Question

from where did tons of salt came from in ocean

Answer 1

Salt in the ocean comes from rocks on land.The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid (which forms from carbon dioxide and water).Two of the most prevalant ions in seawater are chloride and sodium. Together, they make up over 90 percent of all dissolved ions in the ocean. Sodium and Chloride are 'salty.'

Answer 2

This may seem surprising, but the salt from the ocean comes from the "fresh" water in the rivers. In fact "fresh" water is not totally fresh (there is even a little bit of salt in your tap water!). The amount of salt in the rivers is very low, but when that river water dumps into the ocean the water evaporates and turns to clouds and rain, but the salt stays in the water. In this way, over hundreds of millions of years the ocean has been gradually becoming more salty.