After up to 8 inches of rain, a 200-foot-long stretch of U.S. 441 slide down a slope Wednesday morning on the North Carolina side of the 500,000-acre.
The National Park Service said the initial assessment shows about 90,000 cubic yards of soil slid about the length of a football field and is piled 45-50 feet deep.
There were no injuries in the landslide.
As park officials watched on Wednesday, debris continued to fall.
The National Weather Service predicted snow for the mountains Thursday and Thursday night.