Why is the Sea Salty? | Earth Unplugged

hi I'm Maddy have you ever considered

why the sea is salty on average our

oceans consist of about 3.5 percent salt

that equates to a total of 50 million

billion tons of salt in our seas it'll

take a pinch if you were to pile all of

that salt onto the Earth's land it would

create a layer 152 metres high so how

did it get there

well some salts dissolved into the ocean

from rock and sediment on the sea floor

other salts escaped from volcanic vents

did beneath the waves but most of it

comes from the land around us rain water

dissolves minerals and salts from the

rocks on dry land

so as rainwater makes its way down river

it collects more and more salts the

amount of salt in this fresh water is

still tiny about 220 times less than

seawater but it is there and this salt

is then deposited into the sea when the

river has run its course

importantly the salt then becomes more

concentrated in the sea because the

sun's heat distills the water from the

ocean surface leaving the salt client

across the globe 4 billion tons of salt

are deposited into our oceans every year

from rivers so surely our seas must be

getting saltier certainly the oceans

have got a lot saltier since their

primeval beginnings but now just as much

salt is being deposited on the ocean

floor as he is coming from the rivers so

it's reached a general equilibrium

however there are differences in

salinity across the globe towards the

poles seawater is diluted by melting ice

caps and heavy precipitation meanwhile

in areas bordering the equator where

it's hot evaporation rates exceed the

amount of rainfall so water here is much

and there is evidence to suggest that

these differences are increasing as sea

temperatures rise parts of the Atlantic

have already shown great evaporation

rates and with it a rise in salinity

levels this may not seem important but

the more salt in the ocean the greater

its density and the slower it will

circulate meaning that important marine

nutrients won't get distributed around

the globe but interestingly it's not

just your everyday sodium chloride that

is gathered by rainfall and freshwater

systems rivers actually carry and

deposit more calcium than chloride so

why is it our seas aren't full of

calcium it's because living organisms

like mollusks crustaceans and coral use

huge amounts of calcium as various forms

to build their body structure without

this influx of salt and minerals from

our rivers and streams life would

certainly be very different in our

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bye what about a hurricane how much

water is in one of those well they are

huge of have a much higher water density

so much so that their average water

content has been estimated at 50

thousand metric tons we think of our

planet as a watery place the blue planet

70% of the earth's surface is covered in

water and in fact water's unique as the

only natural compound that occurs in all

three states but if we scooped it all up

and sculpted that water into a sphere

how big would that sphere thing