Monday morning, at about 10 a.m., a large rock fell from the bluff and landed on Zimovia Highway, around 8-mile. Lt. Bruce Smith, with the Wrangell Police Department, said that it was only one rock initially, but when it landed it broke up into lots of pieces. Nobody was hurt in the rockslide, he added.
The debris blocked both lanes of traffic for some time. Smith said that he and others who got to the scene early were able to clear the road enough for people to drive on through. The Department of Transportation came out shortly thereafter to clear the rest of the highway. Everything was back to normal by noon, he said.
Sam Dapcevich, PIO for the Department of Transportation, provided a statement on behalf of Regional Engineering Geologist Mitch McDonald, regarding the rockfall. McDonald wrote that rainfall by itself is often not enough to cause a rockfall like what occurred on Zimovia Highway. He said that the effects of water runoff are "highly localized and have to be carefully inspected to determine their role in the failure." McDonald went on to state that the rockfall at 8-mile was a block failure in a jointed mass of rock, not a traditional landslide which is often caused by heavy rain.
"Sometimes these block failures are caused by a combination of rain and wind if large trees are growing on top of the rock-cut," the statement reads. "Tree roots can exploit open fractures in the bedrock, and in high winds, the movement of the trees can create leverage through the roots along the open joints of rock blocks. If rain wets the joint surface with sheet flow, winds leverage tree roots against the block, and the rock block is bound on all sides by dilated joints caused by natural erosion processes, then these conditions can combine to induce a block failure such as this recent event. I don't know if this was the failure mechanism without a close examination of the site, but the mechanisms are typically multi-faceted, making them unpredictable."
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