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Basin, at the northern tip of the island (Mulliken, 1951) . 

 The most obvious changes to the topography of Plum Island 

 that can be seen today are the eroding Bar Head drumlin at 

 the southern tip of the island and the continuing 

 enlargement of the nearby Sandy Point. The growth of Sandy 

 Point has been well documented by Farrell (1969) and Jones 

 (1977) . 



CLIMATE 



Because of Plum Island's proximity to the coast the 

 adjacent ocean is an important moderating factor in its 

 climate. Climatological data was obtained from the nearby 

 Newburyport Pumping Station and from Rockport, Mass., which 

 is approximately eight miles south southeast of the southern 

 tip of the island (Climate and Man, 1941; Lautzenheiser , 

 1974, and PRNWR records). The average annual temperature 

 for this region is 50 F (10 C) with a January average of 

 29.4 F (-1.4 C) and a July average of 67.9 F (19.9 C) . 

 Average annual precipitation is 41.19 in (193.14 cm) with 

 the winter season being the wettest due to frequent storms. 

 There is usually very little snow accumulation on the 

 exposed eastern side of the backdune, for it is quickly 

 blown away. However, considerable accumulations occur on 

 the leeward western side of the backdune ridge, particularly 

 in the sunken forests. Winds are primarily westerly or 

 offshore. The storm winds on the other hand are most 

 prevalent from the eastern quadrant, with those most 

 important to beach formation coming from the northeasterly 

 direction (Mclntire and Morgan, 1964) . Jones (1977) feels 

 that high energy storms are an important mechanism in the 

 development and migration of the Plum Island barrier beach 

 dune system. 



GEOLOGIC HISTORY 



Plum Island began to form after the retreat of the 

 Wisconsin Ice sheet some 6,300 years ago (Mclntire and 

 Morgan, 1964) . Upon retreat of the glacier a complex series 

 of sea-land elevation changes took place. About 6,000 years 

 ago the land in this area began to subside while sea level 

 continued its eustatic rise. During this period deposition 

 of coastal sediments was greater than sea level rise and 

 Plum Island began to form (Mclntire and Morgan, 1964; Jones 



