The process of salination likely began soon after the oceans formed but took hundreds of millions of years to reach the salinity levels similar to what we see today. The oceans were likely significantly salty by about 3.5 billion years ago.

Salinity increased primarily through the weathering of rocks and the leaching of minerals (including salts) into the water. Rivers and streams carried these salts into the oceans. Volcanic activity also contributed ions to the seawater. Over time, as water cycled through evaporation and precipitation, salts became more concentrated in the oceans.

By about 2.5 Billion years ago, the oceans were likely had salinity levels similar to modern oceans.