Water has great abundance on the Earth, and of that abundance about 97% is sea water. Sea water contains about 3.5% by weight of salt (sodium chloride). The salinity does vary, and the combination of salinity and temperature has a major influence on ocean currents and behavior. Salinity is a crucial property of the seas and is widely measured. Among the variouse ways to characterize the average salinity are 35 ppt (parts per thousand), 35 psu (practical salinity units). The typical range of salinity is about 33 to 37 ppt. About 70% of the Earth is covered with water. The salt in that water would build a 180 mile high, 1 mile thick wall around the equator according to the Windows to the Universe website.