ROLLING HILLS ESTATES, Calif. >> A landslide tore apart luxury homes on Southern California’s Palos Verdes Peninsula on Monday, leaving a confused jumble of collapsed roofs, shattered walls, tilted chimneys and decks dangling over an adjacent canyon.

The slide in the Los Angeles County city of Rolling Hills Estates began Saturday when cracks began appearing in structures and the ground. Twelve homes were red-tagged as unsafe, and residents were given just 20 minutes to evacuate.

The pace of destruction increased through the weekend and into Monday.

“It is moving quickly,” said Janice Hahn, chair of the Los Angeles County Board of Supervisors, who represents the area. “You can actually hear the snap, crackle and pop every minute when you’re there as each home is shifting, is moving.”

It was initially believed that all of the red-tagged homes were sliding, but Assistant City Manager Alexa Davis clarified Monday afternoon that 10 were actively moving. An additional 16 were being monitored but had not required evacuation, Davis said in an email.

The cause of the landslide was not known. But a fissure running among the homes raised suspicion that this past winter’s heavy rains may be involved, Hahn said.

“We won’t know until a geologist and a soil expert really does a post-op on this and tells us what happened,” Hahn said. “But because of that fissure, the initial thinking is that it was because of the heavy rains that we had last year and all that underground water has caused this. But we don’t know.”

Hahn said many of the displaced residents were unsure whether they were insured for such loss, including one who moved in two months ago after escrow closed. The county assessor was to meet with the residents to tell them they could apply for property tax waivers.

“My heart goes out to these people,” Hahn said. “We gave them 20 minutes Saturday night to evacuate and get their things. Obviously they didn’t get everything.”

Damaging landslides have occurred previously on the Palos Verdes Peninsula, which rises high above the Pacific on the county’s south coast and offers residents spectacular views of the ocean and greater Los Angeles.

A landslide that began in 1956 destroyed 140 homes in the Portuguese Bend area of the city of Rancho Palos Verdes, and earth continues to move there. The slide coincided with construction of a road through the area, which is atop an ancient landslide.

Among other notable earth movements on the peninsula, a 2011 slide severed the blufftop ocean road near White Point in the San Pedro section of Los Angeles several months after engineers began noticing cracks and fenced off the area for study.

Southern California’s complex landscapes contribute to landslides, according to an overview by the U.S. Geological Survey in conjunction with the California Geological Survey.

Some of the many potential factors include earthquakes, steep slopes, sedimentary soil that is not rock hard, and water percolating down into the earth after heavy rains, the report says.

Human-induced landslide factors include construction without proper grading of slopes, alteration of drainage patterns and disturbances of old landslides.