Seawater Facts & FAQ ~ Sea Water

by Teresa Smith

in Ocean

Seawater is simply the water  from the sea. Since it is salty, it is also called saltwater. Seawater makes up 70% of the earth’s surface area and .02% of its total mass. In relation to the rest of the earth, it is really just a thin film over a rock comparable to wrapping a tennis ball with a paper towel and then cutting out some for land masses.

Seawater Facts


Here are some seawater facts and FAQ:

Is it sea water, sea-water or seawater?
All 3 are used. Only seawater is in the dictionary.

Is seawater a compound?
No, it is a mixture.

What percentage of the earth’s water is seawater?

Why is the ocean salty?
Dissolved salts from land and from inside the earth make their way into the ocean where they stay.

Where does the salt in the ocean come from?
Water is a powerful solvent and can dissolve most anything it comes in contact with, albeit slowly. So when comes in contact with these salts, it dissolves some of it which finds it way into the ocean.

The entire volume of seawater makes it’s way through the earth once every 6-8 million years. During this process, chemicals that make up salts are dissolved and end up in the ocean. Salts don’t evaporate so they stay in the ocean and concentrate to the the point where, currently, the average salt content of seawater is 35 parts per thousand.

What are the dissolved salts in seawater?
There are many salts in the ocean but common table salt (sodium chloride) is the is the most prevalent. There are also salts made from sulphur, magnesium, calcium and potassium.

Can seawater burn? 
Not really. Water is made up of flammable hydrogen and oxygen. Splitting them apart in a process called hydrolysis or even radio waves 1 can yield their individual elements. Combined, though, they will not burn.

What is the composition of seawater?
Seawater is 96% water. The other 4% includes:

  • Ions: chloride, sodium, sulfate, magnesium, calcium, potassium, and bicarbonate.
  • Elements: 80 elements have been detected in seawater with some in concentrations as low as 1 part per trillion.
  • Dissolved gases: nitrogen, oxygen, and carbon dioxide

What is the density of seawater?
The average density 1.025, which is slightly above pure water’s density of 1.0. This is due to the dissolved salts present in all seawater.

What is the salinity of seawater?
The concentration of salts (salinity) in seawater averages 35 parts per thousand which is about 1/2 cup of salt to every gallon of water.

Is the salinity of seawater constant throughout the oceans?
No. Seawater near freshwater deposits like rivers and glaciers have a lower salinity. Deep, cold water has a higher salinity. The Pacific Ocean is saltier than the Atlantic Ocean because it is larger and less affected by river runoffs.

What is the specific gravity of seawater?
Averages 1.028 at 77oF.

Will the ocean continue to get saltier over time?
Not really. It’s reached somewhat of an equilibrium.

  • Salinity increases with runoffs, erosion and from water circulating inside the earth.
  • Salinity decreases as salts are deposited on the seafloor as sediment, which can get pushed deep into the earth through shifting plate tectonics. Salts are also bound up in animals such as clams (their shells) and then deposited as sediment on the seafloor.
    Salts are also deposited on land via wave tip sprays that form salt dust that is carried by the wind.

Can humans drink seawater?
Not for long. There is a half cup of salts in every gallon of seawater that you body needs to get rid of. Our kidneys are need to dilute the seawater with freshwater to be able to excrete it in urine. Thus the body grabs water from elsewhere in the body until there is no more left and then the kidneys shut down and you die.

Can some animals drink seawater?
Yes. They have the ability to excrete the excess salt. Marine iguanas, for example, have salt glands located between their eyes and nostrils which collects the excess salt. The iguana then sneezes out the salt which can land on its head forming a salt wig. Most ocean dwelling animals obtain all of their water from the food they eat and only rarely drink water.

Marine Iguana with Salt Wig

Marine Iguana with Salt Wig credit:

What is the speed of sound in seawater?
1,500 m/s.

Why does sound travel faster in seawater than freshwater?
Pressure, temperature and salinity affect the speed of sound greatly.

How does oxygen get into sea water?

  • Wave action and aeration dissolves atmospheric oxygen
  • Plants like algae release oxygen
  • River and storm runoffs

How much dissolved oxygen do animals need?

Dissolved oxygen needs of various ocean animals

Dissolved oxygen needs of various ocean animals expressed in mg/L.

How are the salts removed from seawater in a desalinization plant?
Reverse osmosis filters.

What is the average temperature of the ocean?
The mean temperature of the ocean surface waters is 62.6oF.

The most abundant salt in seawater is?
Table salt. NaCl.

How to make sea water?
add 1/2 cup of table salt (no iodine) to 1 gallon of water.

Is there gold dissolved in seawater?
Yes. 20 million tons of it. But it is so diluted, that filtering it out is impractical. 2

Is there uranium in seawater?
Yes but at 3 parts per billion, it is very diluted.

Can the uranium in seawater be mined?
Yes. It is expensive but always available if land reserves become depleted.

Do seagulls drink sea water?
Yes, but they prefer fresh water.

What would happen if all of the salt was removed from Earth’s Oceans?
Marine life would die as they are not adapted to freshwater. Seawater, being less dense, would evaporate quicker causing more storms.

Are there seawater based nasal sprays?
Yes, a Google search will show them.

Know any additional seawater facts? Leave them in the comments below for others to read.

facts about sea water-sea water facts-SEAWATER-

Leave a Comment

Previous post:

Next post: