The ongoing landslides in Rancho Palos Verdes, California, which accelerated in 2023, have sped up and slowed multiple times, including a particularly fast period last fall.

Heavy winter rains in the area in 2023 seeped into the soil and started a new landslide complex in certain Rancho Palos Verdes neighborhoods close to areas where ancient landslides had occurred, the city explains in an FAQ on the matter.

As of Wednesday, the landslide complex had slowed down by about 3% since early December, Rancho Palos Verdes officials said in a release. One of the landslides, the Abalone Cove slide, is continuing to slow down, while the Portuguese Bend landslide is continuing to move at the same steady pace it has had since the end of October.

Parts of the Palos Verdes peninsula have been on the move for over 60 years, according to NASA.

NASA’s Jet Propulsion Laboratory measured the landslides using advanced imaging technology on four flights last year between Sept. 18 and Oct. 17, and the agency found that the land, especially portions farther from the ocean, was moving as much as 4 inches per week, the agency said in a release last week.

“In effect, we’re seeing that the footprint of land experiencing significant impacts has expanded, and the speed is more than enough to put human life and infrastructure at risk,” NASA Jet Propulsion Laboratory scientist Alexander Handwerger said.

Town officials note that dry weather and a program of groundwater-removing wells has helped slow the slide.

“While JPL’s radar imagery strongly visualizes this dramatic acceleration and expansion of the landslide area during September and October 2024, the City would note that the landslide has decelerated since October due to the drier weather conditions and the City’s installation of highly productive deep dewatering wells,” town officials said in a release Friday.

The dewatering wells have removed more than 125 million gallons over their lifetime so far.

• Brad Matthews can be reached at bmatthews@washingtontimes.com.