Ocean salt water is primarily created through a two-pronged process: the erosion of rocks on land and the release of minerals from the seafloor.
Land-Based Erosion: The Major Contributor
The primary source of salt in the ocean is the erosion of rocks on land. Rainwater, slightly acidic due to dissolved carbon dioxide (forming carbonic acid), erodes rocks. This process, called chemical weathering, breaks down minerals within the rocks. These dissolved minerals, including salts like sodium chloride (common table salt), are carried by rivers and streams into the ocean. Over millions of years, this continuous process has accumulated vast quantities of salt in the ocean. USGS and NOAA both support this as the primary mechanism.
- Acidic Rain: The slightly acidic nature of rainwater plays a crucial role in this chemical weathering process.
- River Transport: Rivers act as conduits, transporting dissolved salts from land to the ocean.
- Accumulation Over Time: This process has occurred continuously for millions of years, resulting in the high salinity of ocean water.
Seafloor Hydrothermal Vents: A Secondary Source
Another contributor, though less significant than land erosion, is the release of minerals from hydrothermal vents on the ocean floor. These vents release heated, mineral-rich water from the Earth's interior. Some of these minerals contribute to the ocean's salinity. While less prominent than land-based erosion, this process adds to the overall salt concentration in the ocean.
Evaporation and Salt Concentration
While not a source of salt itself, evaporation plays a critical role in increasing the concentration of salt in the ocean. As seawater evaporates, the water molecules leave behind the dissolved salts, leading to a higher concentration of salt in the remaining water. This is the principle behind the traditional method of producing sea salt: allowing seawater to evaporate in shallow ponds. Reddit explains this simple process.
Conclusion: A Continuous Cycle
The salinity of ocean water is a result of a continuous process involving the weathering of rocks on land, the release of minerals from the ocean floor, and the concentration of salts through evaporation. This dynamic equilibrium maintains the high salt concentration we observe in the world’s oceans.
