Rancho Palos Verdes, a coastal town in the Los Angeles area, could be described as a geologically ticking time bomb.
The wealthy city sits atop sheer cliffs overlooking the Pacific Ocean, which has been slowly shifting and sinking for centuries.
Now, that movement is accelerating. In past years, the ground has slid downward at a rate of 8 inches each year, while in some places it has wobbled 13 inches per week between July and August.
The resulting landslides leveled beachfront mansions, collapsed roads and the utility company Southern California Edison was forced to cut power to about 250 homes to prevent fires.
“Eight inches a year is a measurable amount, and they had to make repairs to the road that crossed the area, but now it’s moving so fast they’ve had to close several roads, cut off gas supplies and cut off power,” said Eric Fielding, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “It’s crazy, but you can’t keep rewiring every week.”
In the Portuguese Bend neighborhood of Rancho Palos Verdes, 140 homes will be without power indefinitely, and in the Seaview section of the city, about 60 homes will be without power for a week or longer.
Governor Gavin Newsom declared a state of emergency in the city on Tuesday.
Experts say the situation is an unfortunate result of heavy rainfall over the past two years. The Palos Verdes Peninsula is made up of weak rocks and clay deposits that prevent water from flowing properly underground. So during periods of heavy rain or high tectonic activity, the cliffs can slide, turning the continuous, slow-moving landslides into catastrophic disasters.
It is not yet clear whether anything will be done to stop the land from moving.
“Basic physics tells us that once an object starts moving, it wants to stay moving,” said Jonathan Godt, landslide hazards program coordinator at the U.S. Geological Service.
The threat to Rancho Palos Verdes is not new. Scientists say the soil beneath the city has been moving for hundreds of years, but it was mostly stationary until a road construction project in the 1950s precipitated a landslide.
“The landslide was moving faster in the 1950s than it is today,” Fielding said, “but they were able to largely stabilize it by drilling wells and pumping water.”
However, heavy rainfall last year and at the beginning of this year caused the sliding speed to increase again.
Fielding said it was difficult to establish a direct link between landslides and climate change, but that rainfall had intensified as a result of global warming, meaning a warmer atmosphere could hold more moisture, increasing the likelihood of severe storms.
Godt said it was difficult to predict when major landslides would occur, despite the knowledge that heavier rainfall was more likely. After periods of heavy rainfall, it could take months or even years for water to saturate deep rocks and clay and cause the soil to deform.
It’s also difficult to predict which slow-moving landslides will become problematic. Landslides that move at glacial pace over hundreds or thousands of years are not uncommon in Southern California and around the world, Godt said.
“For most of these places, it’s not a problem in a human lifetime or even multiple human generations because it’s just a blink of an eye from a geological perspective,” he said. “But there are situations where a series of heavy rainfall events or shaking from earthquakes or other geological processes happening under our feet set these landslides moving again.”
Rancho Palos Verdes is already facing setbacks in potential efforts to mitigate landslides. The city said it discovered an even deeper landslide that was active in the area last month. Officials said the movement, deeper than 300 feet, was too fast and too far underground to dig drains and pumps to remove water.
Following the emergency declaration, Rancho Palos Verdes Mayor John Cruikshank said the allocated money would go to the city government and landslide prevention efforts, but not to individual homeowners.
Cruikshank told a local CBS affiliate on Wednesday that homeowners whose power is cut off will need to spend tens of thousands of dollars or more to switch to off-grid alternatives such as solar and battery technologies. He hopes the state will help cover such costs.
Cruikshank added that residents are already liable for damage to their homes because typical home insurance policies do not cover landslides, and hundreds of landslides occur in California each year.
Tim Kelly, a mechanical engineer who moved to the Rancho Palos Verdes neighborhood in Portuguese Bend 30 years ago, said he now relies on solar panels for power and remains in his home. He attended a public meeting Tuesday where residents begged city officials for a solution.
“We are resilient,” Kelly said of the community. “We are not going anywhere.”
Kelly said other homes in her area have shifted on their foundations, some properties have cracked and broken into sections, but her home has remained stable. She added that she and her neighbors will not leave their homes and will wait for government leaders and scientists to figure out the best way to “stop the slide.”
Kelly said the local government has failed for decades to come up with long-term solutions to prevent water from saturating the canyon and diverting it to the ocean. Now, the problem is coming to a head for the city, and time is of the essence.
“The patient is sick and something must be done to bring him back to life,” Kelly said.
This article was originally published on NBCNews.com