A. Why is the sea salty?Well, on average, seawater is made up of around 3.5% salt
and other minerals (so the oceans are 96.5% water, 3.5% salt). Most of this is the
ordinary table salt (sodium chloride) we use every day. So where does it all come
It is believed that minerals from within the Earth seeped into the seas through vents
in the ocean floor (through the crust of the Earth in effect) when the oceans were
first formed. Today, rivers and streams continually carry salt and other minerals
to the ocean as land rocks get gradually eroded by water and the weather. When water
evaporates from the sea (to fall again later as rain) the salt within the water is
left behind where it concentrates. In addition, winds also carry particles which
get deposited into the water and decomposed organisms also add some salinity.
The amount of salt in our seas has remained pretty consistent for a long time now,
despite the ongoing flow of minerals from rivers etc. This is because some of the
salt gets removed when it hits the sea bed (one theory is that it moves or gets forced
back under our land masses).
So why aren’t our rivers salty? Well, river water and streams can contain a small
amount of salt but because there’s only a trace, we can’t really taste it. Rivers/streams
are rushing or moving waters so salts don’t tend to accumulate or concentrate.