Water Beneath the Surface

1
Water Beneath the Surface

• Chapter 6.3

2
Distribution of Water Underground

• Much of the water in soil seeps downward until it
  reaches the zone of saturation
• The zone of saturation is the area where water
  fills all of the open spaces in sediment and rock
• Groundwater is water below Earths surface within
  the zone of saturation
• The water table is the upper level of the
  saturation zone of groundwater
• The zone of aeration is the area above the water
  table where the soil, sediment, and rock are not
  saturated with water

3
Movement of Water Underground

• Groundwater moves by twisting and turning
  through interconnected small openings
• The groundwater moves more slowly when the pore
  spaces are smaller
• Porosity is the percentage of pore spaces in rock
• Determines how much groundwater can be stored
• Permeability is the ability to transmit water
  through connected pore spaces
• Aquifers are permeable rock layers or sediments
  that transmit groundwater freely

4
Features Associated with Subsurface Water page
172
5
Water Beneath the Surface

• A spring forms whenever the water table
  intersects the ground surface
• Hot Springs have water that is 69ºC warmer than
  the mean air temperature
• Water is heated by cooling of igneous rock
• Geysers are hot springs that ejects water
• Water turns to steam and erupts

6
Geyser Eruption Cycle
7
Water Beneath the Surface

• A well is a hole bored into the zone of
  saturation
• An artesian well is any formation in which
  groundwater rises on its own under pressure
• Pumping can cause a lowering of the water table
• Pumping can form a cone of depression in the
  water table

8
Cone of Depression
9
Environmental Problems

• Groundwater is being threatened by overuse and
  contamination
• In some regions, the amount of water available to
  recharge an aquifer is less than the amount being
  withdrawn
• Common sources of groundwater pollution are
  sewage from septic tanks, farm wastes, and
  inadequate or broken sewers

10
Caverns

• A cavern is a naturally formed underground
  chamber
• Erosion forms most caverns at or below the water
  table in the zone of saturation
• Travertine (sedimentary rock) is a form of
  limestone that is deposited by hot springs or as
  a cave deposit
• Also known as dripstone

11
Cavern Characteristics

• Formed from calcite deposited as dripping water
  evaporates
• Formed in the zone of aeration
• Common features include stalactites (hanging from
  the ceiling) and stalagmites (growing upward from
  the ground)

12
Karst Topography

• Formed by dissolving rock at, or near, Earths
  surface
• Common features include
• Sinkholes are surface depressions
• Sinkholes form when bedrock dissolves and caverns
  collapse
• Caves and caverns
• Area lacks good surface drainage

13
Sinkhole Formed