February 24 2015— Slow landslides in permafrost slide downhill on mountain slopes in the Brooks Range of Alaska. These massive frozen debris lobes are geohazards. They pose a potential threat to the Dalton Highway, Alaska’s lone road to the North Slope.
There are 23 identified frozen debris lobes situated less than one mile uphill from the Dalton Highway. In recent years the motion of some of these frozen masses has increased. In new FrontierScientists videos “Dynamic Slope – Frozen Debris Lobes“, and “Cover The Haul Road – Frozen Debris Lobes“, join scientists pushing to measure and assess these frozen debris lobes (FDLs) with the end goal of understanding why and how they move and using that knowledge to help Alaska and the Alaska Department of Transportation & Public Facilities mitigate the risks of the FDLs.
Featured are three scientists: geological engineer Margaret M. Darrow, associate professor at the University of Alaska Fairbanks Mining and Geological Engineering Department, along with geohydrologist Ronald P. Daanen and geomorphologist Trent D. Hubbard, each with the Alaska Department of Natural Resources Division of Geological & Geophysical Surveys (Engineering Geology section).
From the Dalton Highway a careful eye can spot drunken trees growing tenaciously along with other vegetation atop FDLs. Drunken trees have been partially toppled by lobe motion and then self-adjusted their growing pattern to vertical, leaving curves in their trunks.
FDLs can also be noted in aerial photography and even satellite imagery. Check out the project’s official website at http://fdlalaska.org/, where you can see how near to the highway the nearest lobe looms. The same lobe can be found at this link, or navigated to by entering coordinates (67.811376, -149.818801) and choosing ‘Earth View’. The satellite image on Google Maps isn’t up to date, but you can see the elongated mass of the lobe and the advancing toe (front) of the lobe.
FDLs were long presumed to be inactive. They didn’t even garner a unique name until 2012. Yet their rate of motion has increased during the last decades. You can observe the motion.
The fastest motion was observed in a lobe labeled D. The scientists took note of cracks running across the high reaches of FDL-D, cracks in the catchment likely to be infiltrated by water. Then FDL-D sped up, averaging speeds around 150 feet per year over three years.
FrontierScientists joined the scientists atop the most massive lobe, FDL-A. It’s the closest one to the Dalton Highway, it moves an estimated 22,000 tons of debris per year down slope, and on August 21, 2014 it was merely 136.6 feet away from the highway. On FDL-A the scientists pointed out cracks in the catchment reminiscent of the ones they’d seen on the smaller FDL-D. If the motion of FDL-A follows similar rules to those FDL-D follows, FDL-A could feasibly pick up speed and reach the Dalton Highway in less than a year. If not, it’s projected to reach the highway in less than a decade. And there’s nothing in place to stop it from eating the road.
The current plan is to realign the highway near FDL-A’s location at milepost 219. The Alaska Department of Transportation and Public Facilities will change the road to sit 400 feet further from FDL-A’s toe. It’s a move that will buy time.
Darrow, Daanen, and Hubbard told FrontierScientists of plans to build a model, a data-derived computer simulation capable of forecasting how useful different mitigation strategies would prove; what might effectively divert or slow a massive debris lobe? The information they were gathering was designed to learn just that. But without additional funding for subsurface exploration (involving tasks like drilling and installing instruments underground) the scientists are unable to get enough data to properly constrain a model. They pursue more information to make an accurate and effective simulation.
What will happen with Alaska’s frozen debris lobes, the Dalton Highway, and Alaskan transportation infrastructure? Time will tell. For now, you can take a video-hike up FDL-A with the scientists who care so much about this massive and modern-day issue.
View Alaska videos at www.FrontierScientists.com, where scientific discoveries in some of the Arctic’s most remote and dramatic landscapes are chronicled in short videos, Twitter feeds, blogs and web reports. Frontier Scientists shares first-person accounts and real-time insights from leading scientists including archaeologists, grizzly bear biologists, volcano researchers, climate change specialists, and more.
“We want to let travelers, teachers, students, aspiring scientists, and anyone else interested in science feel as if they are with scientists as they track grizzlies or take the temperature of permafrost in a borehole,” explains Liz O’Connell, video director for Frontier Scientists.
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Frozen Debris Lobes project
- ‘Rapid movement of frozen debris-lobes: implications for permafrost degradation and slope instability in the south-central Brooks Range, Alaska’ R.P. Daanen, G. Grosse, M.M. Darrow, T.D. Hamilton, and B.M. Jones, Natural Hazards and Earth System Sciences, 12, 1521-1537, 2012 doi:10.5194/nhess-12-1521-2012