Karst Geomorphology

Cave and Karst Glossaries

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Terms: Speology, epigenic, thermokarst, hypogenic karst, limestone, carbonate, dolomite, carbonic acid, corrosion, corrasion, porosity, permeability, hydraulic gradient, groundwater, humus, aquifer, spring, dissapearing stream, hydraulic gradient, karst, thermokarst, solution, sinkhole (doline), tower karst, blind valley, polje, pocket valley, cone karst, uvula, phytokarst

 

Introduction

Definition of karst:

Karst terrain has distinctive characteristics of relief and drainage arising from the solution of soluble bedrock by natural waters. Features of karst terrains may include a variety of sinkholes, solution valleys, underground rivers, caverns, disappearing streams, towers, and distinctive conical hills. Although most karst is developed in limestone (CaCO3) or dolomite (MgCaCO3) it also forms in soluble evaporite deposits.  Karst-like features developed in permafrost by the melting ice is called thermokarst.  Most karst is epigenic, created by carbonic acid  contained in shallow-circulating meteoric waters.  However, some karst cave systems, such as Carlsbad Caverns in New Mexico, are attributed to sulfuric acid associated with deep hydrocabon deposits. This type of karst is refered to a hypogenic karst.  

 Terms:

  • Limestone: A sedimentary rock composed of the mineral calcite.  Limestones are typically deposited in shallow warm water marine environments and arid - semiarid inlands seas and lakes.
  • Corrosion: chemical erosion of rock.  Remember that erosion involves the weathering and removal or rock material.
  • Corrasion: mechanical erosion of rock by a moving agent (e.g water, ice, etc.)
  • Classic Glossary: Cave and Karst Terminology by J.N. Jennings

Conditions contributing to the maximum development of karst

1. Soluble rock at or near the surface (limestone, dolomite, rock salt, gypsum, etc.). Karst is typically associated with carbonates.

2. Dense rock (little interstitial porosity) which is highly jointed.   Solution is facilitated by the concentration of groundwater along joints. If a rock is too porous flow is not locally concentrated and karst development is inhibited. Chalk develops poor karst due to its high porosity.

 3. High hydraulic gradient (h/l) produced by steep topography or entrenched rivers. Moving water corrodes much faster than standing water. The velocity of groundwater is determined by the following equation: V = (K/p)(h/l) where K is the coefficent of permeability, P is effective porosity, h is the head, and l is the length of the groundwater flow path.  All other factor equal the steeper the gradient the fast the flow.  Therefore, a high hydraulic gradient reduces the residence time thereby inhibiting the development of equilibrium between the rock and and surrounding waters.

4. high rainfall:  More water more solution.

 5. high biological activity: As discussed in the weathering lecture, plants, algae, and lichen not only secrete acids but are responsible for increasing the amount of carbonic acid entering the groundwater system. Blue-green algae can produce a surface karst characterized pitting and a sharp-edged spongy lattice of ridges and pinnacles. This epilithic plant-generated karst is called phytokarst.

  •  humus: Decayed organic material increases the acidity of the water by increasing the CO2 content in soils.  Humus also releases organic acids.
  •  Algae: produces phytokarst (an intricately pitted, sharp-edges topography formed by the solution of limestones by acid solvents generated by algae)
  •  Organic waste: Phosphate-rich guano produced by birds and bats strongly corrode limestone.  Rock phosphate produced by the reaction of guano and limestone fills karst cavities, in some cases to a depth of 20 m producing commercial deposits.

 6. Warm Temperatures

  • High temperature: Increases biochemical activity so that more CO2 and organic acids are formed
  • Low temperature: Cold water has a higher potential of becoming more acid
    • Example: 10°C water dissolves 2x more CO2 than 30° water
    • 0°C water dissolves 3x more CO2 than 30° water
    • However, in cold regions dissolution is actually less because
      • there is less CO2 available to dissolve in water due to low biochemical activity,
      • in permafrost regions the water is frozen; acid water is restricted to the upper active layer, and
      • cold water is more viscous and flow is slower.

    7. Pressure:

    • Water under pressure can dissolve more CO2 and therefore hold more CaCO3 in solution
    •  Release of pressure will result in deposition of CaCO3 from water previously under hydraulic pressure (e.g. travertine)
    • Turbulence may also result in deposition (e.g.tufa deposits in rivers)

     8. Mixing of carbonate waters (fig.1)

    • Because of the nonlinear relationship between Ca++ and CO2, an under-saturated, aggressive body of water is produced by the mixing of two saturated water bodies. 

    mixing curve

    Figure 1. Two dissimilar water masses that are saturated relative to CaCO3 are mixed producing an undersaturated mixture which can more aggresively attack carbonate.

  Climate and karst

    Polar Regions: Karst is poorly developed

    • Reasons:
      • Low rainfall and short runoff season
      • Limited infiltration in permafrost regions
      • Cold temperatures result in low biochemical activity.
      • Even though ground water may have large amounts of CO2 it is not particularly aggressive. Why?

     Cold Humid Mid Latitudes: Well developed karst characterized by limestone sinks and closed depressions

     Subhumid and semiarid steppe and savanna grasslands:Little to no karst development

    • Reasons:
      • Very low precipitation
      • During hot dry seasons groundwater tends to move upward and deposit carbonate rather than dissolve it. (Caliche/duricrust: hard crust on arid soils formed by the precipitation of CaCO3
    • **Limestone in arid regions forms ridges and cliffs rivaling sandstone in its stability.

     Tropical Rainforests: Well developed karst characterized by residual hills. Region where karst is best developed.

    karst tower
    Figure 2. Steep karst towers in Guilin China.  (source unknown).
    • Reasons:
      • Very high rainfall
      • Warm temperatures and thick vegetation results in high concentration (partial pressure) of organic acids and CO2
      • Groundwater flows through the ground in large quantities and is very aggressive

    Other controlling factors:

    • Besides climate and lithology, other factors which strongly influence the nature of karst landscapes are: 
      • Base-level fluctuations: caused by tectonic activity or changes in sea level
      • (i.e. eustatic lowering during glaciation)
      •  Structure: solution exploits fracture systems and other planes of weakness that are structurally controlled
      • Stratigraphy: thickness of limestone and permeability of adjacent units
      • Geologic history (is the landscape active, relict, or exhumed?)

    Karst Features 

    Microforms: Grikes, flutes (rillenkarren), solution runnels, solution pits, etc. are formed by runoff on bare surfaces.

    Karst Drainage: Most drainage is subterranean with very few continuous surface streams. Surface drainage patterns tend to be centripital.

      • Unlike most fluvial terrains, which are progressively eroded downward towards baselevel, karst terrains are eroded
        • upward by subsurface abstraction into subterranean drainages and
        • by lateral planation by streams already adjusted to base level

     Dolines/Sinkholes

    Dolines, or sinkholes are enclosed depressions created solution.

    solution doline: Funnel-shaped doline formed by the progressive subsidences as solution progresses along a joint or joint intersection. Regolith drapes the floor of the doline.

     Subsidence doline: Similar to solution doline but overlying soil has washed into a subsuface cave system.

     collapsed doline: Steep-sided sink formed by collapse into a subterranean cavity. An underground cavern forms.  Eventually the overlying rock is longer collapses.

    solution doline

    Figure 3. Solution doline. From Tihansky (1999)

    solution sink Figure 4. Subsidence doline.
       
    sinkhole collapse Figure 5. Collapsed doline. Source: USGS

     Swallow hole (ponors): Limestone sink into which a stream disappears.

     Subjacent karst collapse dolines: Overlying non-carbonate rock collapsed into a limestone cavern

     

     Factors conducive to sinkhole formation:

    • flat land: doline formation is inversely proportional to slope as a result of lower infiltration rates and greater runoff rates.
    • Massive well-jointed limestone
    • C-rich vegetative cover - decaying vegetation provides CO2 and organic acids

    Uvalas (Compound sinkholes): Consist of a series of intersecting dolines

     Karst valleys

    • Blind valley: Well developed valley lacking a stream. Part of an intricate drainage system which is also dry.
    •  Allogenic Valley (formed or originating elsewhere): Deep gorge-like valley formed as a stream flows from a nonkarstic region into a karstic region.
    •  Dry valley: Well developed valley lacking a stream. Commonly part of an intricate drainage systems which is also dry. Forms when a surface-water drainage system becomes diverted underground.
      • Theories on the formation of dry valleys:
        •  Superposition theory
          • Drainage system develops on less permeable rock overlying limestone
          • Drainage system is superimposed on limestone terrane
          • Subterranean drainage forms and valley becomes dry
        •  Base level change
          • Drainage developed with groundwater table close to surface
          • Uplift, lowering of sea level, or local base level by erosion results in lowering of gw table and subterranean migration of surface water 
    • Pocket valley: Valley headed by a large spring
    •  Poljes: Large valleys or lakes with broad valley floors which are oriented along a tectonic trend. Paninsko polje, Slovenia
    • Genetic sequence might be: doline--uvala--poljes?

    Towers and Cones:  characteristic of tropical karst

    • Polygonal karst (cockpit karst): Egg-carton-type topography developed by extensive solution along intersecting joints
    •  Cones, mogotes, & towers: Isolated carbonate hills on a alluvial plain. The plain is either on impermeable bedrock rock or on limestone that has been lowered close to base level.
    • Images of Puerto Ricos tropical karst
    • Tower Karst Halong Bay, Vietnam, images by Sharon Johnson, see also Guilian Photo Album Chinahighlights.com

How are Seti(Search for ExtraTerrestrial Intelligence) and tropical karst related? The Big Dish -located in a cockpit

Interlachen Guilin cockpit mogote
a. Sinkholes @ Interlachen Lake FL b. Karst tower, Guilin, SW China c. Cone and cockpit karst, Puerto Rico d. Mogotes, Puerto Rico
Figure 6 a-e. Google Earth images of karst landscapes from around the world. Click on each image to enlarge.

 

Online Quizzes
Companion Website for Physical Geography: A Landscape Appreciation, Chapter 17: Solution Processes and Karst Topography, 8th Ed,:Tom L. McKnight and Darrel Hess, Michael Ritter Website author URL: http://wps.prenhall.com/esm_mcknight_physgeo_8/0,9340,1445831-,00.html

Online Resources

Classic Dinaric Karst-Slovenia and Montenegro (Yugoslavia)

World Karst

Karst in the United States

Karst Formation

  • Dreybrodt, W. and Gabrovsek, F. 2003. Basic processes and mechanisms governing the evolution of karst. / Speleogenesis and Evolution of Karst Aquifers 1 (1), www.speleogenesis.info , 26 pages, re-published from: Gabrovsek, F. (Ed.), 2002. Evolution of karst: from prekarst to cessation. Postojna-Ljubljana: Zalozba ZRC. 115-154. URL: http://www.speleogenesis.info/archive/publication.php?PubID=4&Type=publication
  • Ford, D.C. 2003. Perspectives in karst hydrogeology and cavern genesis. / Speleogenesis and Evolution of Karst Aquifers 1 (1), www.speleogenesis.info , 12 pages, re-published from: Palmer, A.N., Palmer, M.V., and Sasowsky, I.D. (eds.), 1999. Karst Modeling: Special Publication 5, The Karst Waters Institute, Charles Town, West Virginia (USA), 17-29. URL http://www.speleogenesis.info/archive/publication.php?PubID=1&Type=publication
  • Lugo, Ariel E.; Castro, Leopoldo Miranda; Vale, Abel; López, Tania del Mar; Prieto, Enrique Hernández; Martinó, Andrés García; Rolón, Alberto R. Puente; Tossas, Adrianne G.; McFarlane, Donald A.; Miller, Tom; Rodríguez, Armando; Lundberg, Joyce; Thomlinson, John; Colón, José; Schellekens, Johannes H.; Ramos, Olga; Helmer, Eileen 2001. Puerto Rican Karst-A Vital Resource United States Department of Agriculture Forest Service Gen. Tech. Report WO-65. URL: http://www.treesearch.fs.fed.us/pubs/2864
  • Taylor, Michael Ray, 2006, Subterranean life thrives deep in water system: Researchers find that 'badwater' in Edwards Aquifer is home to an array of life-forms, Houston Chronicle - hypogenic karst
  • Geology and geomorphology of limestone pavements, Limestone pavement action group, URL: http://www.limestone-pavements.org.uk/geology.shtml

Hazards

  • Living on Karst: A Reference Guide for Landowners in Limestone Regions Produced by the Cave Conservancy of the Virginias, URL: http://www.dcr.virginia.gov/dnh/livingonkarst.htm
Exercise

Mammoth Caves Kentucky (USGS shaded Relief map).  Reveiw the description and stratigraphy from my Mammoth Caves National Parks site.  Click on the image to the right enlarge. Print it and   complete the following exercises:

A. Locate and label examples of the following features.

  1. sink hole
  2. compound sink hole (uvala)
  3. karst valley
  4. blind valley
  5. Region of subajacent karst

 

B. Draw the drainage network as indicated by the valleys.  Can you define the direction of regional drainage?  Explain.

 

mammoth


Bibliography

Bloom, Arthur. 2004, Geomorphology, A systematic analysis of Late Cenozoic Landforms, (4th edition): Waveland Press Inc., Longe Grove , IL 482 p.

Barton, Hazel and Luizer Frederick, 2005, Microbial metabolic structure in a sulfidic cave hot spring: Potential mechanisms of biospeleogenesis. Journal of Cave and
Karst Studies, v. 67, no. 1, p. 28-38.

Chorley, R.J., Schumm, S.A., Sugden, D.E., 1984, Geomorphology: Methuen and Co. Ltd., London, 605 p.

Easterbrook, D.L., , 1992, Surface Processes and Landforms, Prentice Hall, Inc., Upper Saddle River, NJ, 546 p.

*Jennings, J.N., 1971, Karst: MIT Press, Cambridge, MA, 252 p.Ritter, D.F., Kochel, C.R., and Miller, J.R., Process Geomorphology (3rd Edition): Wm.C. Brown Publishers, Dubuque, IA, 544 p.

Hill, Carol A., 2000, Overview of the geologic history of cave development in the Guadalupe Mountains, New Mexico. Journal of Cave and Karst Studies 62(2):60-7

Summerfield, M.A., 1991, Global Geomorphology: John Wiley and Sons, New York, NY, 536 p.*Trudgill, S., 1985, Limestone geomorphology: Longman, London, 196 p.

Tihansky, A.B., 1999, Sinkholes, west-central Florida, in Galloway, Devin, Jones D.R., Ingebritsen, S.E., eds., Land subsidence in the United States: U.S. Geological Survey Circular 1182, p. 121-140

USGS, Sinkholes, Water Science for Schools  http://ga.water.usgs.gov/edu/sinkholes.html

  redline Lindley Hanson/Department of Geological Sciences/Salem State College/Geomorphology/GeoIndex/QkRef