Interactive Explainer
Why is the ocean salty?
Ocean salt mostly comes from rocks on land and from chemical exchanges at the seafloor. Rivers and groundwater carry dissolved ions into the sea, while evaporation removes water and leaves those salts behind.
Water leaves the ocean far more easily than dissolved salts do, so salts accumulate over long timescales.
Rivers do bring dissolved minerals to the ocean, but they are usually diluted enough that we do not taste them as salty.
Hot, dry basins usually get saltier, while estuaries and rainy regions are often fresher because more fresh water is mixing in.
Try It Yourself
Salinity Lab
Increase evaporation, pour in river minerals, freshen the surface with rain and runoff, or strengthen seafloor chemistry to see how a basin drifts toward briny or dilute water.
What changes the fastest
What is driving the result
The Big Idea
What is actually happening?
An interactive explainer about where ocean salt comes from, why rivers are not usually salty, and why some seas are much saltier than others.
Rocks weather on land
Rain and chemical weathering break minerals from rocks. Rivers, groundwater, and runoff carry dissolved ions toward the sea.
The ocean stores dissolved salts
Once ions like sodium and chloride enter the ocean, they can remain there for very long times because the sea is such a large reservoir.
Evaporation removes water, not salt
When ocean water evaporates, the water molecules leave but most dissolved salts remain behind. That concentrates the seawater that is left.
Chemistry still removes some ions
Salinity is not a one-way ratchet forever. Shell formation, mineral precipitation, and seafloor reactions remove some ions too.
Good Follow-Up Questions
The details are where this gets interesting
The short answer helps, but the edge cases and comparisons are what make the topic memorable.
Rivers are not usually salty to our taste
They carry dissolved minerals, but the concentration is usually far lower than in seawater because river water is constantly refreshed and diluted.
Some enclosed seas get very salty
In hot, dry basins with strong evaporation and limited outflow, salinity can climb well above the open-ocean average.
Rain is fresh because salt does not evaporate with it
Evaporation lifts water molecules into the air, not most dissolved ions. That is why rain can refill the system without being ocean-salty itself.
Compare Scenes
Why the same ocean chemistry does not look the same everywhere
Salinity depends on the balance between incoming minerals, evaporative concentration, fresh-water mixing, and local circulation.
Fast Answers
Questions people usually ask next
Good science pages should answer the obvious follow-ups without making the reader hunt for them.