Finding the fault

Geologist Tyler Ladinsky explaining the fault line in the rock formations at Montara State Beach. He will be speaking to the Half Moon Bay History Association. Jamie Soja / Review

The Half Moon Bay History Association is delving billions of years into the past while also taking a peek into the future with a presentation devoted to the Coastside’s unique geology. 

“Rocks and Shocks” will kick off about 6:15 p.m. on Tuesday, Dec. 5, at the Portuguese Cultural Center on Kelly Avenue in Half Moon Bay. The presenter, Tyler Ladinsky, is both a Half Moon Bay resident and a professional geologist working in San Mateo. 

Ladinsky will be offering a closer look at the local fault lines and how they shaped the Coastside. 

“San Andreas typically gets the credit and a lot of the spotlight,” Ladinsky said of the fault line responsible for the infamous 1906 San Francisco earthquake and, more recently, the Loma Prieta earthquake of 1989. 

Less famous, but closer to home, is the San Gregorio fault that cuts right along the coastline and comes up onto shore at Año Nuevo State Park and at Pillar Point. 

“The San Gregorio fault is a pretty major feature in the plate boundary between the North American and Pacific plates,” Ladinsky said. 

During Tuesday’s presentation, Ladinsky plans to discuss the complexity of the fault line and how it has influenced the surrounding landscape. For example, the fault line is responsible for Princeton’s low elevation contrasted against the uplifted area along Moss Beach and the Pillar Point bluffs. 

The unique geologic forces are even responsible for rocky shoreline structures that make them such good locations for finding rock cod and other marine life. 

Ladinsky says he plans to discuss previous events on the San Gregorio fault line as well as potential for future temblors. 

“It’s certainly an active structure that’s shearing between major plates,” Ladinsky said. 

Like the majority of California’s fault lines, the San Gregorio fault is of the strike-slip variety, meaning that the fault surfaces rub against each other horizontally. 

Ladinsky adds that there is a vertical component to the fault line as well that provides for the shifts in elevation along the coastline. 

Ladinsky, who grew up in Southern California, first became interested in geology while getting a close look at the geologic features from the vantage point of a surfboard. The geologist says that the Coastside is a good place for people interested in the earth sciences.  “It’s a geologic Disneyland, so to speak.” Ladinsky said. 

The doors for Tuesday’s event open at 5:30 p.m. for snacks and refreshments.

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