SUBMERGED PLAIXS OFF EASTERN COAST OF AMERICA 



merged plains, and is not their limit, as is popularly stated ; but this ^ 

 line shows frequent cove-like indentations or culs-de-sac. For 250 miles \ 



eastward of Cape Cod peninsula the sunken plains maintain their gen- 

 eral monotonous characteristics, being submerged from 200 to 250 feet 

 with a fringing border covered by an additional 200 feet of water ; but 

 north of this submarine peninsula is the broad valley of the gulf of Maine, 

 traversed by channels from the direction of the Kennebec, Penobscot, and 

 Saint Croix rivers, besides that from the bay of Fundy, showing sound- 

 ings from 720 to 1,080 feet, without reference to the coves or gulfs into 

 which they enter. This region is one of drift deposits, which may give 

 irregularity to the submarine topography, and probably accounts for the 

 obstruction of 200 feet to the valley. South of Nova Scotia this conti- 

 nental border is broken into hills and valleys, showing the remains of 

 typical coastal plains dissected by deep valleys. Between cape Breton 

 and Newfoundland is the Laurentian valley, which will be noticed later. 

 Beyond are the great banks of New^foundland, extending 300 miles south- 

 east of that island. Here is a remarkable repetition of the features of 

 the coastal plains of the continent, largely represented by extensive flats 

 submerged only 200 to 250 feet and forming a plateau elevated 150 to 250 

 feet above a lower plain. It is entirely separated from Newfoundland 

 by a broad channel in depth corresponding to the lower plain. In both 

 cases the soundings indicate channels from 60 to 200, and, in some cases, 

 to 300 feet in depth, incising their surfaces. These banks appear to 

 have had the same relationship to Newfoundland that the plains of New 

 Jersey now have to the mountainous zones behind them. 



Evidence of channels similar to those of the Newfoundland banks 

 may be found everywhere on the submerged plains, which are mani- 

 festly continuations of the present land surfaces, but the}'' are apt to be 

 obstructed by sands carried b}^ the currents or by drift deposits ; but 

 these features will be brought out in studjdng some of the great river 

 channels. 



Hudson River Channel 



Its character was recognized by Professor James D. Dana as long ago 

 as 1863,^ but the features were not full}'- known until 1891, when Mr A. 

 Lindenkohlf made use of the accumulated soundings and show^ed that 

 the drowned channel of the Hudson river is clearly traceable across the 

 submarine shelf of the continent. He says that it is first noticeable 12 

 miles southeast of Sandy Hook, at a depth of 120 feet below the surface 



♦Dana's Manual of Geology, 1863. 



t Am. Jour, Sci., ser. iii, vol. xli, 1889, pp. 489-J99, and Report U. S. Coast Survey for same year 



