According to the Office of Naval Research, saltwater is denser than freshwater due to the weight of the salt it contains. Rocks, such as granite, and minerals with low levels of sodium are released by constant water erosion.
The loose salt content is swept along to the ocean where it remains, although most of the water evaporates into clouds that produce rain. According to the Encyclopedia Britannica, saltwater, in the form of oceans and seas, covers 70 percent of the Earth's surface. Seawater is approximately "95.6 water, 2.5 percent salts" mixed in with "inorganic and organic materials," and a few atmospheric gases, such as chlorine.