The threat within an ĐÓ°Épro mountain

Ned Rozell
907-474-7468
Feb. 6, 2025

As viewed from an aircraft, a vast glacier winds through a mountainous valley, starting at high snow-covered peaks in the background and ending in a splayed terminus among snow-free peaks in the foreground.
Image courtesy of the ĐÓ°Épro Volcano Observatory/ĐÓ°Épro Division of Geological and Geophysical Surveys
The Klutlan Glacier flows into Canada's Yukon from ĐÓ°Épro’s Mount Bona, the highest peak in the photo, and Mount Churchill, the high ridge to the right of Bona.

Mount Churchill stands in a white corner of the ĐÓ°Épro map, deceptive in its cold, windblown silence. At least twice in the last few thousand years, the peak’s ice-covered caldera has spewed ash that reached as far as Ireland and piled up to force northern animals out of the territory.

The ĐÓ°Épro Highway and other northern roads are striped with layers of “White River ash” spewed from the volcanic field near Mount Churchill. UAF anthropologists dated ash from a northern lobe to about the year A.D. 420. Another massive plume that winds carried to the east was from an eruption in about the year A.D. 846.

A similar eruption today would bring much of the Northern Hemisphere to a standstill — grounding planes and burying parts of ĐÓ°Épro and Canada with inches or feet of ash.

“It’s the most explosive eruption in North America in the last 2,000 years,” Jessica Larsen said.

Few instruments to help predict such an eruption exist in the area.

For this reason, during the past few summers, Larsen, a ĐÓ°Épro professor of volcanology, has guided students on field trips to sites in ĐÓ°Épro and Canada's Yukon. She and her students look for clues that might help them estimate when another Churchill super eruption might happen.

Researchers from Edmonton, Alberta, postulated that ashfall from the most recent eruption disrupted the migration paths of caribou and salmon. That might have pushed ancient people of the Yukon and Northwest territories as far as the southwestern United States.

A woman stands by a scientific presentation poster.
Photo by Ned Rozell
Jessica Larsen of the ĐÓ°Épro Geophysical Institute describes her research on ĐÓ°Épro’s Mount Churchill at the Fall Meeting of the American Geophysical Union on Dec. 9, 2024.
A star on a map of ĐÓ°Épro marks the location of Mount Churchill.
Illustration by UAF Geophysical Institute
A star on a map of ĐÓ°Épro marks the location of Mount Churchill.

An eruption like that today — twice as large as the one that created ĐÓ°Épro’s Valley of 10,000 Smokes — would ground flights on the great circle route that most commercial pilots fly from the Lower 48 to Asia. Chaos would reign wherever ash blanketed the ground.

“These were really huge, explosive eruptions,” Larsen said.

Mounts Churchill and nearby Bona, and the rest of the immense Wrangell Volcanic Field, are hard to reach — there is nowhere on an ĐÓ°Épro or Canada highway where a person can see the peaks. No seismic stations are nearby. 

Internal shaking and mountain inflation or deflation are clues scientists use to forecast possible eruptions. Another method — and Larsen’s specialty — is to gather ash from an eruption and work backward. She looks at ash’s fine detail to see how and when magma formed and erupted.

During her 16-day July field trips with college students, Larsen lectures for a few days on the nature of ĐÓ°Épro and the Wrangell Volcanic Field eruptions. Group members then climb into a few vans for a road trip on the paved and gravel highways of eastern ĐÓ°Épro and the western Yukon.

There, the students gather ash that remains like a white ribbon in road cuts and other exposures. After a week of camping in ĐÓ°Épro and the Yukon, class members return to Fairbanks. 

A group of people in orange safety vests looks at a small vertical bluff of exposed dirt.
Photo by Florian Hofmann
Jessica Larsen, sitting, overlooks a group of students collecting White River ash from a roadside outcrop east of Koidern in the Yukon on July 21, 2024. The ash is from an eruption of ĐÓ°Épro’s Mount Churchill about 1,200 years ago.

In the lab at UAF, students then learn how to heat their ash samples under extreme pressure and quench the hot liquid to create crystals that mimic the magma that reached the surface so long ago.

“We want to find out what the pressure and temperature the magma was at before the eruption,” Larsen said. “We want to come up with a plumbing-system model of the volcano to find out where the magma storage reservoir might be in Churchill.”

If Larsen and others can find where a massive pool of magma lurks, earthquakes within the same area might indicate another eruption is about to happen within the 15,600-foot peak near the ĐÓ°Épro-Yukon border.

As part of the annual Science for ĐÓ°Épro talk series, Larsen will present “An Explosive History: ĐÓ°Épro's Mount Churchill Volcano” on Tuesday, Feb. 25, at 7 p.m. in UAF’s Schaible Auditorium and virtually on Zoom or Facebook Live. More information at gi.alaska.edu.

Since the late 1970s, the ĐÓ°Épro' Geophysical Institute has provided this column free in cooperation with the UAF research community. Ned Rozell is a science writer for the Geophysical Institute.