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How did early ocean water become salty?

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Map graphic showing the boundaries of the five oceans-Pacific, Atlantic, Indian, Arctic, and Southern-using color-coded regions. Four different map projections are included: North Pole view, South Pole view, International Date Line view, and Greenwich Meridian view, each displaying the oceans' extents around the continents. — ocean Earth's oceans and their marginal seas cover nearly 71 percent of the planet's surface.

The salinity of the ocean is primarily the result of a long-term process of mineral accumulation from the land and volcanic activity.12

As rain falls through the atmosphere, it absorbs carbon dioxide, becoming slightly acidic. This water flows over the landscape, physically and chemically eroding rocks and dissolving minerals, including salts. These dissolved substances are then transported by rivers and streams into the ocean.12

Once in the ocean, the water undergoes the water cycle: while water evaporates from the surface, the dissolved salts are left behind, leading to a gradual increase in concentration over millennia. Additionally, hydrothermal vents and undersea volcanic activity contribute further minerals directly into the seawater. While some minerals are removed through biological processes or by becoming sequestered in seafloor deposits, the ocean has functioned as a steady-state chemical system for millions of years, maintaining its characteristic salinity.1234