Unleashed by Warming, Underground Debris Fields Threaten to ‘Crush’ Alaska’s Dalton Highway and the Alaska Pipeline

When the highway and pipeline were planned in the 1970s, the debris “lobes” were frozen solid. Now, they’re monsters devouring everything in their paths.

The Trans-Alaska Pipeline crosses the Yukon River July 21, 2002 near Dalton Highway in Fairbanks, Alaska. Credit: Barry Williams/Getty Images
The Trans-Alaska Pipeline crosses the Yukon River July 21, 2002 near Dalton Highway in Fairbanks, Alaska. Credit: Barry Williams/Getty Images

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When Alaska state engineer Jeff Currey heard about frozen debris lobes inching toward the Dalton Highway, the first thing that flashed in his mind’s eye was the campy 1958 horror movie “The Blob.”

This thing called a debris lobe sounded farfetched to Currey, who has worked 21 years for the Alaska Department of Transportation and Public Facilities.

It didn’t seem plausible to him that a massive, underground mix of rocks, soil and trees was relentlessly inching toward the highway 200 miles north of Fairbanks near Coldfoot. The 414-mile thoroughfare begins in central Alaska north of Fairbanks and continues north to Prudhoe Bay on the Beaufort Sea. 

“Frankly, we poo-pooed it,” Currey said about the time a decade ago when transportation officials were first alerted to the lumbering mass.


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He summed up the consensus among highway officials back then: “OK. It’s there and moving slow; nothing for us to be concerned about.”

But the more Currey and other engineers considered the unrelenting characteristics of one particular blob—identified as Frozen Debris Lobe A—they soon understood the dire consequences facing the Dalton and the Trans-Alaska Pipeline, which the highway was built to service in 1974 and parallels the road. The lobes crush and envelop everything in their path.

Most disquieting to Currey was the mounting data that showed that Debris Lobe A and more than a dozen others were picking up speed, unharnessed and accelerated by warming temperatures triggered by climate change. Speed in the case of debris lobes may be relative when talking about a couple of feet of movement a month and the road and pipeline are still a mile away, in some cases, but there’s nothing that can stop the lobes. 

The snickering hushed for good when it became clear around 2015 that Debris Lobe A was ultimately going to obliterate a section of the Dalton; and continue on toward the pipeline. 

“Now it’s serious,” Currey said.

The threat has Currey and the transportation department keeping a watchful eye on the lobes, though he says he doesn’t “dwell” on them. The transportation department, which has contributed more than $200,000 to scientists studying the lobes, have been joined by academics, the oil and gas industry and other state and federal agencies to assess the threat and work on solutions to defend the road and pipeline. 


Alyeska Pipeline Service Company, a syndicate of oil companies that owns and operates the Trans-Alaska Pipeline System (TAPS), is among the agencies financing investigations and has pledged an initial $100,000 to fund studies aimed at better understanding the dynamics of the lobes and the threat they pose to the pipeline. 

 Michelle Egan, a spokeswoman for Alyeska, said the company is working with other agencies and organizations to monitor natural hazards and changing environmental conditions in Alaska.

 “Alyeska’s integrity management program includes a team of engineers that specialize in monitoring and protecting the system from external forces, including frozen debris lobes,” she said. “Mitigations that protect the integrity of TAPS are under consideration and will be worked with these partners as well as regulatory agencies.”

Egan declined to elaborate on those mitigation measures.  

Climate Change Has Unleashed the Lobes

Alaska, one of the fastest warming regions on Earth, is heating up faster than any other U.S. state, according to the Fourth National Climate Assessment, which was released in 2018. By the middle of the century, the state’s highest daily maximum temperature could increase between 4 and 8 degrees Fahrenheit.

The warming has put the pipeline, which carries 20 million gallons of crude oil a day,  and the Dalton, which acts both as a lifeline for remote Arctic villages and the supply link to the oil fields, in jeopardy.

Alyeska is in the midst of projects to install ground chillers below an elevated segment of the pipeline 57 miles northwest of Fairbanks to halt the thaw of permafrost that has deformed several of the braces holding up the pipeline, and is working along a northern stretch of the pipeline to fortify it against increasing flooding from the Sagavanirktok River. 

At the same time, the state transportation department has spent millions over the past five years to raise six sections of the Dalton so that the roadway is above flood levels where it hugs the pipeline’s route.

Now climate change has unleashed the debris lobes and hastened the movement of these earthen behemoths.  

State transportation officials and scientists have identified 43 frozen debris lobes along the Dalton Highway and TAPS corridor in the southern Brooks Range. Twenty-three of them are uphill and in some cases a mile or less from the road and pipeline, and sliding faster every year. Yet, unlike building barriers to deflect flood waters or installing ground chillers to halt permafrost thaw, there are no mitigation measures so far that can stop the lobes.

Researchers, including the U.S Geological Survey and University of Alaska, first described the effect of global warming on the lobes in a 2012 study that concluded “frozen debris-lobes have responded to climate change by becoming increasingly active during the last decades, resulting in rapid downslope movement.”

Margaret Darrow, a professor of geological engineering at the University of Alaska Fairbanks, is one of the principal lobe researchers who has measured the movement of the lobes since 2012, noting in one early study the lobes demonstrate “characteristics of increasing instability.” In the succeeding years, she said in an interview, that hasn’t changed as the pace of the lobes continue to quicken.

“Given the trend that we have right now, we don’t know what it means for the future,” she said.

Ron Dannen, a geohydrologist with the Alaska Department of Natural Resources, who, along with Darrow, was one of the authors of the reports, has been studying the lobes for more than a decade, hiking over the lumps, digging into the masses and deploying an array of devices to monitor them. 

What he sees happening is alarming.  

“These things are an unstoppable force,” he said. “They are coming awful close to the road and pipe; and we simply do not know how to stop them. Right now they will destroy the road and pipe.” 

In the face of that awesome power, “to do nothing would jeopardize the highway and pipe,” said Daanen, who calls the lobes an “incredible combination of physics and geology.”

Still Years Away

While the destruction of the road and pipeline appears inevitable, it’s not imminent. Daanen and other scientists and state officials have tempered panic with confidence that the lobes are still years away from reaching the highway and the pipeline. 

“That doesn’t mean there is a sense of relief,” Daanen said. “It means now is the time we have to make finding answers a priority.”

Some of those answers could come next year because Frozen Debris Lobe A—the poster child of debris lobes—is about to thump into an abandoned section of the highway. 

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Lobe A is about three-quarters of a mile long, more than 600 feet wide and 65 feet deep. There’s no calculating the energy it carries, but it topples trees, shucks aside boulders, devours the landscape and mangles scientific instruments left in its path. Researchers estimate it could slam the roadway with 22,000 tons of debris.

“When we explained this problem, we told them that this thing is faster than you think and it’s bigger than you think,” Daanen said about a meeting with transportation officials in 2013. 

The lobe, which is one of eight lobes being closely monitored, is believed to have started sliding out of its catchment basin about 15 years ago. Measurements taken between 2013 and 2014 using everything from sophisticated GPS devices to stakes pounded into the ground showed the lobe was sliding toward the highway and pipeline at slightly less than 16 feet a year. But it’s been accelerating ever since. Between 2019 and 2020, the last full year measurements were available, the rate of movement doubled to more than 32 feet a year. (Based on incomplete data for this year, researchers say they believe movement of the lobe has “slowed some.”)

At the end of July, the lobe was 19 feet from the old section of highway. On Dec. 15, the lobe had closed to within seven and a half feet, confirming the relentless march of the lobes and validating the worry the lobes may ultimately engulf the Dalton and Trans-Alaska Pipeline. 

Scientists have documented even the daily, incremental movement of the lobe. During the early 2000s, when movement was first detected, the lobe was creeping along at about 0.04 of an inch a day. Daily tracking of Debris Lobe A by the University of Alaska Fairbanks indicates the pace has increased to one inch a day. A time-lapse collage from January to October 2021 shows the lobe marching downhill toward the abandoned highway.

Daanen uses another metric to measure the movement of Debris Lobe A. It’s not all that scientific, though it is telling. A decade ago, it took him 30 minutes to walk to the leading edge of Debris Lobe A from the Dalton Highway. Today he covers the distance in a couple of minutes. 

Obscure as these debris lobes may seem, they represent the ever widening breadth of climate change assaults on the Alaskan environment. Melting glaciers, disappearing sea ice, thawing permafrost and wildfires are the iconic and highly visual consequences of climate change in Alaska. But the lumbering masses embody the reach of extremes triggered by global warming, said Gabe Wolken, a geologist with the Alaska Department of Natural Resources.

“Debris lobe acceleration really underscores how climate change affects the various elements of the cryosphere,” he said.

Rerouting the Dalton

When state officials realized that the old section of the highway was in the bull’s eye of Lobe A, it became a race against time to develop a protection plan. The Dalton is known as the Haul Road because of its role as the conduit for trucks delivering critical supplies to North Slope communities and oil field operations. It also serves as the lifeline for the pipeline, allowing vital access for inspections, maintenance work or emergency response.

The Alaska Department of Transportation estimates about 200 vehicles a day travel the Dalton, about half of which are commercial trucks supporting oil field work and native communities with approximately 2,500 tons of goods and supplies. 

Transportation officials have spit-balled a number of solutions to protect the highway, including blowing up the lobe, building a bridge over it and digging it up and hauling it away. There was even the thought of injecting liquid nitrogen into the pile to fast freeze it in its tracks. 

Ultimately, the state decided the best strategy was to realign a 4,000-foot section of road. The new segment was completed in 2018 about 400 feet away from the debris lobe at a cost of $2 million. The pipeline sits another 260 feet away. Those distances will buy some time, though there is much uncertainty about how the acceleration rate of the lobes will be influenced by continued warming.

The old section of the highway was left in place as bait for the lobe. Researchers and engineers want to sit back and watch the collision. They have implanted seismic sensors, time-lapse cameras and markers to record the slow death of the old road. Its demise will give life to the better understanding of the destructive nature of the lobes. 

Once Debris Lobe A has conquered the abandoned section of highway, Daanen, Currey and others say they hope to divine important clues on how to handle the other gigantic earthen slugs that have crept to within a mile of the highway and the pipeline, including Debris Lobe D, which is in a relative sprint, running at 150 feet a year.

“We think we can learn a lot from this and use that information to figure out how best to protect other sections in the path of these lobes,” Currey said.

Unleashed by Thawing Permafrost

Scientists believe the lobes were formed sometime after the last ice age, between 5,000 and 10,000 years ago, when retreating glaciers carved out bowls that then collected dirt, rocks, trees and other material. Water and snowmelt mixed in and froze, helping make permafrost.

For eons, the permafrost locked the lobes in place.

They were still solidly anchored in the late 1960s and early 1970s when they were observed by a U.S. Geological Survey geologist mapping the proposed North Slope route of the pipeline. At the time, the lobes were thought to be inactive and immobile.  Certainly, they weren’t considered a threat to the pipeline that would open in 1977 and cover 800 miles from Prudhoe Bay in the north to Valdez in the south.

But temperatures in Alaska began to warm.

The heating began to take its toll on the permafrost, causing it to thaw. That set off a cascading series of events that awakened the frozen debris monsters and set them on a slow-moving collision course with the pipeline and the highway.

Daanen, then a University of Alaska Fairbanks researcher, and his colleagues first detected something strange about the lobes just after 2005. They noticed some trees were kind of cockeyed, so oddly rotated that they earned the nickname “drunken trees.” Initially they thought this was an indication of thawing permafrost. It was. But it also signaled something bigger, they discovered. 

Hiking onto the lobes, the scientists saw giant spruce trees split open and twisted. Some trees were turned upside down, with turned-up roots facing the sky. They observed huge cracks in the earth. These were sure signs the thing they were standing on was moving, Daanen remembered.

The movement likely started with the thawing permafrost, which released the grip on the lobes and allowed them to begin their initial, barely perceptible creep. As the earth moved, it cracked open. The fissures allowed water from melting snow and increasing rainfall triggered by rising temperatures to seep into the lobes. That increased the weight in the lobes that in turn added momentum to downward movement. That movement led to bigger cracks that allowed more moisture into the lobes—all the time the permafrost continued to thaw.

“With continued warming, it doesn’t look good,” Daanen said. “The conditions will add to the acceleration of the lobes.”

In the 1960s, the Lobes Were Frozen Solid 

Developers of the Trans-Alaska Pipeline were starting to develop plans in the late 1960s and early 1970s for the route the 800-mile pipeline should take. The route had to be direct, cost effective to build and out of harm’s way.

It was the job of Tom Hamilton, a newly minted U.S. Geological Survey geologist, and his colleagues to identify and map potential natural hazards that could befall the pipeline in Northern Alaska. Their work would be used as one metric to select the pipeline’s route—and identify any potential threats posed by nature that could lead to the destruction of the pipeline. The surveyors highlighted earthquake faults, soft spots in the ground from buried lake sediment and landslide chutes as potential threats. 

The debris lobes did not make the list. 

It’s not that the lobes went unnoticed. Hamilton and other geologists flew over them for a bird’s eye view, hiked to them for close up inspection and mapped their locations. There was no cause for alarm, Hamilton said.   

The debris lobes that are on the move now, marching toward the pipeline and highway, were then locked solidly in place like fence posts anchored in concrete.

“They were stable and didn’t appear to be going anywhere,” Hamilton said. “They seemed to be frozen in place. So, we figured there was no cause for alarm.”

Hamilton, 85, who has been retired from the USGS for 17 years, recalled standing at the toe of one of the debris lobes and thinking how rock solid and firmly anchored they appeared. 

“It didn’t seem like they’d be moving anytime at all,” he said.

That has changed now that temperatures in Alaska are on the rise, giving Hamilton pause to think how his assessment of the debris lobes would be different today.

“They would have been considered a hazard back then if we’d have seen what we see today,” he said. “No doubt.”