OCEANS AND LAKES 



271 



QUESTIONS 



1. How may the fact that a given beach grades regularly from 

 coarse gravel at one end to fine sand at the other be explained ? 



2. Why is there generally a larger percentage of elliptical 

 pebbles along beaches than along stream beds? 



3. (1) What was the origin of 

 the long, narrow peninsula shown 

 in Figure 286? What is it 

 called ? Why does it not extend 

 entirely across the bay? (2) 

 What is the prevailing direction 

 of the littoral currents along this 

 shore? How is it shown? (3) 

 Account for the triangular 

 marshy tract on the northeastern 

 side of the bay. (4) What seems 

 likely to be the future history of 

 the bay ? What are the several 

 agencies which will assist in 

 bringing it about? 



4. Plate XV. (1) Where 

 along this shore is erosion in 

 progress ? (2) Is deposition any- 

 where in progress? (3) What 



is the probable explanation of FIG. 286. Map of Morro Bay, coast 

 the irregularities of the coast line of California, 



in the vicinity of Devil's Slide ? 



(4) Why are parts of the coast high, and other portions low? 



(5) What was the probable origin of the island off San Pedro Point ? 



(6) Explain Lake Mathilde and Laguna Salada. (7) What changes 

 may be expected in the character of this coast line in the future ? 



5. What inferences may be made from the fact that the beach 

 lines of certain extinct lakes are not horizontal ? 



6. (1) Why is the ocean salt ? (2) Why are broad, shallow lakes 

 more likely to become salt than deep, narrow ones ? 



7. The size of certain salt lakes is decreasing. Does it follow 

 (assuming that the climate remains the same) that these lakes 

 will finally dry up? 



8. Account for the fact that borings about salt lakes have often 

 shown layers of salt alternating repeatedly with layers of clay. 



9. Are the waters of coastal lakes that are separated from the 

 ocean by bars generally fresh or salt ? Why ? 



