Mathematics – Logic
Scientific paper
May 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agusm.u23a..01b&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #U23A-01
Mathematics
Logic
3616 Hydrothermal Systems (0450, 1034, 3017, 4832, 8135, 8424), 8413 Subduction Zone Processes (1031, 3060, 3613, 8170), 1836 Hydrological Cycles And Budgets (1218, 1655), 3025 Marine Seismics (0935, 7294), 3060 Subduction Zone Processes (1031, 8170, 8413)
Scientific paper
"We all live on this water planet which we have mistakenly chosen to call Earth" (Anon.) When viewed from outer space, the dominant feature of the earth's surface is the abundance of liquid water. Liquid water has been present at and near the earth's surface for most of its history, and has made it possible for life to develop, evolve and survive on the third rock from the Sun. In recent years it has also become clear that the earth's interior represents an important storehouse for water and that water in the deep earth exerts a major influence on the geochemical and geodynamic evolution of the planet. The largest near-surface water reservoir is the oceans, containing 13,400 x 1017 kg of H2O, or about 97.3% of all water at and near the earth's surface. The major geological reservoirs for water can be divided into the oceanic and continental crust, the upper and lower mantle, the transition zone and the core. The core has been estimated to contain up to 100 times the amount of water in the earth's oceans, in the form of hydrogen in high-pressure iron alloy (Williams and Hemley, 2001, Ann. Rev. Earth Planet. Sci., v. 29: 365-418). In the upper and lower mantle and the transition zone water is present mainly as trace and minor amounts (101 -" 104 ppm) in nominally anhydrous phases. Even though the concentrations are low, the absolute amount of water in these mantle reservoirs may be very large given their relative contributions to the total mass of the earth. Thus, the upper mantle is estimated to contain between 1,230 and 3,693 x 1017 kg of H2O, the transition zone between 4,481 -" 89,613 x 1017 kg of H2O, and the lower mantle between 34,200 and 68,500 x 1017 kg of H2O. Assuming even the most conservative estimates for the amount of water in these geologic reservoirs, the amount of water in the oceans and other near-surface reservoirs is dwarfed by that contained in the geologic reservoirs. The conventional hydrologic cycle describes the movement of water between the various near-surface reservoirs. Similarly, water moves between the geologic reservoirs to define a geohydrologic cycle, although the fluxes between reservoirs are poorly constrained. Perhaps the most important environment in which water moves from one geo-reservoir to another is in subduction zones, where water from the subducting oceanic slab (composed of oceanic crust and upper mantle material) is transferred to several reservoirs, including the oceans, continental crust, oceanic crust, upper and (possibly) lower mantle, and the transition zone. Approximately 1.01 x 1012 kg of H2O is subducted per year. Of this amount, 9 x 111 kg is returned to the oceans by updip flow. The remainder is transported to greater depths and incorporated into the various mantle reservoirs. The major environments in which water from geo-reservoirs is returned to near-surface reservoirs are arc volcanoes and the mid-ocean ridge hydrothermal systems. Approximately 0.35 to 1.05 x 1011 kg of H2O is transferred from the deep crust and upper mantle and returned to the atmosphere per annum from arc volcanoes, while 1.2 x 1011 kg of magmatic (mantle) H2O is returned to the oceans as a result of submarine volcanism. Fluxes between the other deep-earth reservoirs are model dependent and at present are poorly constrained.
Azbej T.
Becker Sebastian
Bodnar Robert J.
Cannatelli Claudia
Fall Abdoulaye
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