Karst Definition by Jennings (1985)

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KarstDefinition by Jennings (1985)
A terrain with distinctive landforms and
drainage arising from greater rock solubility in
natural water that is found elsewhere.
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Important Components of Definition

• A distinctive landform developed on highly
  soluble rocks.
• Most often, limestone.
• 60 CaCO3 before karst will start to form.
• 90 CaCO3 before well developed karst will form
• Evaporites (gypsum/halite)
• Quartzite (humid, tropics)

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Important Components of Definition

• A unique drainage pattern resulting from the
  movement of most water into subsurface.
• Holokarst - Precipitation moves directly
  underground little, if any, channelized flow.
• Fluviokarst - clear that karst landforms are
  superimposed on former fluvial landscape.

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Calcite Dissolution
From Ritter et al. (1995)
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Dissolution Reactionsfor Calcite
Equation 1
Equation 2
Equation 3
Equation 4
Summary Equation
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Controls on Solution Rates

• Degree of saturation slow rates close to
  saturation. Change is non-linear.
• Fracture width
• 1 to .1 mm flow is laminar dissolution rate
  based on discharge of water through fracture.
• gt5 mm flow may be turbulent dissolution rate
  based on rate of chemical reactions at surface of
  mineral grain.
• 1-5mm varies with site conditions combination
  of two.
• Other Factors Pco2 temperature of water

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Solution Rates
From Ritter et al. (1995)
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Karst LandformsHumid, Temperature Climates

• Dolines (sinkholes) small, shallow depression
  commonly wider than they are deep.
• Solution Sinkhole related to subcutaneous zone
• Collapse Sinkhole material fails into subsurface
  cavity previously created by dissolution
• Uvala large closed depression formed by
  coalescence of one or more dolines.
• Karst Plain A plain composed of closed
  depressions and subterranean drainage in karst
  region.
• Swallet (swallow hole) A place where water
  disappears underground in karst region. Swallet
  commonly used to describe loss of water in stream
  bed.

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Solution Sinkhole Development
From Ritter et al. (1995)
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Collapse Sinkhole
From Ritter et al. (1995)
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Sinkhole Plain
From Ritter et al. (1995)
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Blind and Dry Valleys
From Ritter et al. (1995)
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Karst LandformsHumid, Temperature Climates

• Blind Valley A valley that end abruptly where
  stream vanishes underground.
• Sinking Stream stream that vanishes underground,
  usually at terminus of blind valley.
• Resurgence point where waters from sinking
  stream reemerges from underground.
• Dry Valley Valley that no longer exhibits
  channelized flow.
• Cave A natural underground room or series of
  rooms large enough to be entered by a person.

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Karst LandformsHumid, Tropical Climates

• Cockpit Karst a conglomeration of closed
  depressions surrounded by conical hills - similar
  to cone karst where depression are star-shaped.
• Tower karst Type of karst characterized by
  isolated, steep-walled hills separated by flat
  lying plain of alluvium.

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Cave Shapes(Reach Scale)
From Ritter et al. (1995)
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Cave Patterns
From Ritter et al. (1995)
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Cave Characteristics

• Vadose Caves
• Flow always moves downward along easiest route
• Governed largely by rock structure
• Dominated by canyons and shafts
• Caves tend not to converge unless forced to by
  rock structure

• Phreatic Caves
• Caves may descend well below water table and then
  rise to level of water table
• Tend to cut across rock structure
• Dominated by elliptical tubes
• Caves tend to converge , developing along
  hydraulic efficient paths