Sea water is not uniformly saline throughout the world. The planet's freshest sea water is in the Gulf of Finland, part of the Baltic Sea. The most saline open sea is the Red Sea, where high temperatures and confined circulation result in high rates of surface evaporation and there is little fresh inflow from rivers. The salinity in isolated seas (for example, the Dead Sea) can be considerably greater.
Composition of Earth's ocean water by element. Note that this is by mass, not molarity
| Element | Percent | Element | Percent
|
|---|
| Oxygen | 85.7 | Sulfur | 0.0885
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| Hydrogenhydrogen helium H Li Full table General Name, Symbol, NumberHydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1 , s Density, Hardness 0. 0899 kg/m3, NA Appearance colorless Atomic properties Atomic weight 1. 00794 amu Atomic radius (ca | 10.8 | CalciumSee also Calcium, New York, United States. potassium calcium scandium Mg Ca Sr Full table General Name, Symbol, Numbercalcium, Ca, 20 Series alkaline earth metal Group, Period, Block 2 (IIA), 4, s Density, Hardness 1550 kg/m3, 1. 75 Appearance silvery whi | 0.04
|
| ChlorineChlorine (from Gr. Chloros meaning "pale green"), is the chemical element with atomic number 17 and symbol Cl . It is a halogen, found in the periodic table in group 17. Chlorine gas is greenish yellow, is two and one half times as heavy as air, has an in | 1.9 | Potassiumpotassium calcium Na K Rb Full table General Name, Symbol, Numberpotassium, K, 19 Series alkali metals Group, Period, Block 1(IA), 4 , s Density, Hardness 856 kg/m3, 0. 4 Appearance silvery white Atomic properties Atomic weight 39. 0983 amu Atomic radius | 0.0380
|
| SodiumSodium is the chemical element in the periodic table that has the symbol Na Natrium in Latin) and atom number 11. Sodium is a soft, waxy, silvery reactive metal belonging to the alkali metals that is abundant in natural compounds (especially halite). | 1.05 | BromineBromine (from Gr. Bromos meaning "stench"), is a chemical element in the periodic table that has the symbol Br and atomic number 35. A halogen element, bromine is a red volatile liquid at room temperature which has a reactivity between chlorine and iodine | 0.0065
|
| MagnesiumMagnesium is the chemical element in the periodic table that has the symbol Mg and atomic number 12. Magnesium is the eighth most abundant element and constitutes about 2% of the Earth's crust, and it is the third most plentiful element dissolved in seawa | 0.1350 | CarbonAlternative meaning: Carbon (computing Carbon is a chemical element in the periodic table that has the symbol C and atomic number 6. An abundant nonmetallic, tetravalent element, carbon has several allotropic forms: diamonds (hardest known mineral). Bindi | 0.0026
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Ocean salinity has been stable for millions of years, most likely as a consequence of a chemical/tectonic system which recycles the salt. Since the ocean's creation, sodium is no longer leached out of the ocean floor, but instead is captured in sedimentary layers covering the bed of the ocean. One theory is that plate tectonics result in salt being forced under the continental land masses, where it is again slowly leached to the surface.
