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c.o.o.l. fact #1 If all the oceans were to evaporate, the salt left behind would cover the entire planet with a layer of salt that was 50 meters (half a soccer field) thick.
c.o.o.l. fact #2 Ordinary table salt (NaCl) is the most common of sea salts. One source of salt in the ocean is the hydrothermal vents on the seafloor that spew mineral deposits from beneath the ocean floor.
c.o.o.l. fact #3 Another compound found in sea water is limestone or calcium carbonate (CaCO3). Limestone is the main component of sea shells and coral reefs. The ocean's movement wears down shells and reefs and releases the calcium carbonate which is then absorbed by the ocean.
c.o.o.l. fact #4 The salinity of the ocean is not uniform across the planet. Where the weather is hot and dry, more sea water is evaporated leaving salt behind and very little rain occurs to replenish the ocean. The Red Sea and the Mediterranean Sea have the highest salinity level of 40 - 41 ppt (parts per thousand) versus the average of 35 ppt.