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Using a new temperature recording instrument recently developed at the Woods Hole Oceanographic Institution, downhole temperature measurements were made at five sites during Deep Sea Drilling Project Leg 86. The instrument, which can be installed in the shoe of the hydraulic piston corer, allows measurements of sediment temperature to be made simultaneously with the collection of sediment cores. A numerical procedure was applied to correct the temperature disturbance caused by the corer's friction with the sediment. Detailed temperature profiles constructed from the data were combined with the measurement of thermal conductivity to calculate heat flow. Heat flow values were generally low at all sites of Leg 86, consistent with the age of the lithosphere (> 100 m.y.) in the Northwestern Pacific Basin.

A marine geophysical study of the Andaman Sea has been conducted as part of the International Indian Ocean Expedition. A combination of magnetic, gravity, bathymetric, and sea‐floor heat‐flux measurements, seismic sparker reflection profiles, and bottom sediment samples has been used in a study of the seaward continuity of major subaerial tectonic trends. The data indicate positive continuity of the structural trend of the Barisan Range of northern Sumatra and the Burma Range. It was found that the central graben of the Barisan Range of northern Sumatra extends into the Andaman Sea north to latitude 10°N. A previously unreported interdeep has been observed between the outer sedimentary island arc and the inner igneous trend of the major primary arc which forms the western boundary of the Andaman Sea. Continental thickness of the crust is indicated under the sedimentary island platform. In the area of the backdeep, the north‐northeast trends of the Malaysian peninsula are prominent.

Deep ocean mining for manganese nodules is under development by several multinational mining consortia. Initial estimates of probable environmental effects of this mining were made before any actual operations were conducted. Recent pilot mining tests near Hawaii have provided an opportunity to verify and modify the initial estimates. The two principal initial impacts of mining are in the near surface water associated with increased turbidity caused by mining discharge, and in a relatively limited zone at the sea floor associated with collector traverse. Examples are presented of estimates of reduction in primary production in the turbid plume as well as the contrasting effect of increased nutrients. Effects of the mining collector on benthic populations are considered. The limitations of extrapolation of results obtained during pilot mining tests are discussed.

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