CAPE COD GEOLOGY 



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landed here in November, 1620, has ever since remained a convenient port of 

 refuge in storms because of its safe approach from the north and west and its 

 outlying position. A depth of more than 20 fathoms is found off the west side 

 of the Cape as far around as Wood End, close to the shore. Between Long Point 

 and Provincetown the harbor has a depth of 9 fathoms, and surveys made by 

 the Coast and Geodetic Survey * show that this depth is maintained by the tides 

 and currents. 



There are no inlets on the outside of the Cape north of Nauset Harbor, 

 which is a crooked passage into Town Cove at Orleans and which is subject to 

 the encroachment of a bar that is working southward. (See Plate l). The bays 

 and inlets near Chatham and north of it may be reached from the sea through 

 a shifting entrance across a bar. No bar of the coast is more subject to changes 

 in the position of beaches and bars than that near Chatham. The inside passage 

 from Chatham northward to Pleasant Bay is shoal and is navigable at low water 

 by boats of small draft only. 



On the south side of the Cape there are several small ports, such as those at 

 Hyannis and Woods Hole, which meet local needs. They are all due to irregu- 

 larities in the deposition of the glacial material either in the plain, as at Hyan- 

 nis, or in the frontal moraine, as at Woods Hole. 



Below Provincetown, on the Bay side of the Cape, there are two harbors, 

 one at Wellfleet and the other at Barnstable. That at Welmeet is due to a 

 break in the continuity of the high glacial plain about Truro, on the north. 

 There appears to have been an unfilled area in the arm of the Cape between 

 this plain and the frontal moraine on the south, about Orleans. The water in 

 this area is shallow, and extensive shoals southwest of it require boats coming 

 from the north to make a long doubling to the south in order to enter the channel. 

 Barnstable Bay is formed by a barrier beach that lies off an incurved section 

 of the frontal moraine in which a shallow tidal inlet has been formed behind 

 the beach. The bottom of the bay on its south side is shallow and shelves off 

 gently to the 20-fathom line. At low tide the bottom is bared for half a mile 

 or more as a flat of sand and mud and, here and there, areas of washed glacial 

 gravel. Plymouth harbor does not strictly lie within the area of this report, 

 but it is directly connected in origin with the Cape Cod Bay glacial lobe. The 

 depression in the drift which the bay occupies appears to have been formed by 



1 H. L. Marindin, On the changes in the shore lines and anchorage areas of Cape Cod (or Province- 

 town) Harbor as shown by a comparison of surveys made between 1835, 1867, and 1890, U. S. Coast 

 and Geodetic Survey, Appendix No. 8 to Report for 1891. Part 2, pp. 283-288, with plates Nos. 11, 12. 

 See also Henry L. Whiting's report in Appendix No. 12 to the Report of the Coast Survey for 1867. 



