Continental margin is assumed here to include the continental shelf, the continental slope, the continental rise, and other equivalent features in less mature margins such as marginal troughs, marginal plateaus, outer ridges, and continental borderlands. Petroleum industry's interest in continental margins is based on the same factors that delineate oil provinces on land: (1) zones of thick fine-grained sediment deposition with high organic content (source rocks); (2) lenses, layers, and wedges of sandstone (reservoir rocks); and (3) active tectonism to produce the necessary structure and to provide driving forces for the migration of petroleum into reservoirs. These factors occur in an area that encompasses more than 20% of the earth's surface area. If the shelves are co sidered to be regions of erosion and transport, the slopes and rises still occupy 10-15% of the earth's surface; this is an area larger than that of major onshore oil production. Present technology makes it possible to drill about 35% of the continental margin areas. Such projects as JOIDES and similar projects being planned can provide at least preliminary data on the remaining 65%. The advent of deep submersibles makes it possible for geologists to see the surface of the entire area as other techniques are used to probe beneath the surface.

Historically, the investigation of the margins began when the first measurement of water depth was made as an aid to navigation in shallow coastal water. However, the major contribution of modern workers can be restricted to the last 30 years in which the expansion of knowledge has been exponential. It is no exaggeration to say that the time necessary for the publication of these abstracts is sufficient to include new basic discoveries and interpretations. Thus earth scientists are in

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the scientifically fortunate position of being reduced to obsolescence as they speak.

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