Geologic Trips, San Francisco

Lands End

 

The small islands and rocks seen along the shoreline east of Ocean Lookout Park represent hard blocks of serpentine, basalt, chert and sandstone that have been eroded from the soft clay matrix of the City College mélange. The melange was formed along the zone of thrusting between the rocks of the San Bruno Mountain terrane and the Marin Headlands terrane while the rocks were in the Franciscan subduction zone. The fine clay matrix of the melange was formed from rocks that were thoroughly ground up by the thrusting. The blocks in the melange are pieces of hard rock that survived the grinding. Wave erosion along the bluff at Lands End has washed away much of the softer clay matrix and left behind the hard rocks seen in the photo.

Related Links

Geologic background:  San Francisco (pdf)

Geologic trips:   Alcatraz Island        Cliff House        Fort Point         Golden Gate         Lands End      

 

Exterior Websites

Golden Gate National Parks Conservancy:  Lands End     Lands End Lookout

Wikipedia:  Lands End

From Lands End looking northeast toward the Golden Gate.