Engineers are looking into what caused a landside and cliff collapse near Long Beach.
A large section of road that had been closed since September collapsed into the ocean Sunday in San Pedro.
Signs were posted, warning residents to stay away from the unstable area near the White Point Nature Preserve.
The landslide was moving at a rate of 4 inches per day, according to city engineers.
"My greatest concern is that all these homes are going to end up in the water, and that we're going to be separated like our own little island," one resident said.
Sunday's slide caused powerlines to sway along the nearly 900-foot section of road between South Western and South Weymouth avenues.
No injuries were reported and no structures were threatened.
A bluff collapsed in Encinitas in January, taking the stairs leading to the beach with it.
In December 2010, a landslide carried away about 100 linear feet of hillside next to a College Area home. The ground slipped down into the canyon.
A tourist from Las Vegas was killed by a bluff collapse along Torrey Pines State Beach. The same stretch of beach saw a similar collapse a year later.
In October 2007, the earth on Mount Soledad suddenly opened up and threw the lives of dozens of residents into turmoil.