why is the ocean salty, and how did it get that way?
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Over millions of years water dissolved salts out of the ground. Rivers carried that water into the sea where the plain water evaporated leaving salts behind. More salt was brought into the ocean but it could never leave and increased in concentration.
Salt exists and can dissolve in water. When water evaporates from the ocean it doesn’t take salt with it, and falls on the land as fresh water. That water runs over the land and encounters salt in landscape. That salt will dissolve in the water as it runs downhill, eventually reaching the ocean.
Literally rinse and repeat and this results in salt making its way into the ocean over time.
The other two answered correctly. Also, it’s in equilibrium now so it won’t get saltier. Per google “the proportion and amounts of dissolved salts per unit volume of ocean are nearly constant and have been so for millions of years. So, no, the ocean is not getting saltier and this is because the processes that add and remove ions are in balance.”
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This is a vintage undergraduate geology question, good one!
You have half the answer already from others. The components of table salt (sodium, chlorine) are in some rocks, and will dissolve. So over time they wash into the sea from rivers.
But the next half of the question is: loads of stuff in rocks will dissolve. A lot of it dissolves more readily than sodium and chlorine (e.g., calcium, phosphorus). So why is the sea table-salt-y specifically? *This* is because the other compounds are much more useful to critters and/or easy to incorporate into new rocks. So, most other things that are washed into the sea get taken out again pretty fast. Sodium and chlorine are much less (though not completely un-)useful, so they are the ones that build up to levels we can taste.
This is a classic “mass balance” question, where you have to think about what comes out as well as what goes in to get the full answer.
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Rain washes salt from the land into the sea, then the seawater evaporates forming clouds and more rain but leaves the salt. More rain falls, washing more salt into the sea and the cycle continues. Vey small amounts of salt build-up over millions of years to make the sea now about 3.5% saline by weight.
Over a million years salt collected in the water as a run off from the land where salty people cried and complained all the time during the ice age because it was too damn cold.
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