What happens to salt water and fresh water when you try to mix them.

the lighter fresh water rises up and over the salt water

Explanation:

this is because the salt water is denser

When trying to mix fresh/salt water it leads to variable and dynamic chemical conditions, especially salinity because fresh water flowing into the estuary is less salty and less dense than water from the ocean, it often floats on top of the heavier seawater.

Explanation:

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the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).