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Tide-gauge records from southern Mexico, the Caribbean Islands, and Central and South America that span the interval 1940–1970 reveal long-term changes of relative sea level according to regression analysis and eigenanalysis. The results indicate such large variations in both direction and rate of secular movement as to rule out changes in volume of ocean water as being more than a subordinate factor. The only satisfactory explanation is that the land level beneath the tide gauges is rising in some places and sinking in others.

Relative sea levels recorded by tide gauges during the past century in northern Europe are dominated by isostatic readjustment of the land following the latest deglaciation of Scandinavia and Scotland. Maximum relative uplift of the land is centered near the northern Gulf of Bothnia (at a rate of 6–7 mm/yr), with a smaller secondary maximum over Scotland (also at a rate of 6–7 mm/yr). Although there probably is a relaxing peripheral bulge surrounding the regions of maximum uplift, such a former bulge is poorly defined by coastal tide gauges; in the North Sea evidence for sinking of a former peripheral bulge of glacial origin is complicated by post-Carboniferous basin deepening with sediment loading and possible rejuvenation associated with glaciation. Other data (gravity, radiocarbon, geomorphology) support the interpretation that glacial isostasy controls the structure of relative sea-level change. Included in this pattern of relative rise of land is a eustatic signal that biases the estimates of glacial rebound. Such a eustatic signal could not be isolated from the isostatic signal using the present data, but glacial isostasy clearly is a major control for relative sea levels of the region.

About 2000 large sediment samples were collected during the early 1960s throughout the continental shelf off the Atlantic coast of the United States to establish and map sediment types including sediments relict from times of glacially low (and subsequently higher) sea levels. In about 510 of these samples we found fossil shells of mollusks remaining from environmental conditions different from those at present. Publications and collections by others contain about 70 additional samples having relict mollusks. Some of these shells indicate lower sea levels, others colder water, and still others warmer water than is now present. Radiocarbon measurements from earlier studies by us and others established the dates of colder water (late Pleistocene), and we made additional measurements to learn the dates of warmer water (about 1000 to 2000 yr B.P.). The results show reasonably enough that continental shelves are the sites of relict faunas as well as of sediments that indicate changed and complex environmental histories.

A brief description is given of the charts of the Pacific Ocean that have been published in various countries after World War II. These charts have become progressively better as the number of soundings has increased. Latest is a new bathymetric chart of the entire Pacific Ocean compiled by G. B. Udintsev and his associates at the Institute of Oceanology, Academy of Science, U.S.S.R. It has a 500-meter contour interval for the sea floor and land (plus a — 200 and a + 200-meter contour), and it has color tints for most contour intervals. Soundings from all available sources are incorporated: expeditions of Soviet oceanographic ships and those of other countries, plus data from hydrographic charts of many countries. The topography presented by the chart is more realistic than that shown by most other charts of the Pacific Ocean (Monaco, Japanese, U.S. Navy—world map), owing to the denser sounding network and the better cartography. Only the contours of the large-scale chart of the northwestern Pacific Ocean by Hess and of the general chart of the Pacific by Menard are comparable, and only the hachures and symbols on the large-scale chart of the northeastern Pacific Ocean by Menard yield a clearer impression of physiographic details

About 23,000 km of continuous precision echo sounding profiles supplemented by about 15,000 km of less precise profiles were compiled for the eastern Mediterranean Sea. Examination of the profiles reveals the presence of a long sinuous ridge that rises to depths shallower than 2500 m. This feature, the Mediterranean Ridge, is bounded on both sides by steep escarpments that lead down into trenches. The trenches north of the ridge, named Strabo Trench and Pliny Trench, have little fill, owing probably to insufficient supply of sediment. On the south side of the Mediterranean Ridge is the Herodotus Abyssal Plain, about 1200 km long. South of this plain is a broad gentle slope of the Nile Cone that spreads out from the Nile Delta.