Why is the ocean salty but river is not? Where does all that in ocean salt come from?

Published on 12 March 2021 08:04 AM

Have you ever wondered why ocean water is so salty? Where does all that salt come from? If seawater is so salty, why is the river not salty at all? Are some places saltier than others, if so, why? Oceans are huge. They contain 1.3 billion cubic kilometers of water. To make such a waterbody salty, imagine the amount of salt that would be needed.

On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every kilogram which is roughly one liter by volume of seawater has approximately 35 grams of dissolved salts.

If all this salt could be taken out of the ocean and spread over Earth’s land surface, it would form a layer more than 150 meters thick.

You may ask if seawater is so salty, how do sea animals still survive in it? We will answer all these questions in a bit. You just need to sit back, relax and subscribe to our channel for more such answers to amazing questions. Salt, a mineral that is essential to all life forms in general. Some of the earliest evidence of salt processing dates to around 6,000 BC, when people living in the area of present-day Romania boiled spring water to extract salts; a salt-works in China dates to approximately the same period. Salt was also prized by the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites, Egyptians, and the Indians. Saltiness is one of the basic human tastes. Salt was discovered by early humans(Neanderthal). When the human discovered fire, they learned the art of cooking and eating and started adding flavor to their food. One such day when they gathered around to fire up and cook their hunt, they wanted to was the flesh of the animal first. As there was a salty sea/ocean nearby, a member went to wash their hunt. When the food was finally cooked, it tasted so good and they discovered that washing food in the ocean can make it taste good. so they started washing all their food in the sea. Later on, a wise man among them found what exactly was there in the sea for the food to taste salty, and hence salt was discovered.

Over millions of years, the concentration of salts has increased from possibly almost fresh in the primeval sea to where it is now.

Saltiness differs from place to place in the ocean depending upon its distance from the equator, inflow of fresh water from the river, and ocean currents.

Deep in the ocean, under high pressure, seawater can reach a density of 1050 kg/m3 or higher.

The saltiness in enclosed seas, such as the Mediterranean and Red Seas, can be very high due to less rainfall and difficult access to water from the deep sea.

Some of the salt in the sea comes from undersea volcanoes and hydrothermal vents, but most of it comes from the land.

Salt in Ocean has ancient origins, when the earth formed, salt entered along with other minerals and dissolved in water. Salt cannot be evaporated, so the salt has nowhere else to leave, hence it has been adding continuously to the oceans since forever.

Not only this, water in rivers that flows into the sea brings along the dissolved salt contained in rocks. Rivers carry almost 4 billion tonnes of salt to the sea each year.

This entry of salt into the ocean is a 1-way street because there is nowhere else for salt to go. Oceans have been collecting salt from such runaway water bodies since ancient times.

In lakes and rivers, the relatively rapid turnover of water and its dissolved salts keeps the water fresh – a water droplet and its ions will stay in Lake Superior for about 200 years, compared to roughly 100 to 200 million years in the ocean. Even if you did have any accumulation of an ion in a lake, it would be washed out quickly. The constant replenishing of rivers with rainwater keeps rivers from becoming overly salty - as the salt is always pushed out and into the seas, where it collects.

Drinking enough fresh water will help dilute the salt in our bodies. And depending on what and how much we eat and drink, our kidneys will remove excess salt and put it in our urine so we can get rid of it. So how would fish or sea creatures survive in such salty water?

Some sea animals, such as ghost shrimps, can take in large amounts of salt and will maintain a balance similar to the water around them.

They have developed ways to manage the amount of salt in their bodies and are known as “osmoregulation”.

Fish can drink salt water and eliminate the salt through their gills.

But different fish have different limits. Some saltwater species, if they are trapped in more salty water, will die.

These animals change their metabolism to survive in different water conditions. Crocodiles living in saltwater have adapted by developing special glands in their tongues to help them excrete salt.

Salmon spend a relatively short time in freshwater before developing the capacity to osmoregulate in seawater, where they live for the majority of their lives.

Seabirds and turtles also need to remove salt from their bodies, but they have what we call “glands” to help.

And seabirds and turtles also have kidneys that remove salt in the same way that fish do.

So, the reason marine animals don’t get sick when they drink seawater is that the species have lived in marine water for a very long time and are adapted to living in that environment.

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