San Francisco Bay and Golden Gate 153 



quent streams along the path offered by the Haywards fault, 

 and they thus become subsequent streams till they break 

 through the wall of the fault valley and again become conse- 

 quent streams. The Haywards fault occurred after the devel- 

 opment of the main fault between the Berkeley Hills block and 

 the San Francisco-Marin block. In a similar way the San 

 Andreas fault is related to the earlier San Bruno fault. The 

 San Bruno fault marks the southwest boundary of the San 

 Francisco-Marin block. The San Andreas fault occurred at a 

 later time. The San Andreas fault marks a long straight val- 

 ley for many miles across the Marin Peninsula north of San 

 Francisco. The long series of lakes along the San Andreas rift 

 valley represent the interrupted drainage down the steep south- 

 western slope of the San Francisco-Marin uplifted block, the 

 Buriburi Ridge. North of the Golden Gate the San Andreas 

 fault joins the San Bruno fault, which latter forms the south- 

 western steep wall of the San Francisco-Marin fault block. 

 The San Andreas fault is separated from the San Bruno fault 

 west of San Francisco. It is traced for 300 miles to the south- 

 east. Earth movements along the San Andreas fault caused the 

 earthquake of 1906. 



