Student Sharon Bubsy examines one of the seismometer stations in remote areas of the Yukon and Northwest Territories. PHOTO: courtesy of the Yukon College

 

Researchers investigate how Earth movement on the coast can affect inland mountains

The white-capped Mackenzie Mountains, which spill over the border between Yukon and the Northwest Territories, are surprisingly active… for a pile of rock.

Each year, the mountains are growing a few millimetres taller. It may not sound like much, but it’s significant in geological terms, where it takes thousands of years to form rock, and the fastest uplift rates — the speed of elevation change on the Earth’s surface — are about three kilometres over one million years.

A team of scientists from the University of Alaska, Fairbanks, Colorado State University, and Yukon College has been exploring the cause of this movement through an international project funded through the United States National Science Foundation.

Here’s what the researchers know: There’s a lot of underground tectonic action happening in and around Kluane National Park. Just to the southwest, the Pacific Plate meets the North American Plate in the Gulf of Alaska. When those two plates move and collide, they cause a space problem. And that triggers considerable seismic activity, which can result in earthquakes, like the one in Haines Pass in 2017.

“It’s a high-stress environment,” said Dr. Joel Cubley, one of the project’s researchers and an instructor at Yukon College’s Geological Technology Program. “A fragment of the Earth’s crust is wedged against the North American Plate, causing rapid uplift of the Coast Mountains in Kluane and southeastern Alaska.”

It’s not surprising that this tectonic stress is causing coastal mountains to move, but astonishingly it also seems to be moving the Mackenzie Mountains, which are located more than 800 kilometres inland.

Cubley and the team are trying to figure out what’s going on: How can that stress transfer so far? And what geologic structures allow for this movement of Earth’s upper crust? To find these answers, they’re using earthquake data to help image the Earth’s subsurface beneath parts of Alaska, the Yukon and the NWT.

Between 2015 and 2017, the research team installed 37 seismographs and three GPS instruments along a rough line starting in Skagway, Alaska, crossing the Yukon and the Mackenzie Mountain range, and then extending to the edge of Great Bear Lake. These instruments record earthquake data and help geoscientists build a picture of geologic structure and activity far below the Earth’s surface.

“It is such an intriguing project,” said Sharon Busby, a Yukon College geological technology student who assisted the professional scientists with placing and monitoring the equipment. “It was a great learning experience for me to help with research that could potentially provide new insight into the inner workings of the Earth.”

Busby came from Manitoba to study at the College after reading about the work and research opportunities available to students there.

“I also love being outdoors,” she added. “Backpacking, mountain biking and hiking – anything that will get me to go out and explore the mountains.”

In July 2016, when Busby and the research team loaded their gear into trucks to begin 10 days of field work, she knew she had found the adventure she’d sought.

“I came to the College with an interest in geology, and it was so encouraging for me to be able to work alongside professional scientists,” she said. “It gave me the confidence that I could carry on with this type of work.”

In fall 2016, they went back out into the field to check on the instruments and found that a few had been damaged: One had paw prints on it, likely from a bear encounter, and another had a bullet hole through it, possibly a stray from a hunter’s rifle. They repaired the damaged sites and replaced the instruments’ batteries, so they would continue providing accurate readings.

In 2017, Busby graduated with a Geological Technology Diploma. With her combination of education and experience, she was able to springboard into a position with Golder Associates where she puts the skills learned at Yukon College to use as a Geo-Environmental Technician.

Meanwhile, the Mackenzie Mountain project continues. In summer 2018, Cubley and co-researchers will retrieve the sensors and begin to compile results to gain a greater understanding of the mountains’ movements and more broadly, the inner workings of the Earth.