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Only in Alaska? Creeping frozen landslide threatens critical highway and pipeline

  • Author: Laurel Andrews
  • Updated: September 27, 2016
  • Published August 13, 2013

A massive landslide of frozen debris and ice is inching its way toward the Dalton Highway, outside of the Gates of the Arctic National Park Preserve, and nobody is quite sure how to stop it. If left to its own devices, in the next ten years the little-understood formation will reach the highway which serves as the only ground link between Alaska's road system and its critical North Slope oil patch. If the slide isn't stopped, it will eventually threaten the trans-Alaska pipeline itself.

As new evidence shows that the formations -- called frozen debris lobes -- have sped up over time, researchers are calling for more studies on the huge, frozen landslides, and the Department of Transportation is assessing how to best handle the threat to the state's infrastructure.

The best solution, for now, may be to simply get out of the landslide's path.

Frozen landslides threaten Alaska’s economy

There are around 200 frozen debris lobes mapped out in the Gates of the Arctic National Park and Preserve, which is the northernmost national park in the U.S. and is located entirely above the Arctic Circle. The slowly-moving landslides are frozen masses of weathered bedrock eroded into collections of sediment, ice, water, and unfortunate bits of foliage consumed in its wake.

"These features seem to be eating trees," said Ronald Daanen, a geohydrologist with the Alaska Division of Geological and Geophysical Surveys, noting that he had found a piece of wood in one lobe that was 1,300 years old.

The lobe in question, named "FDL-A" is huge, at about three-quarters of a mile long, more than 600 feet wide and 80 feet tall. It is now 150 feet from the Dalton Highway. Moving at its current rate, the landslide will reach the road in around 10 years.

The Dalton Highway is a 414-mile road that runs from the Interior community of Livengood, about 80 miles north of Fairbanks, to Prudhoe Bay on the Arctic Ocean coast. The highway runs parallel to the trans-Alaska pipeline, and is traversed mainly by the trucking industry, bringing supplies up and down from Prudhoe Bay. The highway remains open year-round, and has only been shut down due to planned maintenance or by avalanches at Atigun Pass, north of Gates of the Arctic National Park.

Alyeska Pipeline Services Co. spokesperson Michelle Egan said that the consortium in charge of the line is well aware of the formations, and is working with the state to stay "well ahead of any permafrost changes" that could threaten the pipeline's infrastructure.

Should the highway shut down, "it would not be a trivial thing," said Jeff Curry, Alaska Department of Transportation's northern region materials engineer. He said it would be a "very big blow to Alaska's economy," which is heavily dependent on the North Slope's oil and gas industry.

How do debris lobes move?

These frozen landslides were formed sometime after the ice age, between 5,000 and 10,000 years ago. The lobes, said Daanen, are made mostly of permafrost, but they carry liquid water inside the frozen earth, an "uncommon phenomenon." Pressure within the mass keeps the water from freezing, and gravity helps push the mass along its path.

The debris lobes also have some similarities to glaciers. The "rate of movement is very similar," Daanen said, varying seasonally and between individual lobes, with each lobe moving at a different pace. The lobes also have cracks on the surface which mimic cracks in glacial ice.

No one is quite sure how the formations came to be. "One of the mysteries is really what's driving these things to form," Daanen said.

One theory is that during the ice age, the tops of hills that remained elevated above the glaciated landscape were subject to harsh erosion, and the sediment wore away and accumulated on the sides of the hills. Once the glaciers disappeared, these frozen blobs of debris "just started moving down the hill," Daanen said.

Whatever the cause, these massive lobes seem to be speeding up in the 21st century.

From 1955 to the early 2000s, FDL-A moved at about a half-inch a day. But around 2004 or 2005, the lobe's speed increased. "I think something has shifted since that time," Daanen said. Now, the lobe is moving around an inch a day.

Scientists also have their eye on one of the lobes that is moving much faster, named "FDL-D", which galloped 150 feet last year -- a monumental pace for a frozen landslide.

It's possible that FDL-A could also increase in speed, as it seems to be showing similar characteristics as FDL-D, specifically increased cracking along the top of the formation.

Discovered and rediscovered

USGS Geologist Thomas Hamilton first mapped out the frozen debris lobes in the early 1970s, as part of the pipeline planning process.

Decades later, in 2007, Daanen was traveling on the Dalton Highway, measuring snow depths on the North Slope, when he spotted the formations.

"I thought I should just keep an eye out for drunken forests, because that's one of the signs of global warming," Daanen said. A drunken forest -- where the trees are criss-crossed and falling over -- occurs when permafrost thaws and the ground re-settles, causing the trees to shift.

Daanen began to see drunken forests just north of Coldfoot, about 250 miles north of Fairbanks. Then he noticed that the reeling trees were all on slope-like features. His curiosity piqued, Daanen snapped some photos of the slopes and went along his way.

Daanen met up with Hamilton later that year and told him about his find. "He got very big eyes," Daanen said. Hamilton was happy that his work from years before had been brought back to the table. He was also "kind of surprised that a permafrost scientist picked up on it and not a geologist," Daanen laughed.

"That's kind of how the research got started," Daanen said.

A research grant with the University of Alaska Fairbanks followed in 2008, and studies on the frozen landslides began. Daanen and his colleague Margaret Darrow have been studying them ever since.

Hamilton originally called the lobes "flow slides," but Daanen, Darrow and Hamilton renamed the formations to "frozen debris lobes," a generic name that describes the formation aptly enough.

The Department of Transportation was first clued in to the dangers of the approaching lobe after Daanen told them about the issue.

"Initially we were not excited about it," Currey said. "We have to be a little skeptical when somebody says there's an emergency."

Yet as additional data was brought to the table, indicating that the lobes were moving faster than before, the department "recognized that it was a real issue."

If you can’t stop it, move the highway

The big question surrounding the frozen debris lobe: How can we stop it from slowly devouring the state's infrastructure?

While Daanen has found no "magic bullet" so far, he is eyeing the water inside the lobes as a possible key to stopping their movement. If that water could be turned to ice, the landslide could potentially be halted in its tracks, he said.

Moving the road seems to be the solution so far. While DOT is still in the environment assessment stage of planning, relocating the road "looks to be the most favorable right now," design project manager Jeff Organek said.

The realignment of the road is wrapped into part of a larger, 26-mile revamp of that section of the highway that involves widening and paving the highway.

DOT will likely shift the road 400 feet to the left, as far as possible before the highway runs into the pipeline it runs parallel to. "That will buy us quite a bit of time to learn more about the frozen debris lobe," Currey said.

To weave the road around the creeping frozen menace will take several years and several million dollars, at least. At this time "we don't really know how long the realignment is going to be," Organek said. A conservative estimate hovers around 2 miles of road, or about $4 million.

DOT will have the environmental assessment concluded in the spring of 2014. With the lengthy contract and permitting processes ahead, construction on the new route will probably commence in the summer of 2016.

Will prowling lobe devour old road?

The old road will stay in place, and DOT will be watching to see how the lobe affects it. The lobe may just plow right over the road, consuming it as it has with unlucky trees. Or, the road embankment may ease the lobe's movement, Currey said.

"'I think it's going to push the whole road away," Daanen said.

Daanen will be returning to the site of FDL-A at the end of August. There's still lots of work to be done, he said, and little funding to assist researchers.

"We really need to get more data."

Although Daanen recently left the University of Alaska Fairbanks to work for the state's Geological and Geophysical Survey department, he will continue to research the lobes in his spare time. "It would be silly not to continue," he said.

Contact Laurel Andrews at laurel(at)

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