ocean and salt

[Fleisc]

What happens once salt gets into the ocean?

[gen2]

The simple answer is nothing.  Over millions of years the oceans have got saltier and saltier.  There are in fact three ways in which some salt can leave the oceans.

1. Under high wind conditions, salt spray can get blown in land.  Natural drainage and leaching means that most of this will very soon return to the oceans.

2. In subduction zones, seabed sediments containing salt are drawn under the earth's crust into the mantle.  Some may then later re-emerge during volcanic activity.

3. In the geological history of the earth, there have been several occasions where (either because of falling sea levels or rising land masses) a section of ocean has been cut off from the rest of the oceans.  If the climatic conditions have led to the rate of evaporation being graeater than the inflow of fresh water, then the cut-off section of water dries up leaving behind all dissolved solids.  These are known as evaporite deposits.  Salt is mined under Cheshire from just such deposits.