The earth is on the move in San Pedro, where a landslide is exposing huge, deepening crevices along a seafront roadway and dropping chunks of earth and concrete into the ocean below. The slide is not threatening homes, but it did forced the closure of a 900-foot stretch of Paseo del Mar between Weymouth and Western Avenues in September. And now, city officials say the landslide is getting more serious. In fact, city crews have begun building a fence around the crumbling 100-foot bluff in an effort to keep onlookers from getting dangerously close to the mass of land sliding toward the sea.