How does permeable and impermeable rock have an effect on a river?

December 28, 2005 2 Comments
Hattie asked:

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Tags: , Geography
2 Comments to “How does permeable and impermeable rock have an effect on a river?”
  1. arundhati says:

    m nt sure but in upper course the water will flow wid d usual speed but whn it passes through the lower course the flow as in d speed will change cuz it has permeable rock

  2. Sandgroper says:

    An impermeable substance means that it has porosity, and that porosity is connected. This allows a liquid to flow through the material.

    So yes, soil and sand would be examples of permeable materials, as they allow water to filter through them.

    However, in a more geologic sense (and found underground at depth), what we would be looking at is the actual rocks. Rocks that have permeability include sedimentary rocks such as sandstones, conglomerates, and (to a slightly lesser degree) shales. This permeable characteristic of sandstone is actually one of the reasons why it is a great reservoir for petroleum (oil) deposits.

    Impermeable substances would include most igneous and metamorphic rocks (ex. granite, basalt, marble, schist, gneiss, etc…). These rocks don’t usually have any porosity in them and therefore are unable to be permeable. Some extrusive igneous rocks (such as pumice or vesicular basalt) can show porosity due to gas escaping upon rapid cooling, however these pore spaces are rarely interconnected, therfore they are still not permeable rocks.

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