Published:January 01, 1972
The first method of exploring the ocean floor and mapping its sediments was the use of tallowed lead weights at the end of sounding lines. Seamen often cast the lead on approaching land during fog, and when they encountered a large area of shallow mud bottom, known as the “Block Island soundings,” between Martha’s Vineyard and Long Island, they knew their position along the coast (Pour-tales, 1871, 1872). The general characteristics of many samples taken with lead line by ships belonging to the Coast and Geodetic Survey were described by Pourtales (1871, 1872), and their content of foraminifers was reported by Pourtales (1850) and Bailey (1851, 1854). On the basis of 9,000 such samples, Pourtales (1870) compiled the first general bottom-sediment chart of the continental shelf for the area between Cape Cod and Key West. Notations of the character of the bottom also were written on field sheets and published navigational charts, and they were used by Shepard (1932) in a general study of the distribution patterns on continental shelves, particularly those of the Atlantic coast of the United States. During World War II these notations also were used for making large-scale bottom-sediment charts to help estimate the probable ranges for acoustic detection between submarines and surface ships. Charts were made by the United States Navy under the direction of H. C. Stetson and also by the German Navy (Oberkommando der Kreigsmarine, 1943).
Figures & Tables
Western North Atlantic Ocean: Topography, Rocks, Structure, Water, Life, and Sediments
The Atlantic coast of North America was the first part of the New World to be described by maps and texts; its exploration begain with the Vikings nearly a thousand years ago. Since then, the pace of exploration of both land and ocean floor has increased steadily. The concern during the 1960s was with details of geology, water, and life that largely were bypassed during earlier stages of discovery and exploration. The accumulation of knowledge was expressed approximately by the publication of charts, articles, and tabulations of data. This publication is concerned with the Atlantic continental margin of the United States, and it necessarily includes some information about the adjacent land and ocean areas. It is a summary of the existing knowledge of the ocean floor, the water above it, and the life that is in the water or at the bottom. The chapters contained within the publication fall into seven categories: Physiography, Rocks, Structure, Water, Life, Sediments, and Origin of Continental Margin.