Melting Permafrost Triggering Landslides Across The Arctic; Denali NP's Only Road The Beta Test
On a route traveled by hundreds of thousands of Alaska tourists each year, danger looms. Midway along the 92-mile road that winds through Denali National Park, at a spot with an elevation of 3,500 feet and spectacular views of the Alaska Range and the braided rivers that flow out of it, an unstable wall of rock, ice, soil and clay rises precariously. The slope into which the road was cut eight decades ago is already collapsing gradually — and there are fears that it could collapse much more suddenly in the future.
The site, called Pretty Rocks, near Polychrome Overlook and along an ever-narrowing section of road perched on a steep cliff 1,000 feet above the river valley, can be nerve-wracking for travelers, most of them ferried into the park by shuttle bus. For Denny Capps, the park’s geologist, it’s a persistent source of worry. The slope had been creeping slightly for several years, but its movement began to speed up in 2014, and it increased five-fold in the last year, Capps said. In the first seven months of the year, movement averaged about 2 inches a day for the first eight months of the year, he said. In August and early September, according to park measurements, it sped to about 3.5 inches a day.
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Pretty Rocks, though considered the most dangerous, is just one of approximately 150 thaw-related landslides identified so far in the park. In several other places in the park, entire slopes have collapsed, leaving bare dirt exposed and sending patches of alpine tundra askew.
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Throughout the circumpolar North, thaw-induced slides are increasingly recognized as a public safety threat. A 2017 landslide that roared down a slope in Greenland — in a place where slides had not been previously known — triggered a localized tsunami that killed four people and destroyed 11 buildings in the fishing village of Nuugaatsiaq. In Alaska’s Glacier Bay National Park in southeast Alaska, a U.S. Geological Survey-led review of large rock avalanches unconnected to earthquakes found the risk doubled over the past three decades – a change concurrent with rising temperatures. On Banks Island in Canada’s Arctic, there was a 60-fold increase from 1984 to 2015 in landslides caused by thaw of permafrost ground ice, according to a study published in 2019. The study, by Antoni G. Lewkowicz of the University of Ottawa, examined more than 4,000 retrogressive thaw slumps, landslides caused by thaw in ice-rich permafrost. A surprise landslide emerged even near Alaska’s biggest city. A May 2020 slide that followed a period of sudden warmup gouged out a section of mountain slope near Alyeska Resort, a 40-mile drive south of downtown Anchorage.
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https://www.arctictoday.com/thaw-triggered-landslides-are-a-growing-hazard-in-the-warming-north/?wallit_nosession=1
