Worldschooling

In this blog post, I’m going to be writing about a question that has pondered me many times. My question is, why is there salt in the ocean? And, more specifically, why is there salt in the ocean, but not in freshwater? I decided to write this post because I really have been wanting to know the answer to this question, and I thought this would be a good time to do that since we’re in Croatia and there’s plenty of opportunities to go to the beach and swim in salt water.

When you were little, your parents probably told you that there was salt in the ocean and you might not have stopped to think why, because you knew your parents were right. Or, you found out on your own by coughing up a mouth full of it by accident. But whatever way you learned about salt in some water, and no salt in other water, you’ve probably asked yourself how salt got into water in the first place. Today I’m going to be giving you the answers to all those questions. But before you continue reading, I will challenge you to think of an answer to them if you don’t know the answers already.

The process of how salt gets into water is pretty complicated and I’ll try to explain it the best I can, but if you get confused, you can read it over again or do more research. I Feel free to read as slowly as you want so that you can process everything. So without further ado, this is how salt converts it’s way into water.

A long time ago, there probably wasn’t as much salt in the ocean as there is now. The reason for that is because salt moved into the ocean through minerals in rocks… So that means that the salt in the ocean mostly comes from rocks on land. But not just any rocks. Specifically rocks on land. Why on land?

Well technically it all starts with rain. Rain contains dissolved carbon dioxide from the air around it. When carbon dioxide and water mix, this creates carbonic acid, making the rain water acidic. When it rains, the rain water falls onto rocks ON LAND. Again, why rocks on land? Since rain can’t fall on rocks through the water, the obvious explanation is that salt can only come from rocks, or minerals, on land.

Continuing on, when rain water falls onto rocks, this causes erosion, and the acids in the rain break the rock down. All this creates ions to form. Ions are micro sized particles that have electricity inside of them. So in other words, they are “electrically charged”.

These ions get carried with streams from rivers and eventually land in the ocean, where most are used by tiny creatures, or organisms living in the ocean. The ions that are used by organisms end up being removed from the ocean. But the lucky ions continue to be part of the process of creating salt water. These ions that are not used, are left on their own for such a long time that other ions continue joining the group until there is a whole concentration of ions in one area.

The two biggest groups of ions are Sodium and Chloride, which are presumably “salty”. On an average, there are 35 parts of salt in ocean water every thousand concentrations. This means that 3.5 percent of the weight of ocean water is salt. Another fact about how much salt there is in the ocean is, according to some estimates, if you took all of the salt out of the ocean and layered it on top of the perimeter of the earth, it would be even thicker than 500 feet, or, in height, about a 40 storied office building. That’s as tall as a skyscraper that you could find downtown.

Okay, now that we’ve got salt water covered, there’s one more question that I’m going to answer today. Why is there salt water in the ocean, but not in rivers or lakes? Well, it turns out the answer is simple.

Do you remember when I told you that the ocean started off not being very salty? And it got saltier through the minerals in rocks? Well, how do you think those minerals traveled to the ocean? Through rivers and streams that left from lakes of course. The lakes and rivers themselves got filled back up with fresh rain water, and the minerals in the lakes and rivers escaped through streams running back into the ocean. So, the cycle continues to stay like this. The minerals end up in the ocean through streams, making the ocean salty, and the rain fills the lakes back up with freshwater. Every year, rivers around the world convert approximately 4 billion tons of dissolved salts from rocks into the ocean.

So now we’ve covered salt water and fresh water. You would think we were done right? Wrong. There’s still one thing that doesn’t quite make sense. See, if the streams that run into the ocean carry salt, well if you want to be exact 4 billion tons of dissolved salts every year, then wouldn’t the ocean just get saltier? And even saltier? You would think. But again, no.

Here’s why; Every year, around the same amount of salt that runs into the ocean (4 billion tons), is most likely deposited on the ocean floor as sediment. So all in all, there’s about an even amount of salt that makes it into the ocean and stays there, and an even amount of salt in the ocean that ends up becoming waste. Which means that the ocean gains and loses around the same amount of salt, and the ocean doesn’t get any saltier than it already is.

As it turns out, the salt water cycle (or process) can get pretty complicated. Today we covered the main topic of why salt is in the water, then we took on why there is no salt in rivers or lakes, and finally we ended with a question that came up during the salt water topic; if freshwater streams carry x amount of salt to the ocean annually, then wouldn’t the ocean get saltier? I hope you found your answers to these questions. If you want to learn more about these questions, or the salt water topic in general, you can always research more about it, and if you want to know where I got all this information, you can check out the links to these sources down below.

I don’t know about you, but I think learning about the cycle of salt water is very interesting and I would like to continue learning more about it. It was very fun uncovering this salt water mystery and I hope it was for you too. My next blog post is going to be about my experience learning how to sail with Jack in Croatia, so make sure to stay tuned for that.

Bye for now, Lily🍦

https://oceanservice.noaa.gov/facts/whysalty.html
https://oceanservice.noaa.gov/facts/riversnotsalty.html