ABSTRACT
The ocean is about 4,000 MY-old. It is considered the largest habitat for life on Earth and produces about 40 % of the annual global primary productivity. The Theory of Plate Tectonicsexplains that continents move as part of lithospheric plates on top of the asthenosphere, due to underlying convection cells in the upper mantle.The most recent period of repeated glaciations (which occurred during the Pleistocene, beginning 2.6 MY ago and lasting until 11,700 yr ago) is explained by Milankovitch’s hypothesis for cyclical variations in Earth’s orbital parameters.After the Last Glacial Maximum, the melting of large ice sheets during the Holoceneproduced a net transfer of mass to the oceans. Holocene sea level rise formed semi-enclosed coastal bodies of water with an open connection to the ocean, known as estuaries, which have been adapting to shifting conditions to this day.The most elementary division of the oceans considers benthic and pelagic environments. The former are subdivided into depth zones, while pelagic environments have both horizontal and vertical divisions. The neritic zone comprises water masses over the continental shelf, while the oceanic zone is subdivided into depth-layers. The basis for these divisions responds to geological, physical, and chemical attributes.
