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CAPE COD GEOLOGY 



long-shore drift of sand toward the entrance to Nantucket Sound. Professor 

 Henry Mitchell of the United States Coast Survey has shown by a comparison 

 of several surveys, dating from 1784, that this point had receded 1,400 feet by 

 the time of the survey of 1874. 1 



The changes on the north shore of Nantucket have been less in recent years. 

 The sand flat built out in front of the old sea cliff known as Sherburn bluffs is 

 fairly ancient. The lighthouse at its east end, at Brant Point, was first erected 

 in 1746, but beacon lights were maintained there by the inhabitants as early as 

 1700. 2 



Before 1700 Copaum Pond, on the north coast, was a small port open to the 

 sea, and on its shore was made the second settlement on the island. A great 

 storm filled the entrance with sand, whereupon, in about 1720, the inhabitants 

 moved to the present site of Nantucket. A curious relic of the ancient play of 

 the tides in Copaum Pond may be seen in a small sandspit on its eastern shore. 



Coatue Beach, whose remarkable cusps face the inner harbor, appears to 

 occupy a position determined by Coskata Island, a small tract of glacial deposits 

 just north by west of Haulover Break. The other beaches here mentioned derive 

 their sand from the longshore transportation of material derived from cliffs on 

 one or another side of them, but Coatue Beach appears to be composed, as 

 Gulliver has suggested, 3 of sand that has been carried along the east coast of 

 Nantucket around Great Point and then southwestward. Shaler 4 suggests that 

 part of the sand of Coatue Beach may have been derived from the bottom of 

 Nantucket Bay and that part of it may have been derived from Great Head. 

 Evidence that Coatue Beach once did not exist is found in an old sea cliff on the 

 west side of Coskata Island, where now a small lagoon is enclosed by beach sand. 

 Before the beach at Great Point or Coatue Beach had been formed, when the 

 sea bathed the base of Sherburne bluffs, the east coast of Nantucket, from Cos- 

 kata or Wauwinet southward, must have stood farther east, and the north 

 coast, from Coskata southwestward, must have lain west or southwest of the east- 

 ern headland. The beach at Great Point, which extends into the sound as a 

 wing thrown off from the present eastern headlands from Squam to Sankaty, is 

 probably working westward with the recession of the headlands upon which it 

 depends, and it and Haulover Break are probably marching inward with the 

 continued recession of their supporting headlands, and the breaches in the Haul- 



1 Mitchell, Henry, Monomoy and its shoals, Mass. Harbor and Land Commissioners' Report for the 

 year 1886, Public Document No. 11, p. 42, Boston, 1887. 



2 Douglas-Lithgrow, R. A., Nantucket, a history, p. 279, New York and London, 1914. 



3 Gulliver, F. B., Nantucket shore line, Bull. Geol. Soc. America, 15, pp. 521-522, 1904. 

 1 Shaler, N. S., Geology of Nantucket, U. S. Geol. Survey Bull. No. 53, p. 51, 1889. 



