Hypsometry of ocean basin provinces

Abstract

The frequency distribution of depths in ocean basins has been determined using the most recent American and Russian oceanographic charts as sources and a computer for data processing. Data have been complied for individual ocean basins and marginal seas, and also for nine different physiographic provinces, including, for example, ‘ocean basin,’ ‘rise and ridge’ and ‘continental shelf and slope.’ The summary result differs little from a hypsometric curve drawn by Murray and Hjort in 1912. Considering both land and sea, by far the most common levels are approximately at sea level and at about 5 km, the general depth of ocean floor. The compilation by physiographic provinces leads to a new understanding of the hypsometric curve, even though it does not change the shape. The distribution of depths in the ocean basin province is singly peaked and symmetrical. The distribution in the rise and ridge province is similar, but the mean depth is about 1 km less. This can be interpreted as indicating that one province is merely the elevated equivalent of the other, a conclusion which generalizes the field observation that some localized oceanic rises and ridges are formed by ephemeral bulges in the mantle under a normal oceanic crust. Most occurrences of depths between sea level and the deep sea floor have been produced by the formation of rises and ridges rather than by the deposition of sediment derived from continents. The development and collapse of rises and ridges may have caused substantial fluctuations in sea level during geological time.