Firefighters responded to a call for a cliff-side rescue near the 800 block of Palmetto Avenue at about 5 p.m., North County Fire Authority spokesman Matt Lucett said.
A 13-year-old boy had been climbing on rocks near the beach when a large boulder came loose, trapping him and crushing his legs, Lucett said.
Using hydraulic rescue equipment, firefighters took about 90 minutes to lift the boulder and extricate the boy.
He was taken to San Francisco General Hospital with serious injuries.
