The Deep-Sea Drilling Project is now engaged in a 30-month program extension which will take the drilling vessel Glomar Challenger to the Atlantic, Pacific, and Indian Oceans. Drilling sites have been selected by advisory panels established by JOIDES (Joint Oceanographic Institution Deep Earth Sampling). During the first 18 months of operation the program directed its effort to testing the hypotheses of sea-floor spreading

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and continental drift, sampling old sediments, and recovering a complete sedimentary section for paleontologic reference. Drilling on the mid-ocean ridge system in relatively young (Tertiary) sediments was extremely successful. Every site drilled with the intention of testing sea-floor spreading has substantiated the hypothesis. Almost complete Cenozoic sedimentary sections have been recovered in both the Atlantic and Pacific Oceans. Attempts to recover the oldest sediments in the oceans have been thwarted by the inability to penetrate chert layers that appear to be ubiquitous in the deep basins. Drilling throughout the first 18-month program was undertaken without the ability to withdraw the drill string and reenter the same hole. The capability to reenter the hole is anticipated ear y in the program extension and will be instrumental in the success of the proposed future drilling program. The emphasis of the new program has shifted from the mid-ocean ridge system to the deep basins where the oldest sediments may be sampled and to the continental margin to investigate the interaction of the mobile sea floor and the continental masses.

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