What causes ocean waters to be salty while most inland lakes are not?

The ocean's saltiness is due to dissolved salt and other minerals, such as sodium, chloride, sulfate, magnesium, and calcium. When water flows over rocks, it picks up these minerals and carries them downstream to the oceans. The cycle of evaporation and precipitation of water is what causes the concentration of salt to increase over time. As water evaporates from the ocean, salt is left behind, making the remaining water saltier. This process is known as 'haline circulation.'

In contrast, most inland lakes do not have high salinity because they do not have a connection to the ocean, and their sources of water do not contain as many dissolved minerals. Lakes usually have fresh water, which contains very little salt. However, some lakes can be saline if they have no outlet or if their sources of water are high in dissolved minerals.