Structure of Aquifers mix copy

Learning outcomes: to describe the structure of confined and unconfined aquifers; to explain the properties of rocks that form aquifers using the correct key terms

Environmental Scienceaquifers
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Structure of Aquifers mix copy

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Learning outcomes: to describe the structure of confined and unconfined aquifers; to explain the properties of rocks that form aquifers using the correct key terms
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Slide Content
  1. Aquifers

    Slide 1 - Aquifers

    • Structure and rock types
  2. Section aims

    Slide 2 - Section aims

    • In this section you will learn about
    • Porosity
    • Permeability
    • The structure of aquifer confined and unconfined aquifers
  3. The base of the aquifer

    Slide 3 - The base of the aquifer

    • If you wanted to hold some water what would you use?
    • You probably suggested a glass, or a bucket, but whatever it was it has the ability to stop water leaking away.
    • This is called impermeability. Fluid is unable to pass through an impermeable surface.
    • The definition of permeability is therefore, the rate of flow of a liquid through a material.
    • The base of an aquifer must therefore have an impermeable layer of rock.
  4. The confining rock

    Slide 4 - The confining rock

    • The base of the aquifer has a confining layer of impermeable rock.
    • Impermeable rocks are made up of fine, interconnected particles, so water cannot pass through. Examples are: clay, granite, basalt.
    • Granite
    • Confining layer
  5. Aquifer rock

    Slide 5 - Aquifer rock

    • Sandstone
    • Soil
    • Confining layer
    • Porous rock
    • Recharge area
    • The rock that stores the water needs to have plenty of pore spaces between the particles or fractures. The rock therefore needs to have a high porosity or be pervious. Examples of rocks that make good aquifers are: sandstone, chalk, fractured limestone and gravels. The definition of porosity is the ratio of pore spaces to the total volume. A pervious rock allows water through fractures and bedding planes.
  6. Confined aquifer

    Slide 6 - Confined aquifer

    • If there is a second layer of impermeable rock then this is called a confined aquifer. Water will be under pressure and so will not need to be pumped. An unconfined aquifer does not have this second impermeable layer and needs to be pumped out.
    • Confining layer
    • Confining layer
    • Confined aquifer
    • Unconfined aquifer
    • Recharge area
    • Recharge area
    • Recharge area
  7. Recap  Make sure you understand and can define these terms.

    Slide 7 - Recap Make sure you understand and can define these terms.

    • Permeability. A property of soils and rocks indicating their capacity for transmitting water, because of their porosity and /or perviousness.
    • A permeable rock allows water/fluids to enter because it is either porous OR permeable OR both 
    • Porosity. The percentage of air spaces in a certain types of soil or rock indicating how much water / fluids it could contain
    • A porous rock has air space into which water can flow e.g. chalk, sandstone
    • Pervious. The property of rocks indicating their ability to allow water to pass through their joints or bedding planes.
    • A pervious rock does NOT have air space into which water can flow, but DOES HAVE joints or bedding planes along which water can flow e.g. limestone
    • Impermeable rocks do NOT have air spaces or bedding planes through which water can enterer.
    • An impermeable rock cannot hold water e.g. clays, unjointed granite
    • Confined aquifer – has an impermeable layer above the aquifer and so is under pressure
    • Unconfined aquifer – has a single impermeable layer at the bottom and needs to be pumped