The Action of Groundwater

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The Action of Groundwater

• Earth Science
• Grade 8

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Groundwater

• The water that soaks into the ground and collects
  in pores is called groundwater.
• Rocks have varying amounts of pore space.
• If they allow water into them, they are called
  permeable.
• If they do not allow water into them then they
  are called impermeable.

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Groundwater

• Groundwater will continue to go lower into the
  ground (by the force of gravity), until it
  reaches a layer of impermeable rock.
• This acts like a dam, and the water does not move
  any further.
• The water fills in all of the pore space of the
  permeable rocks.

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Groundwater

• A layer of rock that allows the water into it,
  and also allows the water to flow through it is
  called an aquifer.
• A layer that is completely filled with water is
  called the zone of saturation.
• The very top of this zone is called the water
  table. This location varies from place to place.
• The area above this zone is called the zone of
  aeration. It is filled with air, except after a
  rain when the water moves through it on its way
  to the saturated layer.

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Groundwater

• If you were going to dig a well for your house,
  you would have to dig deep enough to reach the
  zone of saturation. Otherwise you would not
  always have water.
• If too many people dig wells in similar
  locations, there is a chance the well would run
  dry-which means that there is no more water
  available.

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Groundwater Diagram
(Zone of aeration)
(Lake)
(Zone of saturation)
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Groundwater

• Most of the time you need a pump to get the water
  to the surface (from the zone of saturation).
• A special case called an artesian well -there is
  no need for a pump. The water moves up by
  itself.

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Aquifer and Artesian well
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Groundwater

• Sometimes the land dips low enough to reach the
  water table level. Water that flows to the
  surface here are called springs.
• They are what feeds many of our rivers and lakes.
  If the land around those springs is heated (near
  a volcano or magma), they heat the water it
  becomes a hot spring.

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Springs and Hot springs
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Groundwater

• A special type of Hot spring is one that erupts
  periodically. This is called a geyser.
• The most famous of this type of hot spring is Old
  Faithful in Yelllowstone National Park. It
  shoots out nearly 12,000 gallons of water every
  60-90 minutes.

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Geysers
Old Faithful, Yellowstone
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Groundwater

• As groundwater travels it will eat away at some
  of the softer rocks in the ground. Sometimes it
  can eat away so much of an area that it will
  create a cave.
• Inside this area it is very cool and very wet.
  The walls constantly have moisture on them.

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Caves
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Groundwater

• The water contains dissolved materials, which
  build up and form new mounds of rock
• When they build up from the ground, they are
  called stalagmites.
• When they hang from the ceiling, they are called
  stalactites.
• Sometimes the two shall meet, which we call a
  column.

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Stalactites, stalagmites, columns
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Groundwater

• If the cave becomes large enough or it is close
  enough to the surface, the land above it may
  become unstable.
• If the cave collapses, it will create a sinkhole.

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Sinkholes
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Sinkholes
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Sinkholes
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How do pot holes form?

• video

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Neshaminy Falls Picture by Bill Heasley