Crews began clearing 23,000 tons of rock Sunday night that crashed onto state Route 108 between Viola and Altamont in Grundy County, Tenn.
The rock slide, which happened shortly after midnight Sunday, is expected to take about three weeks to clear.
Detour signs soon will be posted along the curvy two-lane mountain road. It's going to cost those who use the now entirely blocked road - mostly locals going to and from work - "a little bit of time," according to Tennessee Department of Transportation spokeswoman Jennifer Flynn.
"The whole face of the bluff just tipped forward. It just fell into the road and broke into several pieces," Flynn said Sunday night. "It's basically a hillside, and it fell off a bluff."
A Nashville geologist at the site estimated a single rock to weigh about 2,000 tons, and Flynn said crews are going to have to drill and blast some rocks multiple times before they're moveable.
Geologists don't predict another rock slide soon, but like predicting earthquakes, it's not an exact science.
"You know it's going to happen," Flynn said. "It might be 50 years from now, but eventually some of the rocks are going to come down."