Sinkholes: Their causes and effects in Alaska

Published: May. 27, 2022 at 9:29 AM AKDT
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FAIRBANKS, Alaska (KTVF) - In May 2022, a large sinkhole opened up on an easement off of City Lights Boulevard, creating a hazard for people living in the area and potential problems for their properties.

Sinkholes, like those seen across Alaska, come as the result of a long geologic history.

20 to 40 thousand years ago, permafrost formed underground throughout the Fairbanks area and across Alaska. This ubiquitous permafrost lasted until about 10 thousand years ago, when changes to the climate caused much of the permafrost to melt.

According to Yuri Shur, Professor at the University of Alaska Fairbanks (UAF) Engineering Department, big ice wedges remain underground at spots across the Interior. When these ice wedges melt, cavities form underground. Then all it takes is running water to expand the hole before the ground above gives way.

Sinkholes have been seen in the Fairbanks area in the past, from the Goldstream area to UAF’s Troth Yeddha campus.

However, it is impossible to predict where exactly a sinkhole will form. “We can predict the big area in which these sinkholes can be formed, but we cannot say specifically about the site,” said Shur.

Sinkholes tend to form during the summer months, and are more likely to occur after a large amount of snowmelt, which the Interior experienced this spring.

They also tend to happen at higher elevations and on sloped ground. “Any slopes around Fairbanks can still contain some old ice wedges, or be potential places of sinkhole formation.”

When new homes are constructed, the holes drilled into the earth to detect permafrost can often miss the smaller ice wedges. “You cannot drill holes everywhere.”

The City Lights sinkhole also lies near an electrical pole, causing added worries for the area. “It’s important for people who maintain this easement and want to have a right-of-way on this easement to maintain it and to check it,” said Shur.

Proper drainage can help keep water from causing underground erosion.

But once formed, the only way to treat a sinkhole is to fill it with soil. If left untreated, Shur said these sinkholes will continue to expand in area.

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