As with the other nearby lakes in the southeast portion of the Point Reyes peninsula , Pelican Lake occupies a natural synclinal depression formed behind blocks of rock displaced by landslides within the past 10,000 years . The depressions forming Crystal , Pelican and Bass lakes appear to have been caused by the Double Point Slide , which covers an area of about . The rocks involved in the landslide are shale , chert and sandstone , some similar to Miocene rocks of the Monterey Formation and others to Pliocene rocks from the Central Coast Ranges . The process that caused these slides is ongoing , with several nearby slides caused by the 1906 San Francisco earthquake and others as recently as 1956
1906 San Francisco earthquake
1906 San Francisco earthquake
Pelican Lake (Marin County, California)