You have many interesting questions, which really make me think. There are various sources of salt in the sea. When it rains, the rain water collects all kinds of minerals, those in atmosphere, on rocks, on soil.These are eventually deposited in the sea and form the sea salt. Also volcanoes that happen in the sea add salt – due to the minerals that are released from earth’s crust during volcanic activity. In some sea bases, there are also active vents which release water and minerals from sea crust (the core ) to the sea. All these processes, which have been happening over many millions of years, contributed to the salt in the sea.
@Kings Interesting question.. I have never really thought about this, which is bad, because I come from the coast bordering the Indian Ocean which is too salty, urgh! But, from my geography lessons, I learnt that salt in the sea actually comes from the land. Rain water corrodes minerals (and ions) from rocks and other natural structures on land. We know that all this water collects into streams and rivers.. which eventually drain into the sea/ ocean. While other components of the minerals are “used up” by sea plants and animals, sodium and chloride are not used equally fast. These two ions then combine chemically to form “sodium chloride”.. hence the salty sea! My interesting self reflection would be: why are some oceans more salty than others, or why are some not salty at all?? Think of the Dead Sea where you can actually float without effort (good for me because I can’t actually swim hihi)