GLACIATION AND SUBMARINE VALLEYS*

Abstract

CONTINENTAL terraces are huge submerged benches, each surfaced by a continental shelf and a continental slope. The fall-off of shelf to slope begins not far from the 50-fathom isobath. The shelves vary in width from a few miles to 150 miles, their seaward gradient averaging about 1 in 1,500. The average gradient of the continental slope, measured from the fall-off to the flat plain of the deep ocean, is about 1 in 15, or 100 limes as steep ; measured from the fall-off to the 500 fathom isobath, the seaward gradient averages about 1 in 10, or 150 times as steep as that of the shelf.