Water Underground S6E3 Students will recognize the significant role of water in Earth processes.

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Water Underground S6E3 Students will recognize
the significant role of water in Earth processes.

• S6E3.a Explain that a large portion of the
  Earths surface is water, consisting of oceans,
  rivers, lakes, underground water, and ice.

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What you will learn in the section

• Identify and describe the location of the water
  table.
• Describe an aquifer.
• Explain the difference between a spring and a
  well.
• Explain how caves and sinkholes form as a result
  of erosion and deposition.

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A family lives 50 km from the nearest stream or
lake and gets water from a well. Where does the
water in the well come from?

• It comes from water stored underground.

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• Groundwater is water located within the rocks
  below the Earths surface.
• FYI (do not write)
• Millions of people get their water from
  groundwater.
• Groundwater not only is an important resource but
  also plays an important role in erosion and
  deposition.

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Location of Groundwater

• Water is found underground in an area between two
  zones. Rainwater passes through the upper zone,
  called the zone of aeration. Farther down, the
  water collects in an area called the zone of
  saturation. In this zone, the spaces between the
  rock particles are filled with water.
• The two zones meet at a boundary known as the
  water table.
• Rises during wet seasons and falls during dry
  seasons

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Aquifers

• The rock layer that stores groundwater and allows
  the flow of groundwater is called an aquifer.
• The more open spaces, or pores, between particles
  in an aquifer, the more water the aquifer can
  hold.
• The percentage of open space between individual
  rock particles in a rock layer is called
  porosity.

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• If the pores of a rock layer are connected,
  groundwater can flow through the rock layer. A
  rocks ability to let water pass through is
  called permeability. A rock that stops the flow
  of water is impermeable.

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• The best aquifers usually form in permeable
  materials, such as sandstone, limestone, or
  layers of sand and gravel.
• Some aquifers cover very large areas.
• They are important source of water for cities and
  agriculture.
• The ground surface where water enters an aquifer
  is called the recharge zone.
• The size of the recharge zone depends on how
  permeable rock is at the surface.

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Aquifer in the United States
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Aquifers in Georgia
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Springs and Wells

• Groundwater movement is determined by the slope
  of the water table. Moves down slope.
• If the water table reaches the Earths surface,
  water will flow out from the ground and will form
  a spring.
• Springs are an important source of drinking
  water.
• Where the water table is higher than the Earths
  surface, lakes will form.

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• Wells are human-made holes that are deeper than
  the level of the water table.
• If it is not deep enough, it will dry up when the
  water table falls below the bottom of the well.
• If an area has too many wells, groundwater can be
  removed too rapidly which can cause the wells to
  run dry.

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Artesian Springs

• A sloping layer of permeable rock sandwiched
  between two layers of impermeable rock is called
  an artesian formation.
• The permeable rock is an aquifer and the top
  layer of impermeable rock is called a cap rock.
• Artesian spring is a spring whose water flows
  from a crack in the cap rock of the aquifer.
• These are sometimes found in deserts, where they
  are the only source of water.
• Most have cool water but some springs have hot
  water.

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Formation of Caves

• Water erosion creates most caves found along
  coastal areas.
• Waves crashing against the rock over years wears
  away part of the rock forming a cave.
• Inland caves are also formed by water erosion-in
  particular, groundwater eroding limestone.
• As the limestone dissolves, underground
  passageways and caverns are formed.

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The Caves of Belize Caves Branch Cave
The Caves at Norman Island
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Sinkholes

• Sinkholes are common where the rock below the
  land surface is limestone, carbonate rock, salt
  beds, or rocks that can naturally be dissolved by
  ground water circulating through them.
• As the rock dissolves, spaces and caverns
  develop underground.
• Sinkholes are dramatic because the land usually
  stays intact for a while until the underground
  spaces just get too big.
• If there is not enough support for the land above
  the spaces then a sudden collapse of the land
  surface can occur.
• The most damage from sinkholes tends to occur in
  Florida, Texas, Alabama, Missouri, Kentucky,
  Tennessee, and Pennsylvania.

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Nixa, Missouri 60 feet in diameter and 75 feet
deep
Sinkhole - Guatemala 330 ft deep