Ocean. History of water and the Earth’s crust

Abstract

Views on the origin and evolution of water (the amount and mode of incorporation into crustal and mantle rocks) on Earth are quite diverse. To substantiate them, arguments from various sections of geography, geology, geochemistry, cosmochemistry, and cosmogony are used. A comprehensive analysis allows us to fairly confidently assume that the appearance of water is associated with the final stage of the formation of the planet, which began after the accumulation of 60—90 % of its volume. This period coincided with the entry of water-bearing carbonatites,among other chondrites,into the accretion zone. Having estimated their contribution to the formation of water from different sources, we can compare it with the geological and geophysical data on the Earth’s early history. For this purpose, the author’s idea of the global asthenosphereas a relic of an ancient magmatic ocean, was used. The framework made it possible to estimate the volume of matter from which the emergence of a magma ocean made it possible to extract water. The synthesis of these independent results allows us to state quite confidently that water to fill the ocean was available (in one form or another) throughout the entire studied geological history of the planet. The problem of the ocean itself (a deep-water reservoir with a crust different from the crust of the continents — less powerful and more basic) is considered mainly using the well-known results of B.A. Bluman and E.M. Rudich on the oceans and M.I. Budyko and co-authors on the continents. Their conclusions agree with the schemes of deep processes in the ocean tectonosphere considered by the author. These processes are controlled by a series of geological phenomena and anomalies in geophysical fields.The processes are reduced to heat and mass transfer in the eugeosyncline superimposed on the anomalously basic continental crust and subsequent activation.Thus, a fairly definite picture of the formation of the modern ocean due to the previous development of the Earth’s tectonosphere in the Mesozoic-Cenozoic is emerging.