High-speed lasers measure glacial movement at Big Sky Resort

BILLINGS – Many skiers and snowboarders probably don’t know it, but the 9,800-foot-high base of Big Sky Resort’s Lone Peak Tram sits atop a slow-moving rock glacier.

The Lone Peak rock glacier, as it is known, measures a mile long and possibly 100 to 200 feet thick at its maximum.

“It’s an interesting geological feature,” Stephen Crouch said. “There’s several layers of gravel on the surface and underneath that there are several layers of ice.”

Crouch is chief technology officer for Blackmore, a Bozeman-based photonics company. One of the company’s specialties is lidar – using pulses of laser light to calculate and record distances with sensors. This summer Blackmore technicians worked with Montana State University to use its portable lidar to measure the surface of the 200-foot-deep glacier in Big Couloir to see how it’s moving.

“The basic data product of a lidar system is a list of 3D coordinates,” Crouch said. “Those points correspond to locations on the surface of an object. Once you get enough you are able to define that surface quite well.”

“Blackmore has some really cutting-edge technology,” said MSU assistant research professor Colin Shaw, of the department of earth sciences. “They use Doppler-type processing to get more information from the data.”

Shaw is interested in the glacier measurements for several reasons. For one, rock glaciers are more resistant to melting. Their thick rock covering – at Lone Mountain the talus is up to 9 feet deep – insulates them from heat.

“They may soon be one of the last surviving remnants of glaciers that covered Western Montana from the last ice age,” Shaw said.

Shaw also wants to know if Big Sky’s glacier is losing mass, and if so, how fast. Is the changing climate with shorter winters and longer summers having an effect?

“Another aspect we’re interested in is the mechanics of how ice flows,” he said. “Clean ice is relatively simple: The ice deforms and flows downhill. For dirty ice, it’s a much more complicated process.”

Dirty ice can be concentrated in narrow bands, more like a geological fault, Shaw said. Impurities in the ice concentrate the strain.

“Actually, there are a lot of rock glaciers – about 300 around southwest Montana,” Shaw said. “On Lone Peak alone, there are at least a half dozen.”

Shaw said the Big Sky glacier has been measured previously by lidar in 2005, an aerial scan done for a student’s doctoral dissertation. With the new land-based survey conducted by Blackmore, Shaw and his students will be able to compare how the glacier has changed over 13 years as well as store the information for any future comparisons.

“When you are looking at images, you can rotate the model on a computer for a full 3D experience,” Crouch said.

Blackmore’s interest in helping MSU with a glacial question is to explore new applications for its lidar technology.

“This long-range technology was developed for the Department of Defense,” Crouch said.

Lidar has force protection applications at forward-operating bases where towers with sensors can monitor an area and provide troops with “better situational awareness,” he said.

Beyond that, lidar might also benefit mining companies by preventing injuries and tracking productivity, Crouch said.

“In the case of ski areas it’s a tool to monitor the surface condition of the snow,” he added.

Lidar also has forestry applications that could be used to monitor plots. But perhaps most exciting for futurists, Blackmore is working to make its lidar adaptable to autonomous vehicles. Lidar can provide detailed spatial resolution at a high update rate, Crouch explained, and Blackmore’s system has a long range, allowing the vehicle to operate at a higher rate of speed. The lidar is also sensitive to velocity, capable of measuring objects that are moving toward and alongside the vehicle.

“As geologists, we’re dealing with things that move much slower,” Shaw said, “but lidar technology does have applications even for us.”

Big Sky Resort’s engineers knew when the 2,800-foot-long tram was built in 1995 that the bottom station would sit atop a rock glacier. That’s one reason a tram, and not a lift, was constructed. Lifts require towers that would have moved as the glacier shifted.

Mike Unruh, vice president of mountain operations at Big Sky Resort, said the decision about where to locate the lower terminal was based on knowledge about the rock glacier.

“Surveys that were done before tram installation suggested it would be better suited in its current location,” Unruh wrote in an email. “The configuration of the Lone Peak Tram is such to allow for the bottom terminal to move. By installing a tram instead of a gondola and eliminating the need for towers, complications due to this movement were greatly reduced.”

Unruh said since the tram was built, it has moved several feet.

“The tram is surveyed routinely to track its movement, and inspected methodically by Doppelmayr engineers from Europe who are familiar with installations on glaciers,” he said.

The tram is one long span of cable that climbs 1,450 feet. The top tram station rests on the peak of 11,166-foot Lone Mountain. Skiers or snowboarders riding from there to the bottom of Big Sky Resort via Liberty Bowl cover 6 miles of terrain.

“From our preliminary results, it looks like the glacier is not losing mass very rapidly,” Shaw said. “But it is locally advancing on a couple of lobes.”

Shaw hopes to use the information his students have gathered to provide an information packet to Big Sky Resort’s Basecamp workers, the folks who give tours of the mountain. Those guides already provide historical and geological information where the MSU science on the glacier could be incorporated, he said.

As a skier, Shaw said his knowledge about Big Sky’s rock glacier – which in the winter has its rocky topping buried under several feet of snow – adds to his experience of carving turns down the intermediate slope.

“I’m keenly aware of the interaction between science and what’s going on on the surface,” he said.