SAND DUNES AND SALT MARSHES 



and subsidence of the land, whereas in reality 

 there had been all the time a subsidence. 



The evidence of the sinking of the land 

 seems to me plain, but why is not the salt 

 marsh drowned too, or rather why is there 

 any salt marsh formed at all? As the land 

 sinks and the water rises it would be easy 

 to picture the gradual extension of the sea 

 into the land, the waves lapping the shore, 

 all the time reaching higher and higher, until 

 even the old glacial hills were overflowed. 

 This would certainly be the condition of 

 things if the marsh did not build up as fast 

 as the land sank, and the upbuilding can be 

 seen in all the zones of the marsh. 



Everywhere in the creeks and estuaries, 

 shut out by the sand dunes from the impact 

 of the waves of the sea, forests of waving eel- 

 grass flourish and entangle the fine sediments 

 in their meshes, and help build up this zone. 

 When the sand brought in by the tides and 

 storms has accumulated in shallows so that 

 these flats are sufficiently exposed at low 

 water, the thatch grass claims it, and entraps 

 the finest mud among its stalks. Into this 

 the grass from its hollow stems sends out 

 higher and higher roots, and the whole be- 



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