Submarine Valleys and Canons off American Coast 
In its descent the great chasm crosses two plateaus, one at 2700-3000 feet and the other at 
5000-5500. Beyond the cafion section the valley opens into the great Hullian Embayment of the Con- 
tinental slope.!. The cajion and submerged valley of the Hudson River has been explored to a depth of 
7500 feet below sea-level, where the valley is bounded by ridges 1200 feet in height. The cafion is 
double—the outer one being about 4 miles wide and 1200 to 1500 feet deep; the inner gorge is 
perhaps little more than a mile wide with a farther depth of 2800 to 2500 ects 
If we go to plateau regions, such as those of Mexico, short indentations may be seen in their 
borders, formed by streams of little length or perhaps by only rain-washes. In this manner the submarine 
Hudson cafion and adjacent borders of the plateaus have their walls dissected by short tributaries or 
amphitheatres, a name applied to such features seen at the Grand Cafion of Colorado, with gradients of 
200 to 500 feet per mile. These amphitheatres when closely situated soon lead to large embayments. 
All of these features are well developed in the edge of the Continental Slope or Declivity adjacent to the 
Hudson Channel. 
The sea-floor of the Hudsonian Channel is covered with sand, clay, or, farther down the Slope, 
with ooze. On Long Island and in New Jersey there are some drift accumulations, with underlying 
and unconsolidated Tertiary and Cretaceous clays, sands, and marl. From their thickness, found on the 
continent adjacent, it does not appear that the formations—Cretaceous to recent—can exceed 3000 feet. 
At Fort Monroe, near the seashore, some 300 miles to the south, these formations have a thickness of 
only 2000 feet, below which the drill reached crystalline rocks. Farther back, on the mainland, are 
Triassic sandstones, slates, and igneous rocks. From such evidence it may be inferred that the lower 
part of the submerged cafion of the Hudson River has been principally excavated out of crystalline rocks, 
although these may have been covered by Tertiary deposits, for samples of such have been brought 
up by dredges operating farther eastward.! 
From the character of this deep valley—having an outer and an inner cafion, winding in sharp turns, 
with its floor interrupted by abrupt steps, and its lower reaches opening out into a broad embayment 
with more gently sloping banks; having associated tributaries and the amphitheatres dissecting the 
submerged plateaus, or terrace steps of the Continental Slope—one cannot fail to regard this series of 
features as due to atmospheric and river erosion during changes of level of land and sea. Nothing has 
been found suggesting other than the complete analogy between physiography of this valley, although 
now submerged to a mile and a half or more, and the great cafons of our higher Western plateaus, even 
if these inductions conflict with speculations or prejudices against great changes of level at a late date, 
though smaller oscillations are readily conceded, or greater ones in more ancient times. 
It may be added that the surfaces of the Continental Shelves show evidence of other minor oscillations, 
belonging to a later date, not mentioned here. 
Submerged Valley and Cation of the Gulf of St. Lawrence-—The Gulf of St. Lawrence, the scene of my 
earliest studies, occupies a broad depression between the Laurentian Mountains to the north, composed 
of crystalline rocks, and the extension of the Appalachian Mountains to the south, with their old 
Palaeozoic shales, sandstones, etc. It is a submerged river-valley, the floor of which is covered by 
drift deposits. Even so far up as a point 100 miles below the city of Quebec, the open depth reaches to 
over 300 feet and the breadth is 13 miles. At 125 miles below Quebec the St. Lawrence River 
receives the Saguenay fjord with a depth of 882 feet, which farther down is partly refilled with 
moraine or delta deposits. At a point 50 miles below the Saguenay the open depth reaches 1200 
feet, and, beyond, a great valley traverses the Gulf of St. Lawrence. South of the island of Anticosti 
it is 30 miles wide, with the depth increasing to 2000 feet below sea-level. It is bounded by 
escarpments steeply rising 800 feet above its floor, and more gently to greater heights. The greatest 
1 This indentation is sufficiently large to be shown on small oceanographic maps, and leads to much greater depths than are fully 
explored. It received not only the Hudson cajfion, but others from the north, such as that from the Connecticut River. I named it after 
Professor Hull, who has interpreted similar features off the coast of Europe. 
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