As Houses Slide Into Canyon, City Needs Answers Fast

A homeowners association in Southern California is trying to hire a geologist—quickly. A landslide that began Saturday night destroyed 12 houses in the city of Rolling Hills Estates and has sent others slowly slipping toward a canyon, the Guardian reports. No one is sure why, so the city told the HOA to bring an expert in to figure out the cause of the ground's shifting, a process that the mayor has found opaque so far, which she said is making her feel more anxious about the situation. Until officials and residents receive expert answers, a county supervisor said, "There's nothing we can do, I've been told, to stop what's happening." Janice Hahn added that everyone is waiting—"waiting for the homes to fall."

The city council declared an emergency Tuesday night, and Los Angeles County and California governments might receive similar requests. Residents were given 20 minutes' notice to evacuate on Saturday night; by Sunday, 10 more houses on the Palos Verdes Peninsula were moving as the ground beneath them shifted, per KTLA. Another 17 were being checked in the city, about 30 miles south of Los Angeles. The ground had moved 20 feet in 24 hours. On top of that, the moving earth broke a sewer line on Tuesday, which caused five more houses to be evacuated. Hahn said the land is shifting quickly. "You can actually hear the snap, crackle and pop every minute when you're there," she said.

Houses that once lined Peartree Lane are almost hidden now, per the Los Angeles Times, having slipped below the previous elevation of their driveways. Many suspect the heavy rain the area endured from late last year through early this year is behind the slide. A geological sciences professor at Cal State Long Beach said the factors that can lead to a landslide are "the steepness of the hillside, the underlying rock type that's underneath that hillside and the water saturation in the rocks or the soil." Nate Onderdonk added that "the topography, the steepness doesn't really change that fast and neither does the rock type, so it's really got to be something to do with the water." (More landslide stories.)