Taking a walk along the Palos Verdes: a soft lesson in geology

At one time, Palos Verdes was actually an island—part of the Channel Island archipelago that today still comprises eight islands, including those off the coast of Ventura as well as Catalina, San Clemente and their neighboring islands.

You may have heard that Ranchos Palos Verdes is dealing with massive mud slides.

An ancient complex of landslides under the Portuguese Bend Reserve, located within the larger Palos Verdes Nature Preserve, was activated in 1956, which halted all housing development in the area. That allowed many of the homeowners to buy their properties for far less than what they would later be worth after undergoing extensive renovations.

For hundreds of years, the Portuguese Bend barely felt any movement from the gradually shifting landslide complex. But this year, residents living in the community’s 140 homes started to see cracks in the ground – in their closets, bedrooms and gardens – steadily getting bigger and ripping apart their properties as the land movement began to accelerate following two years of severe storms starting in 2022.

Officials say the land underneath Rancho Palos Verdes is moving at approximately 1 foot per week. And while it’s been moving slowly for thousands of years, construction in the mid-1950s greatly accelerated the slippage and the last two years of wet winters have only caused it to move more.

So, what is it about the land in this particular area that makes it so susceptible to slippage on a big enough scale to uproot homes and the families who live there? 

The biggest driving force behind the landslide? Water trapped in the ground.

The land movement happening in Rancho Palos Verdes is called a translational landslide — one that measures over a mile long and a mile wide. It’s tending to be more uplift than lateral movement, dropping vertically at the top and rising up at its toe.

To make matters worse, there are two landslides at play — the shallower one that initially caused red-tagging of homes and a stoppage of electricity, then a deeper one that’s moving even faster.

The shallow slide has been well-documented over the decades.  Its the deep slide that is of concern.  Its a large complex that seems to be moving as a unit.

How do you get the water out of the land to stop or limit the movement towards the ocean? Its a Herculean task. Will implemented measures to relieve the water pressure work? How much will it cost over a long period of time? Note – a land mass this large has been stabilized and documented.

dievca really experienced the landslide driving around the southern peninsular subregion – there was a portion of the road which had a drop — it looked and felt like going down a ski jump. Much more than a 45 degree angle. Whoa!