ANCHORAGE, Alaska — A few years ago, Ronald Daanen was driving north of Coldfoot on the Dalton Highway, looking for drunken trees.
He pulled over when he saw some tipsy spruce on a hillside.
The University of Alaska Fairbanks scientist thought the tilted trees would be a classic sign of thawing permafrost, ground that has remained frozen through the heat of at least two summers. But these trees were part of something larger — a giant tongue of moving hillside that was oozing toward the Dalton Highway.
When covered in snow, the mass looks like a glacier covered with trees, but it’s not a glacier. Nor is it a rock glacier, a mass of rock and ice that slowly slips down mountains (there are several in the Alaska Range and the Wrangells).
Permafrost scientists have found three of them close to the road near Coldfoot and have seen several more along the highway south of Atigun Pass. Using Google imagery, they have found many more in the same area. Retired USGS geologist Tom Hamilton saw the same features as he mapped the geology of the area in the 1970s. Hamilton called them “flow slides.” Daanen and Guido Grosse of the University of Alaska Fairbanks’ Geophysical Institute are calling the features “debris flows.” In a paper they recently co-wrote, the scientists describe the phenomena as “an unusual form of mass movement.”