Groundwater and karst topography

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Groundwater and karst topography

• 1 factor in geoenvironmental problems of the
  Nittany Valley

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Karst topography dissolution of limestone along
fractures

• CO2 H2O H2CO3 (acid)
• H2CO3 CaCO3 Ca2 2 HCO3-
• Produces 50-100 mg/L Ca HCO3 ions dissolved in
  groundwater these are carried away, perpetuating
  the dissolution.
• Collapse of land surface above caverns forms a
  KARST topography

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Nittany Valley karst features
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Small-scale cavity formation in the Salona
Formation
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Two possible scenarios of sinkhole subsidence

• (a) collapse above caves
• (b) washout of plugs above chimneys to cave
  systems
• Almost always, sinkhole collapse is NOT a problem
  if the underground caverns are below the water
  table or if groundwater flow is not downward.
  And in all cases, the caves are preexisting.

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Sinkhole cavity overlain by bedrock roof
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Tussey Sink
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Former Beaver Stadium sinkhole
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Nittany Mall sinkholes
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Sinkhole cavity connected to the near-surface by
a chimney
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Flow of groundwater can be predicted from
hydrogeologic measurements in wells and some math
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k is permeability (ability to transport water).
Note last column, and relatively rapid transport
in karst limestone
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Accelerated transport therefore solution in
zones of fractures
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A fracture trace Big Hollow
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Example of an environmental problem Pb from a TV
tube factory