444 STUDIES FOR STUDEXTS 



awav the older lagoon and marsh deposits may be cited from unpub- 

 lished observations of ^Ir. I. Bo"^Tiian. Tliis is 2 . 5 miles south of 

 Scituate Harbor, IMass., between the third and fourth cliffs, where 

 the beach has retreated inland from 225 to 300 feet since 1898. 

 The beach ridge is of pebbles, from 100 to 125 feet wide at mid- tide 

 and from 8 to 10 feet above the level of the salt marsh behind it. 

 In consequence of the rapid retreat, the marsh material at present 

 shows at mean and low tide on the seaward side of the beach, illus- 

 trating the tendency of the sea to cut away the Uttoral as it advances 

 upon the land. 



There are a couple of ways, however, by which httoral deposits 

 may be preser\"ed upon a subsiding flat land. The first is illustrated 

 by the unequal beach-cutting obser\xd along the New Jersey coast. 



1^' Lagoor? cjeposil-s, mosHy liM-oral/ 

 i^^ Beach deposits, mosHy lithoral. 

 fS^ L'ndertoo) deposit-s. all mcvrine.. 

 1,2.^5^ Sra^e^. o^ toater level. 



Fig. 9. — Cross-section illustrating occasional preser\-al of Kttoral deposits by 

 building up of a beach, stages i and 2, without landward movement during land sub- 

 sidence. 



At Long Beach the sea has cut the lagoon space entirely away and 

 is fronted by bluff's. Farther southward the barrier beaches begin 

 and shut off Bamegat Bay. There is known to be a lateral transfer 

 of beach material southwestward along the Atlantic coast. By this 

 means it is possible for an off'shore beach to be built up vertically 

 as the coast subsides, the lagoon space behind broadening and deep- 

 ening, as sho^Ti in Fig. 9. Finally, when the lateral supply of 

 material ceases through recession of the bluff's, the beach \N-ill be 

 rapidly transferred inland, but the depth of wave-planation may not 

 reach to the bottom of the marsh deposits. 



Again, the shore '^'ill be more or less indented with shallow river 

 valleys turned into embayments or estuaries, and in these a greater 

 depth of httoral and estuarine deposits may accumulate, and partly 

 escape the marine transgression and planation which ensue with 

 further subsidence. The protective eff'ect T^ill be slightly diminished. 



