The slide on one of America's most picturesque highways took place on Saturday morning in a remote and largely uninhabited area known as Mud Creek.
The road in that section of the highway had already been shut down before a million tons of earth came tumbling down from a hillside, burying a 1,500-foot (nearly half a kilometer) section of the highway, said Jim Shivers, a spokesman for the state's transportation agency.
"We're looking at a road closure of several months," he said. "This is a very, very big event... and it's something that we really haven't seen before. We have a lot of work to do."
He said the scale of the slide was such that the wall of rock and dirt that cascaded down the slope continued down to the ocean floor 250 feet off the shoreline.
California experienced one of its soggiest winters this year, which caused a number of mudslides, floods and numerous road closures along the winding coastal road.
In March, a stretch of the highway near Big Sur was shut down after the Pfeiffer Canyon Bridge collapsed, spelling economic disaster for the region that heavily relies on tourism.
The rockslide at Mud Creek took place about 30 miles (48 kilometers) south of Pfeiffer Canyon, meaning that two sections of the highway have now being shut down, Smith said.
Although the rough winter weather is over, the ground is still saturated and shifting in many areas.
Smith said crews had been out doing repair work at Mud Creek but were ordered out of the area a week ago because of small slides that were taking place nearly everyday.
"We were concerned that there would be a slide, we just didn't think it would be of this size," he said.