FIGURE 4-2 



ESTIMATES OF SEA LEVEL RISE WORLDWIDE (1961-1973) 



YEARS BEFORE PRESENT 



8 6^2 



5568 1/2-LIFP 



5750 1/2-LIFE 

 5 _.is 



Estimates by various geologists as to the worlds sea level over the past Holocene Epoch. The 

 dominant cause of change is climatic, although tectonics and compaction effects are also 

 involved (from Davis 1985). 



polar ice sheets. Within the long-term pattern, short-term fluctuation in sea level, including 

 temporary regression, occurred in response to shifts in climate and glacial movements. Overall, 

 however, a period of rapid eustatic sea level rise, lasting about 4,000-5,000 years, accompanied 

 the melting of Pleistocene glaciers. During this period, river valleys and adjacent coastal areas 

 were drowned and marsh vegetation developed inland, but not extensively as long as sea level 

 continued to rise rapidly. Thereafter, sea level rise slowed to near zero, but has continued 

 gradually throughout, creating conditions favorable for marsh development and long-term 

 accretion at rates equaling or exceeding sea level rise (Emery and Uchupi 1972, Redfield 1972, 

 Davis 1985). 



During the period of rising sea level, opposing isostatic uplift of the land surface in response 

 to reduced glacial overload has occurred in some places, at rates sufficient to cause emergence of 

 subtidal areas despite the rising sea level (Holmes 1965). Elsewhere (e.g., The Netherlands), land 

 subsidence reinforces sea level rise effects. Typically, sea level records report only net heights that 

 incorporate land surface movements. The relative significance of isostatic and eustatic effects is 

 spatially variable; but in New England, based on carbon-14 dating of marsh peat, eustatic sea 



90 



