CHAPTER Ix 
BY JOSEPH WILLIAM WINTHROP SPENCER, M.A., Pu.D., F.G.S.A. 
The Submarine Valleys and Cajfions off the American Coast 
EXPLANATION TO ACCOMPANY PLATES X ano XI 
COPE of Investigations.\—The following pages contain a short account of the more important 
submarine valleys and cafions which dissect the Atlantic margin of the American Continent. 
These valleys are the continuations of those on the land, crossing the Continental and Island 
Shelves and their bordering platforms. The lower stretches of the continental valleys are 
now partly refilled with deposits, the character of which has been found by borings. Analogous 
physiographic forms have been studied in the high plateau regions of Western America, where great 
cafions within cafions, and amphitheatres or short steep valleys, dissect the border of the tablelands. 
In the submerged land-tongues connecting the islands important features are found. 
The study of all of these features shows that there have been great changes of level of land and sea, 
the occurrence of which is confirmed by the. distribution of mammals, plants, etc. Their investigation 
forms a new branch of sub-oceanic physiographic science. It is the counterpart under the sea of 
the land forms to which the term Geomorphology is applied. It includes the investigation of the 
Continental Shelves, submarine cafions, flooded and buried river-valleys, land-tongues, and even some 
basins. 
Development of the Study of Sub-Oceanic Phystography bordering the Continents.—Passing over the earlier 
recognition of the Continental Shelves, we come to the time when their forms were first systematically 
studied in their relation to the valleys indenting them. 
In the navigational soundings leading seaward from New York Harbour erratic depths were 
found. These “holes” were regarded by Professor J: D. Dana (since 1863)” as indicating a continuation 
of the Hudson River Channel. They were then known only to a depth of 720 feet where the adjacent 
sea-floor was submerged to half this amount. These “holes” awakened the interest of Mr. (now 
Admiral) Colby M. Chester, while he was in charge of the surveying ships of the United States Coast 
Survey, who caused a scientific survey of them to be made by Mr. (now Admiral) Willis Bronson. Soon 
afterwards these soundings were used by Professor A. Lindenkohl to show that the deep gorge reached to 
2800 feet below the surface of the sea. Years subsequent to this, I found from other soundings, made by 
Captain Z. A. Tanner, that a true cafion reached to a depth of 4000 feet.? All of us have regarded this 
Hudson Cajfion as evidence of changes in the level of the land and sea. 
Sir William Dawson (before 1872) had called attention to the deep fjord of the Saguenay (125 miles 
below Quebec) as also being evidence of change of level.! Professor George Davidson called attention to 
the similar submarine valleys off the Pacific Coast.’ In 1889 I made a fuller study of the submarine 
‘1 In the following pages Professor Spencer uses the term “Continental Shelf” for “Continental Platform” of Professor Hull in the previous 
pages, also “Slope” and “Declivity ” are synonymous terms.—Ep. 
2 Manual of Geology, 1st edition. 3 Geog. Fourn., London, Feb. 1905. 
4 Can. Naturalist, Montreal, vol. vi. (1872). 5 Proc. Cal, Acad. Sci. 3rd ser. vol. i. (1897). 
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