A “monster” sinkhole larger than any seen in southwest Oregon in 20 years forced the closure of a span of coastal highway this week.

The Oregon Department of Transportation cordoned off the five-lane stretch on Thursday after the formation of a sinkhole that measures 80 feet in diameter.

“It’s a monster for sure,” said Jared Castle, Oregon DOT spokesman for southwest Oregon. “This is a very unusual event and is a sinkhole of a magnitude that we don’t see but once every couple decades.”

Thursday’s void emerged next to another sinkhole that measures 50-feed wide. It will take an estimated 65,000 cubic yards of material to fill the holes and shore up the adjacent slope, he said.

Kyle Rice, a local drone hobbyist, uploaded multiple aerial videos of the holes to YouTube.

The new sinkhole is the largest seen in southwest Oregon since 1996. A sinkhole that formed early one November morning that year swallowed two tractor-trailers, plunging them 50 feet below the road they were on that dark night. No serious injuries resulted.

The same was true on Thursday: No one was injured and no cars were swallowed by the new void, which opened up in a parking lot between the Fireside Diner and a Chevron gas station, along U.S. 101 in Harbor, Oregon.

The original sinkhole opened up on Dec. 13 after a period of heavy rain and has swelled to its current size from an initial depth of seven feet and width roughly the size of a volleyball, Castle said. Crews have been working to clear a resulting blockage in an underground drainage, which has forced water flows to find another way to the sea from the nearby hills and thereby created other such voids, he added.

“Basically it’s like flushing a bunch of Legos down your toilet,” Castle said.

Sinkholes have proven to be an unpredictable problem for local authorities throughout the world, forming suddenly and wreaking havoc. The formation of a sinkhole resulted in the closing of a stretch of road in Washington, D.C., on Friday.

This post has been updated.

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