90 



Adventures in Scenery 



sandstone was deposited and before the San Pablo was laid down. 

 Below, and older than the Briones, is the Rodeo shale (13), 

 which appears at the surface farther east. 





Sea 



Lave | 



FIG. 25. Cross section along the line C D in figure 24. 

 numbered as in figure 24. 



Formations 



The formations have been uplifted, squeezed or compressed 

 together into folds or arches (synclines and anticlines) , as have 

 the rocks in many places in California. Many faults or breaks 

 in the crust of the earth occur, the rocks on one side of a fault 

 or break being uplifted relatively to those on the other side. 

 Rocks of different ages may lie opposite each other on either 

 side of a fault. In figure 26 no less than 10 geologic formations 

 are crossed in a distance of 3% miles along the line A B. 

 The formations are cut by the Wild Cat and Pinole faults (F 

 and F') and by other faults of lesser extent. San Pablo Ridge 

 is capped by lava flows, the rocks of which, being hard, resist 

 erosion. Grizzly Peak and Bald Peak rise to altitudes of 1,759 

 and 1,930 feet respectively. It will be seen from the figure 

 that the lava rock forms the cap of the broad San Pablo Ridge, 

 and that this broad ridge is the top of a syncline. The eroded 

 edges of the formations outcrop on the slopes of the ridge. 



FIG. 26. Cross section along line A B in figure 24. Formations num- 

 bered as in figure 24. 



