Submarine Valleys and Cafions off American Coast 
but it has not been sufficiently explored to give such complete details as are known in the Hudsonian 
Cafion. Adjacent to it amphitheatres dissect the continental border. Accordingly we may consider the 
submerged land forms here to be repetitions of those found elsewhere. 
Soundings show the deep embayment in the Continental Shelf heading towards Chesapeake Bay, 
into which both the Susquehanna and Delaware valleys enter. Here the Continental Slope is very much 
reduced in width, and the surface sands of the Shelf obscure the buried valleys ; which, however, the 
incomplete exploration, so far made, shows to exist, although the details cannot yet be furnished. 
In referring to the shifting sands, partly burying the more ancient valleys, it may be said that some 
of the sandbars occur below the present level of current action. These were formed during minor oscilla- 
tions, when the waters were shoal ; for changes of level are recorded in the more recent drainage channels 
over the surface of the Continental Shelf. 
Continental Shelves and Land-Tongues between the Southern States and the West Indies.—Off Cape 
Hatteras the Shelf is reduced to a breadth of 15 or 20 miles. Southward it, together with the 
lower plateau, widens to 300 miles in front of Florida. The Continental Slope descends steeply in all 
places, and precipitously in some, to more than 13,000 feet. The Shelf, to 450 feet below sea-level, 
extends south-eastward to the deeply dissected Bahama Banks and islands in front of Cuba and Haiti, 
although they are separated from Florida by the Straits of Florida, where the col rises to within 2100 
feet of the surface. Between the Bahama Banks and Cuba the col is submerged only 1800 feet. 
The Continental Shelf west of Florida has a width reaching to 150 miles. It is somewhat broader 
north of Yucatan. Were it not for channels crossing it, one reaching to 6400 feet, the Shelf would 
connect Honduras with Jamaica and Yucatan with Cuba. The Shelf has a considerable breadth on the 
southern side of the Caribbean Sea, but on its northern side, adjacent to the greater West Indian Islands, 
it is in many places reduced to a narrow fringe. The Lesser Antilles or Windward Islands surmount a 
very much dissected tableland, extending from the Greater Antilles to South America, which is cut 
through by one very deep channel. Throughout this region the outer margin of the Continental Shelf 
seems to be at a depth of less than 300 feet, beyond which the Atlantic slope plunges precipitously down 
to the ocean abyss. 
The outer and broader plains, in front of Carolina and Florida, are now submerged 2400 to 2800 feet. 
This same depth is repeated in a terrace adjacent to the Hudson Caifion, and also in steps in the Gulf of 
Mexico, and in the submerged land-tongues among the West Indian Islands. 
Lower than the surface of the Continental Shelf, the terrace plateaus are manifestly old coastal plains 
during a former moderate elevation of the land. 
Although the Blake Plateau in front of Florida and Georgia is swept by the Gulf Stream, yet this 
has not produced the planing down of its surface, for Pillsbury has found that the current is effective only 
to about 300 feet. At greater depths the current diminishes to zero before reaching the floor of the Straits 
of Florida. Indeed, a submerged valley is situated between two of the Bahama Islands, heading in 
Florida, and on either side of it higher ridges form the floor of the strait. Had the currents deepened the 
Straits, the lateral ridges of this cross-channel would have been planed down, and the main channel 
refilled with deposits. 
The repetition of plateaus observed at different points at similar depths in the northern regions has 
been especially emphasised by Nansen as evidence of changes of ocean-level. I believe to be of equal 
importance the similarity in depth below sea-level of many summits of the submerged land-tongues. The 
corresponding land features are low passes across mountain plateaus, where the atmospheric agents have 
lowered the valleys nearly to the level of no erosion. The minor variations in their height depend upon 
the breadth of the ridges dissected and the changing character of rock structure. 
The Submerged and Submarine Valleys of the Southern States.—F or a considerable distance from the coast, 
the Continental Shelf is covered with sand, thus burying the channels coming from Carolina and Georgia. 
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