The Ocean's Composition
96.5% of Earth's ocean water is water, and 3.5% is dissolved minerals. Earth's saltwater mainly has the minerals sodium and chloride in them, which makes them salty.The minerals that make up Earth's oceans come from rivers and streams that dump sediment and dissolved minerals into the Earth's oceans. Earth's water is denser on the top than it is on the bottom because the sunlight can reach through the shallower waters. This make water evaporate leaving the dense salts behind. Towards the bottom, though, The sunlight isn't able to penetrate, and so less water is able to evaporate.