Several processes contribute to ocean salinity. Increased precipitation decreases salinity by adding freshwater in the form of rain or snow. Increased evaporation increases salinity by concentrating the salt. In addition, precipitation leads rocks to undergo weathering and erosion, which release dissolved salts and other minerals. The dissolved salts ultimately enter the ocean over time. Underwater volcanoes and mineral-rich waters released through cracks on the seafloor are also sources of dissolved salts.