Why are lakes freshwater and oceans saltwater? (Smithsonian.com)
Why are lakes freshwater and oceans saltwater?
Lexile

It has something to do with this leaky faucet. You see, rain falls on the land as fresh water. As this water flows downward, it ever so slightly erodes the rocks and soil. This causes an ever so slight amount of salt and minerals to dissolve in the water and continue downstream. Eventually, all the dissolved minerals get dumped into the ocean.

Meanwhile water on the ocean's surface evaporates into the air, ditching all those salts and minerals. It then falls back on land as fresh water, replenishes the lakes and rivers, and the cycle continues. In lakes and rivers, theres enough turnover that the water stays fresh. But in the oceans, the salts pretty much stay there for millions of years.

Worldwide, it's estimated that rivers dump about 4 billion tons of salts into the oceans each year. But even with all that new salt, the oceans are so big, that their salinity stays fairly constant, at about 3.5%.

Critical thinking challenge: How is the water cycle like a bicycle?

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COMMENTS (102)
  • kalin0604
    6/02/2014 - 10:18 a.m.

    It has something to do with this leaky faucet. You see, rain falls on the land as fresh water. The rocks and minerals get in the water and somehow makes salt.

  • KiyanaF-2
    6/02/2014 - 07:49 p.m.

    Why are lakes freshwater, and oceans saltwater? Well it has to do with leaky faucets. Rain falls onto the land as fresh water but as the water moves downward it passes through rocks and minerals, it ever so slightly gains salt. This water is then poured into the ocean water. It's estimated that rivers dump about 4 billion tons of salts into the oceans each year. But with all that new salt, the oceans so big, that their salinity stays fairly constant, at about 3.5%.

  • Jason0421-YYCA
    6/02/2014 - 09:30 p.m.

    I think it is amazing that salt water that is from the ocean can be separated from fresh water, which then drops the fresh water onto a lake. I think that this process is amazing because it isn't easy to separate slat water from fresh water. I think that this process, can help people drink more water and also let other animals drink fresh water.
    Critical thinking challenge: How is the water cycle like a bicycle?
    Answer: The water cycle is like a by circle because the process goes around forever.

  • kaileyt-1
    6/03/2014 - 07:06 p.m.

    Lake water is called freshwater because Rain falls as fresh water and ocean water is called salt water because after the rain falls it goes down hill collecting minerals and salt and finally goes into the ocean causing "salt water" and when it rains this cycle happens all over again. This is a very interesting Article because I have never throughout about this and now that I saw the article it all makes sense.

  • kaileyt-1
    6/03/2014 - 07:06 p.m.

    Lake water is called freshwater because Rain falls as fresh water and ocean water is called salt water because after the rain falls it goes down hill collecting minerals and salt and finally goes into the ocean causing "salt water" and when it rains this cycle happens all over again. This is a very interesting Article because I have never throughout about this and now that I saw the article it all makes sense.

  • Eugene0808-YYCA
    6/03/2014 - 08:41 p.m.

    I learned this during science in this unit called Fresh Water. I don't actually know why lakes are fresh water, but i'll take a shot. Lakes are freshwater because the evaporated salt water goes up and gets turned into clouds. Then, the clouds release precipitation which is now freshwater. Then, the freshwater falls into a crevice and it eventually creates a lake.
    Critical Thinking Challenge: How is the water cycle like a bicycle?
    Answer: The water cycle is like a bicycle because the water cycle is constantly repeating like a treadmill.

  • BrianL-3
    6/03/2014 - 09:24 p.m.

    This article is about salt water in the ocean and why it is not in lakes and rivers. This is because when water evaporates it leaves salt and minerals behind. When it falls back down as rain it corrodes minerals and takes the dissolved minerals with them to the ocean. This process has happened over millions of years causing the oceans to have a salinity of about 3.5 percent. This is an interesting article because fresh and salt water provide many different things and resources.

  • danielarodrguez
    6/03/2014 - 10:58 p.m.

    Summary:
    This article is about how the ocean is salt water and the lakes and rivers are freshwater. The ocean is salty because dissolved minerals get dumped into the ocean. Rocks and soil erodes and turns into salt. When the water evaporates, it comes back down as fresh water, and then the cycle continue constantly. Even though, that new salt do not increases the oceans' salinity, because the oceans are enormous.

    Opinion:
    From my view point, this article is very interesting because I've always wondered why an ocean has salty water. It's very interesting for me to know about this topic, because I think that everyone has ever wondered about it.

  • camilla5k24
    6/03/2014 - 11:29 p.m.

    The water cycle is like a bicycle because they have the. Word cycle in their name and they both start at one point and keep going. They both make a circle. And help us keep alive and active.

  • jacquelineh-5
    6/03/2014 - 11:57 p.m.

    This article is about why the oceans are saltwater and why lakes or rivers are freshwater. As it rans onto mountainsides, and then that water flows down a river or stream, the water picks up different minerals, including salt. Once the river or stream is connected to the ocean, all of that salt is brought along with the added water. The process continues when ocean water is evaporated into the air, but leaves the salt behind. It then rains again, and the process restarts. I found this article very interesting, and I learned a lot of information from reading it.

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