Why is the sea blue?

Discussion in 'Earth Science' started by lizi_88, Nov 8, 2003.

  1. lizi_88 Registered Member

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    Hey my lil bruva needs too no why the sea is Blue? does anyone know this? it would be much apreciated if you do. write back Lizi X

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  3. curioucity Unbelievable and odd Registered Senior Member

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    Hi and welcome to sciforums.

    About your question, blue sea can often be described as clear, that is, not too much things inside so that it can reflect the sky-blue color. Okay, first thing you may notice when comparing the two blues is that the sea-blue is darker.... it is because water can never be a perfect reflector, that is, while lots of blue lights are reflected to you, another great amount of blue lights goes deep inot the sea.

    Hope that answers some bits of your (and you brother's) curiosity.
     
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  5. lizi_88 Registered Member

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    Hi thank you it did help.
     
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  7. curioucity Unbelievable and odd Registered Senior Member

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    You're welcome.
    And by the way, I mentioned that clear sea is blue. If you're good at geography, you know some seas on earth are named based on their color: Black Sea in Mediterania and Red Sea between Asia and Africa being the most famous-> according to many, they are indeed of those colors, primarily because they contain algae which are black (for Black Sea) or Red (for Red Sea).
    Also, algae are the primary factors on why some parts of the sea are not blue; algae tend to stay close enough to the surface of the sea so that they reflect a lot of colors other than blue.
    Extra info to keep you happy.
     
  8. gMan Registered Member

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  9. Edufer Tired warrior Registered Senior Member

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    The color of seas, lakes, rivers and other water covered surfaces depend on many factors. One of them is depth of the body of water, another is the observation angle (the reflection and refraction laws in optics work here, scattering of light rays by particles, etc), another is the particulate content of the water (size and color), and other factors.

    As an example: the Amazon river has a light brown color, as most rivers that are born in high mountains do, because they drag along abundant clay particles that reflects the light to give the characterisic color. South of the city of Manaus, Brazil, it is joined by the Rio Negro (the Black River) that is <b>really black</b> as india or China ink. You can see, even from a boat close to the junction, both rivers going parallel for miles until finally the brown color takes over.

    The reason of the black color in the Rio Negro waters actually is he high content of organic material in suspension. The Rio Negro basin has no mountains, and the waters forming the river comes from the heavy rains in the jungle. The water falls from the leaves and flows down the Amazonian slopes to form creeks, bigger and bigger until they become a huge river as the Negro.

    But if you submerge a glass into those waters, it comes out full of --- clear water. You cannot see any impurities there (as you see when filling a glass from the Amazon river, that looks as a brownish lemmonade).

    Moreover, when one walks into the river, and stands with the water at knee height, you can see how the color of your skin starts to get reddish and darker as depth increases, and you can hardly distinguish your feet. The same happens with the really white sands in the shores of the Rio Negro: near Manaus they are white as salt, but as you walk into the river, the riverbed becomes redder and darker, until you believe the bottom is pure black. (I have travleed the Amazon and Rio Negro for years).

    The reddish color is due to the high content of organic matter (coming from the rotten leaves and plant debris in the jungle). Because of this, the decomposing organic matter absorbs oxygen and releases hydrogen ions, giving the river a high acidity (very low pH). The lack of oxygen and the low pH prevent the mosquito larvae from breeding, so there are no mosquitoes along the Rio negro riverbeds. No mosquitoes, no malaria, no yellow fever, no West Nile Virus, etc. The houses in Manaus are famous for not having mosquito nets in their windows.

    The acidity and lack of mosquito larvae also result in a very low fish population in the Negro. One thing takes to another. Nice, don't you think so?
     
  10. curioucity Unbelievable and odd Registered Senior Member

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    Wow, great info! But that means the people living near the river would have water problems, don't you think so?
     
  11. Edufer Tired warrior Registered Senior Member

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    Not at all. On the contrary, black waters in the Amazon are known to be free from bacteria and parasites, so it is the best water you can drink. I have traveled extensively the Amazon jungle for years, and in my trips by the rivers we usually went into the small black rivers for loading our water canisters for cooking and drinking.

    The brown waters are full of parasites (amoebas) that will give you lots of trouble. if you can read Spanish go to:

    http://mitosyfraudes.8k.com/Expe.html

    and read about some expeditions I did into the jungle. At least, you can see the pictures. Follow the internal links and see it all. And if you like indians, in the same site you can see indians from the Xingu National park. The site has an English version, but it is devoted to scientific ecology (also global warming" and ozone hole hoaxes). it is at:

    http://mitosyfraudes.8k.com/ENGLISH.html

    I guess you'll enjoy a visit there.

    Regards.
     
  12. curioucity Unbelievable and odd Registered Senior Member

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    surprising black water...... I thought that the acidity might cause big deals... so it's not? Oh, since you mentioned about optical factor, are the rivers you mentioned black from any angle?
    By the way.... if a body of water is deep enough, do colored matters have to be placed close enough to the surface so that they can be seen? If so, I wonder how shallow the Red Sea is, otherwise, Suez works.....
     
  13. Edufer Tired warrior Registered Senior Member

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    It all depends on the transparency of the water. The more loaded with particles in suspension, the less clear water is, hence objects must be near the surface for its image pass through to the outside.

    Take the case of famous clear waters in the world: the Caribeean waters are so clear that you can see all the objects in the bottom of the sea down to several tens of meters deep. of course, the angle of observation must be near the perpendicular to the surface, otherwise, refraction will prevent te light rays from reaching your eyes.

    On the other hand, on normal lakes, full of organic matter transported by inflowing rivers and creeks, as well the runoff from nearby hills, scatter the light to all directions and makes the waters lokk darker.

    i haven't been on the Red Sea, so i don'y know how it looks, if it really looks red at all, or if the name just comes from periodic upwelling of algae or other organisms (as the frequent "red tides" in the coast of nothern Patagonia, poisonous algae that contaminate shellfish making them no edible.

    have you visited the website I recommended?
     
  14. curioucity Unbelievable and odd Registered Senior Member

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    Yes, and as you have warned, the English site is too full of articles, while I can't understand Spanish...... eh, but I haven't explored deep enough....
     
  15. Edufer Tired warrior Registered Senior Member

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    Just take your time and go easy on it. You`ll find lots of info you never dreamed it existed.

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    In here is 3:20 am. What are you doing awake so late this time of the night?

    I am going now to bed. Cheers!
     
  16. curioucity Unbelievable and odd Registered Senior Member

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    bet we're in the opposites of the earth. I posted that during midday.
     
  17. Edufer Tired warrior Registered Senior Member

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    I'll bet my boots you are in Australia (or about there). I have good friends in Tasmania.

    I live in Argentina.
     
  18. curioucity Unbelievable and odd Registered Senior Member

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    Not too far if I may say.
    I'm in
    *spoilers for sticky threads in sciforums cath*




    Singapore
     
  19. Nasor Valued Senior Member

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    This is completely wrong. Water looks blue because water absorbs red light more strongly than blue light, so any light that passes through a sufficient amount of water will tend to look blue because some of the red has been removed. This is a result of the chemical properties of water, and has nothing to do with the color of the sky. You can look at a white light bulb through a large container of perfectly pure water and it will still look blue.
     
  20. curioucity Unbelievable and odd Registered Senior Member

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    Oh, well, okay, I take your correction. Maybe I missed the fact that the sea is blue when seen from <i>the inside</i>.
     
  21. John Connellan Valued Senior Member

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    Not really since u could argue that the sea is blue from the inside because u are generally looking at the sky!! Any other direction and the sea is dark grey or black. Ha ha, sorry!
     
  22. curioucity Unbelievable and odd Registered Senior Member

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    whoops.......
    let me scream....

    By the way, John, you seem to have a lot of ideas to pour down today.......
     
  23. John Connellan Valued Senior Member

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    I know, I often go for ages without saying anything then I just get inspired!!!
     

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