nicaragua, often during times of political strife that make his work a risky endeavor.

In 1971 Sheets used radiocarbon dating of the ash to publish the first estimated date of the Ilopango eruption to somewhere between A.D. 32 and A.D. 448. In subsequent years, he continued to uncover similar samples across western El Salvador, shrouding a wealth of archaeological treasures that hinted at the scope and impact of the disaster. 

“It killed every living person, animal, bird, fish and insect in a huge area overnight,” he says, noting that the eruption killed roughly 100,000 people in El Salvador alone and turned the lush jungle to a vacant desert. “The more I have researched that ash, the more I have learned how huge it was.”

But the link to A.D. 536 wouldn’t come until decades later. 

The Ilopango sample migrated to the back burner, replaced by other projects. In the late 1970s Sheets served as lead archaeologist on Ceren, a 1,400-year-old Mayan village, which is now a World Heritage Site known as “the Pompeii of the Americas.”
And for much of the 1980s, a ruthless civil war made travel to El Salvador difficult.

“People were slaughtering each other,” Sheets recalls. “I would still go for short visits, but I couldn’t take students or family there for about eight years.”

Fast forward to the 1990s and Dull — then a graduate student working in El Salvador — stumbled upon some of Sheets’ early writings about Ilopango and became intrigued. He reached out to Sheets with an invitation to collaborate.

“Payson is the grandfather of volcanoes and archaeology in this part of the world,” Dull says. “I learned about the event for the very first time from an article he wrote.”

Using samples from trees buried and preserved by the volcanic ash and state-of-the-art radiocarbon dating by John Southon of the University of California, the team worked together to refine the estimated date of Ilopango’s eruption to somewhere around A.D. 536, give or take a few decades.

Then, in 2008, a team of ice core researchers from Copenhagen published a pivotal study reporting that ice cores taken from Greenland and Antarctica showed a significant spike in sulfur around A.D. 536, a phenomenon that likely resulted from “a large, explosive, near equatorial volcanic eruption.”

Sheets and his colleagues began to connect the dots. Was their volcano the culprit?

“There is plenty of circumstantial evidence but there is no smoking gun yet,” says Sheets, who is still reluctant to say definitively whether Ilopango caused the events of A.D. 536. “But we are going after it.”

As his colleagues in the natural sciences toil to come up with a more precise date of the Ilopango eruption and determine whether it is linked to the cataclysmic events of A.D. 536, Sheets hopes to learn more about the eruption’s cultural impacts.

“What societies were resilient and what societies were not?” he asks.

For now, what they can say for sure is this: Ilopango was likely the biggest volcanic eruption in Central America in the last 84,000 years, and among the most powerful in the history of the planet.

And the events of A.D. 536 — whatever their cause — forever changed life on Earth.

“It is mind-boggling to think about the potential impacts it had on cultures all around the globe,” Dull says. “It was a real pivot point in human history.”

Photo © Richard Roscoe/Stocktrek Images/Corbis/Illustration ©iStock.com/diane555

Off