Every time you go to the sea, you accidentally swallow seawater! Have you ever wondered where this vast saltiness comes from? Let's uncover nature's secret about the journey of saltiness from mountains to the ocean, along with why rivers are not salty, explained simply.
When visiting the sea and jumping into waves, many people have accidentally swallowed seawater and been overwhelmed by its saltiness. This often raises the popular question in their minds. "Why is seawater salty?" Did someone pour salt into the sea, or has it been salty since the age of dinosaurs?
Today, we'll reveal nature's secret in an easy-to-understand way. After reading this, your next trip to the sea will change how you see seawater.
In reality, seawater's saltiness isn't magic but results from natural processes accumulating over billions of years, mainly from two sources.
The origin of saltiness isn't in the sea but on land! When rain falls, it combines with carbon dioxide in the air to form weak acid. This acid slowly erodes rocks and mountains, extracting "minerals" hidden inside—especially sodium and chloride, the components of salt.
These minerals then flow with water into streams and rivers, eventually reaching the "ocean." Imagine rivers worldwide as conveyor belts transporting salt to the sea daily over millions of years; it's no wonder the sea is salty.
Besides minerals from land, deep under the ocean are cracks and volcanic vents that release hot water. Seawater seeping beneath the Earth's crust dissolves minerals underground and spews them back into the ocean, adding saltiness from the ocean depths.
If rivers carry minerals to the sea, why don't we taste saltiness in river water?
The simple answer is Rivers are like transit routes. River water constantly flows with fresh water from rain and upstream sources, so the mineral concentration is very low—too dilute for our tongues to detect saltiness.
The ocean, however, is the final destination. Water flowing into the sea has nowhere else to go except to evaporate into vapor and form clouds. Sunlight evaporates only pure water, leaving minerals behind to accumulate, increasing seawater's saltiness over time.
| Scientific data shows that on average, seawater has about 3.5% salt content. To visualize, if you evaporate one kilogram of seawater, you'd get approximately 35 grams of salt. |
Seawater's saltiness is nature's masterpiece created over a long time—from rain washing over mountain rocks, flowing through rivers, and finally accumulating in oceans—a never-ending water cycle. Now that you know, your next sea trip will come with a cool fact to share with friends or kids.