十万个为什么·科学启蒙30篇（1）

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为什么海水是咸的？

Rainwater flows over rocks and dissolves tiny amounts of salt minerals along the way.
Rivers carry this dissolved salt into oceans over millions of years.
Volcanic activity under the sea also adds minerals like sodium and chloride.
Ocean water does not get saltier forever because some salt sticks to clay or forms sediment.
Evaporation removes fresh water but leaves salt behind, making surface water denser.
Salt concentration varies: the Dead Sea is much saltier than the Atlantic Ocean.
Marine life depends on stable salt levels to control water balance in their bodies.
Scientists measure salinity using special sensors on research ships and buoys.
Melting glaciers add fresh water, which can temporarily lower local ocean salinity.
Understanding salt movement helps predict ocean currents and climate patterns.