Large slabs of rock slid down and covered the main road on the lower half of the mountain, between Split Rock and Sphinx Rock, late Wednesday, according to a news release from the park. A security officer discovered the slide shortly before midnight.
Workers used heavy equipment to move two of the boulders Thursday morning. Dynamite will be used to get rid of the rest of the large boulders.
The road has been reopened to one-way traffic, and Grandfather Mountain remains open.
"Seeing a rockslide this time of the year is not a big surprise," Kate Scharer, geology professor at Appalachian State University in Boone, said in a statement. "Small ones can be seen along many roadsides in the High Country right now."
A rough winter is probably to blame for the rock slide, Scharer said. Ice likely formed in cracks of the rock, loosening it. When warmer temperatures and heavy rain melted the ice, the conditions were set for a slide.