Why is sea water salty?

(Dan Tri) - Everyone knows that sea water is salty, but not everyone has the answer to why sea water is salty.

If you have ever been to the beach, you must have accidentally swallowed a mouthful of sea water and felt its intense saltiness. The reason sea water is salty is because it contains a very large amount of salt. According to scientists ' calculations, the oceans contain about 50 million trillion tons of dissolved salt.

Where does the salt in the oceans come from?

When it comes to salt, many people will simply think of a spice on the dining table. However, salt is more than just that.

In chemistry, salt is used to refer to any compound that has positive metal ions (Sodium, Potassium, Magnesium…) and negative acid ions. These salts are diverse and are found in many types of rocks around the world .

Ocean water contains a huge amount of salt, accumulated over millions of years (Photo: iStock).

Salt is not naturally present in seawater, it is slowly transported into the oceans from hills, rivers, etc. The continuous flow of water from rivers and streams causes erosion and weathering, causing minerals, including salt, inside the rocks to dissolve and be carried away by the water towards the sea.

In addition, there are many active volcanoes and hydrothermal vents at the bottom of the ocean, which are cracks in the Earth's surface where hot water and chemicals from the Earth's core erupt. These eruptions release many minerals, including positive and negative ions that form mineral salts.

Undersea volcanic eruptions also add salt to the ocean (Photo: NOAA).

Why is lake and river water not as salty as the sea?

Water in rivers and streams also contains salt molecules, but the amount is too small to create a salty taste like the sea (Photo: Pinterest).

The question is why is river and lake water, which also contains salt molecules from rock erosion, not as salty as sea water?

In fact, lake and river water also contain a certain amount of salt, but it is not significant, which does not create the characteristic salty taste like sea water. Only when salt flows into the oceans, the salt accumulates here after a long time, creating a salty taste.

Why doesn't sea water become fresh again?

Many people will ask why fresh water continuously flows into the sea from rivers, but this amount of water cannot dissolve and reduce the salinity of seawater?

According to scientists, the process of accumulating salt in the sea has been formed over millions of years, with salt continuously added from rivers.

Coastal waters with too much salt content will lead to precipitation (Photo: Getty).

As seawater evaporates into the atmosphere, it retains the salt molecules in the sea, increasing the salt concentration in the ocean. Meanwhile, new salt molecules continue to be carried by water from rivers and streams from the mainland, creating a continuous cycle of salt being brought into the oceans, making the seawater salty.

How important is the salt content of the ocean?

Seawater is salty, but the salinity of the sea varies from region to region. For example, in some shallow coastal areas, the concentration of salt can be so high that no more can dissolve, resulting in a layer of salt precipitate forming on the seafloor.

The salt concentration and salinity of seawater is responsible for many different weather phenomena on Earth.

The salinity of seawater will create ocean currents, greatly affecting many areas of science and life (Photo: Mozaweb).

Ocean currents, which circulate warm and cold ocean water around the planet, are considered important regulators of global climate. These currents are created by winds, temperature, and salinity of ocean water.

Just as meteorologists measure air temperature to predict what will happen in the atmosphere, oceanographers measure wind speeds, temperature, and salinity of ocean water to predict ocean currents.

Ocean currents affect the temperature and humidity of the atmosphere, so forecasts related to ocean currents play an important role in many fields of science and life, such as forecasting extreme weather events, exploiting maritime transport or forecasting fish movement directions for fishing...

Source: https://dantri.com.vn/khoa-hoc/vi-sao-nuoc-bien-lai-man-20250728150749578.htm