So, how do we remove salts from the ocean?
Well, it was originally thought that this would have been done by evaporites.
And this is where the seas start to shallow, the salinity increases,
and then evaporation would, would simply just leave these salt deposits,
such as gypsum and anhydrite and
the more familiar sodium chloride, which appears as the mineral halite.
Now, this has been common at certain times in the geologic record, but
it's never been sufficiently abundant to account for
all the salt removal that you would need over geologic time.
And for that, I want to go to this example here.
Here, this is the Mediterranean Sea, and you can see it's a relatively
enclosed basin fed by the rivers around the Mediterranean, and
then just this small gap right here between the Straits of
Gibraltar connecting the Mediterranean Sea to the Atlantic Ocean.
Now, about 5.5 million years ago, the Strait of Gibraltar
was closed due to changes in sea level and changes in sedimentation.
And we see abundant gypsum and
other evaporite deposits around the Mediterranean.
This one here being from Tunisia on the south coast of
the Mediterranean in Africa.
So, here we are about this period around 5 and
a half million years ago, where the Straits of Gibraltar have closed up,.
And essentially, what's been left has just been this