The Source of Sea Salt

The ocean is salty primarily due to the runoff from rainwater that weathers rocks on land, carrying minerals and salt into rivers and ultimately the sea. This process accumulates salt in the oceans since they have no outlet like lakes do. Rainwater, which is slightly acidic, reacts with carbon dioxide, and this contributes to the dissolution of these minerals, notably salt, which then flows through streams into the ocean. As a result, the saline concentration in the ocean reaches about 35 parts per thousand, making it much denser than freshwater, which also explains why people find it easier to float in the sea.