A landslide deposited dirt, rocks and uprooted trees on the Seward Highway south of Anchorage Monday morning, shutting down the road for hours as crews cleaned up the debris.
The slide happened near Mile 105, roughly a mile on the Anchorage side of Indian in the Windy Corner area, said Shannon McCarthy, a spokeswoman for the Alaska Department of Transportation and Public Facilities.
The debris swept across both lanes of the highway, took out a portion of the guardrail and then spread over the railroad tracks. Crews measured the debris pile at 75 feet wide and four feet deep. On its website, the transportation department called it a "major landslide."
The slide started around 5:50 a.m., the department said.
It closed both lanes of the highway for more than five hours, temporarily cutting off the only road that links Anchorage to the Kenai Peninsula.
McCarthy said she was not aware of injuries from the slide.
Crews did find "crunched up car parts" in the debris, she said. Someone may have driven through the area just as the slide started or tried to navigate the debris pile right after it ended.
"We really caution the public to never drive through a slide," she said. She said people should report debris on the road and then "go back to a safe area."
McCarthy described the slide as "highly unusual" for this specific area on the highway. She said it was the first time the department had an issue with a landslide in that location.
While rockfalls occur on the highway, it's unusual for treed areas — like the slope near Mile 105 — to slide, she said.
She said the transportation department believes the slide was triggered by the freeze-thaw weather.
Temperatures in the area were unseasonably high last week, reaching into the mid-40s, according to the National Weather Service. Then temperatures dropped below freezing Sunday and into Monday morning.
"There's a lot of water flowing underground in this area," McCarthy said. The freeze-thaw "caused some instability and that made it slide."
McCarthy said the department would continue to study Monday's landslide.
She said drivers should expect intermittent lane closures as the department replaces the 150-foot stretch of damaged guardrail.
Tim Sullivan, a spokesman for the Alaska Railroad, said it did not appear that the slide damaged the railroad tracks. Trains were not scheduled to travel in the area Monday morning.