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Question About Water

  1. Dec 28, 2004 #1


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    What makes water such a powerful force (if not the most powerful force) on Earth? Or is water a powerful force regardless of atmosphere, planet, etc.?

    This may be a stupid question, but I'd really like someone to explain this to me if they can. Its a question that I have no been able to figure out myself.

    Any help is greatly appreciated.
  2. jcsd
  3. Dec 29, 2004 #2


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    Can you please elaborate on what you mean by a powerful force? Are you talking in terms of an erosional force like a river (or glacier), a destructive force like the recent tsunami in Asia, an atmospheric force like its role in storm formation, its ability to support life on this planet, or other things?
  4. Dec 30, 2004 #3
    Water is not a force. The energy of the sun and geothermal energy are the main forces that drive the dynamics of Earth. Water is just the medium by which those sources conduct energy.
  5. Dec 30, 2004 #4


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    All of the above really. Sorry I wasn't more specific in my original post.
  6. Dec 30, 2004 #5


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    Water has a density of 1000 kg/m3, and then multiply that by 100's or 1000's of m3 - that is a lot of mass. If the mass is moving - that produces a lot of momentum, that when it impacts a non-moving object, produces a lot of force.

    Also remember, wind, which has a density of about 1.25 kg/m3 (or 800 times less than water), can exert significant force at high enough velocity.

    As for erosion, it is a continuous process. In the case of water or air, suspend solids (sand or soil, pebbles, stones, rocks, boulders in water and dust or sand in air) assist the erosion process.

    It's a matter of mass and momentum.
    Last edited: Dec 30, 2004
  7. Dec 30, 2004 #6


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    Some quick math:

    If a section of the tsunami was an average of 10m high, 300m long, and 1000m wide, that's 3 billion kg of water. At a speed of 10m/s, that's 150 billion joules of energy. A ton of TNT contains about 4 billion joules of energy, so that's ~37 tons of TNT. Put another way, pile pickup-truckloads of TNT every 27 meters along the beach and you have a rough approximation of the energy contained in all that moving water.

    One thing to note, when a ton of TNT explodes, the energy goes in all directions (including up). When the wave hits, all the energy goes in the same direction, so its actually even more.
    Last edited: Dec 30, 2004
  8. Dec 30, 2004 #7


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    If the oceans were filled with oil, or alcohol, or mercury, a tsunami would be no less devastating.

    As an agent of erosion, water is pretty good because it dissolves many salts, and also because it expands upon freezing. Hydrochloric acid would probably be much more erosive (not to add corrosive) than water.

    In short, water is not a powerful force in the way you think it is. This is merely folklore passed on from the ancients.

    However, water is beautifully suited to propagating life on earth. It exhibits all three states at ambient temperatures. It is a great solvent for inorganic salts yet perfectly harmless to organic stuff. It has a huge specific heat capacity. It expands on freezing. And it's a colorless liquid, among several other things.
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