Submarine Valleys and Cafions off American Coast 
In Cuba, Jamaica, and Barbados, beneath the superficial limestone, are deposits of oceanic ooze 
forming a marl, which, when wet, tends to move. For example, on the eastern side of Barbados is a broad 
amphitheatre in the capping limestone. After a protracted rain, in 1901, hundreds of acres of the under- 
lying marl began to flow, thereby undermining and widening the embayments in the surface limestone. 
It was still moving when last visited by myself, eighteen months after the great rain-fall. Oceanic oozes 
logically should underlie the Bahama Banks, and at no great distance away such are found at the south- 
eastern end of Cuba. Their occurrence would fully explain the broad character of the deep channels 
among the Bahama Banks capped by harder strata. 
The Lesser Antillean or Windward Banks and their Valleys.—The most eastern of the Greater Antilles 
is the island of Puerto Rico, but from it a submarine plateau, surmounted by islands, extends in a crescent 
form to South America. It has a maximum breadth of a hundred miles, but farther south the natural 
frontal plains seem to have been washed away into the Atlantic, leaving only a few remnants (such as the 
eastern plains of Guadeloupe and the mass of Barbados) ; so that the ocean rolls against the chain of 
Pleistocene and modern volcanic islands. 
Southwards from the plateau of the North-Eastern Islands, a submarine spur, surmounted by the Aves 
Banks, extends southward in the Caribbean Sea, but this does not reach to South America. 
The steep slopes of the volcanic and other islands have their surfaces trenched with deep ravines, and 
these may be followed by soundings across the island shelves to the embayments in the Continental 
Slopes. 
Many of the smaller islands rise from larger separated plateaus, now mostly submerged to inconsider- 
able depths in the shallow seas. These are dissected by the beginnings of cafions and valleys which 
extend to thousands of feet below sea-level. In many cases their walls are almost precipitous. Their 
characteristics are in no wise different from those indenting the border of the Continental Shelf or that 
of the high plateaus of Mexico. 
Between the larger islands are channels with a breadth of 20 to 40 miles. The one between the 
Grenadines and South America is broader, but here the Continental Shelf extends seaward some sixty 
miles, and approaches the southern extension of the island shelf. The summits of the land-tongues between 
the islands are submerged to no more than 2000 to 2400 feet, except between Martinique and the 
islands on either side, where the depth reaches 3500 feet below sea-level. Barbados surmounts an out- 
lying mass, with the land-tongue, between it and the main chain of islands, submerged to a depth of 
5500 feet. ; 
The broad channels belong to an earlier period than the deep valleys and cafions. They resemble 
‘the lower breaches in denuded tablelands, broadened, after submergence, by wave action. Their origin 
is somewhat more complex in the vicinity of the volcanoes, where limited areas of the sea-floor have been 
locally raised. Nevertheless, the character of the dissecting cafions and valleys has not been materially 
altered thereby. : 
While such is the general character of the Lesser Antillean Plateau, all the way from South America 
to the Virgin Islands, this last group is dissected by the deep Anegada Passage, between St. Croix and 
St. Thomas, islands of the Virgin group, where the summit of the land-tongue is depressed to 6400 feet 
below sea-level. This is the great physiographic break between the Lesser and Greater Antilles. The 
depths between Haiti and Cuba, and Haiti and Jamaica, are a little less, while the channel between Cuba 
and Yucatan has exactly the same depth as that between the Virgin Islands. It cannot be too strongly 
insisted upon, that the submerged passes from Haiti and Cuba directly to Central America, on one side, 
and, on the other, by way of the Windward Islands, to ‘South America, are now at equal depth beneath 
the surface of the sea. 
1 See papers on the Geological and Physical development of Antigua, Guadeloupe, Anguilla, St. Martin, St. Bartholomew, and Sombrero ; 
Dominica; Barbados, etc., Q.F.G.S. vols. lvii. lviii. (1901-2). 
27, 
