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Reporters: Allen June Buenavista Jambee Bernales

KARST. Reporters: Allen June Buenavista Jambee Bernales. KARST PROCESSES & LANDFORMS Karst connotes an assemblage of landforms and the dissolution of a layer or layers of soluble bedrock most common in carbonate rocks (limestone, dolomite) also occurs in evaporites (salts)

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Reporters: Allen June Buenavista Jambee Bernales

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  1. KARST Reporters: Allen June Buenavista Jambee Bernales

  2. KARST PROCESSES & LANDFORMS • Karst connotes an assemblage of landforms and the dissolution of a layer or layers of soluble bedrock • most common in carbonate rocks (limestone, dolomite) • also occurs in evaporites (salts) • also occurs on ice

  3. B. Driving Forces Solution Main reaction: CaCO3 + H2O + CO2 = Ca+2 + 2HCO3- • Factors controlling the solution rate • amount dissolved CO2 • partial pressure of CO2 in air: PCO2 increases, the quantity of CO2 absorbed by water increases • temperature: cooler water is capable of dissolving more CO2 than warmer water at a given PCO2 • biological processes: decaying humus is an important source of CO2

  4. climate • temperature, precipitation, biological activity • runoff generation is the most important effect of climate

  5. C. Resisting Framework Lithology and structure • ideal conditions for a fully developed karst landscape requires limestone that is: • fairly pure; over 60% calcite for some karst; over 90% calcite for fully developed karst landscape • very thick • mechanically strong • massively jointed

  6. POROSITY AND PERMEABILITY • porosity: percentage of pore spaces in a given volume of rock or soil • primary porosity - intergranular voids; affected by: • grain size distribution • particle shape • degree of packing • secondary porosity: voids due to joints, faults, fractures or bedding planes • promotes circulation by increasing permeability

  7. porosity is important only if rocks are also permeable • permeability: ease with which rock or soil transmits water

  8. E. Karst Landforms -Dolines (Sinkholes)

  9. SOLUTION sinkholes Map and Image Image: Tihansky (1999) USGS Circular 1182

  10. SUBSIDENCE sinkholes Image: Tihansky (1999) USGS Circular 1182 • COLLAPSE sinkholes Image: Tihansky (1999) USGS Circular 1182

  11. ho Chocolate Hills, Bohol

  12. Karst Cycle: Cvijic • Requirements: -Thick and extensive mass of limestones/dolostone -underlying impermeable stratum -surface layer of impermeable rock for the initiation of stream pattern.

  13. Karst Cycle: Cvijic • Youth Stage- upper impermeable stream is removed by the streams, which then proceeds to disappear underground through enlarged joints and fractures.

  14. Karst Cycle: Cvijic • Through the youth stage the underground drainage develops slowly and when drainage is all underground MATURITY is reached.

  15. LATE MATURITY- the underground stream reach impermeable underlying stratum and the collapse of the cavern roofs due to lowering of the surface

  16. OLD AGE- all roofs disappear and the drainage reappears at the surface on the exposed impermeable bed.

  17. Karst towers and hills

  18. Geohazards • A poor understanding of Karst terrain has led to land-use practices that pose significant economic and environmental impacts to households and communities. • Sinkhole collapse, either slow or dramatic, regularly causes considerable damage to buildings, highways, rails, bridges, pipelines, storm drains, and sewers. 

  19. sinkholes provide a pathway for surface water to directly enter groundwater aquifers, so the potential for pollution is high because of the minimal filtering of surface water.(permeability of limestone, dolostone, etc.) • Sinkhole formation is closely related to local hydrologic conditions, and human-induced changes to the local hydrology commonly accelerate the process.  • Diverting surface water, pumping groundwater, and constructing reservoirs all contribute to sinkhole collapse. 

  20. Sinkholes regularly cause problems along roads and highways in the Commonwealth.  During the past thirty years, VDOT’s Staunton District has recorded 350 sinkholes that have damaged roads throughout the district. The most notable incidents occurred in the City of Staunton: on August 11, 1911, parts of several homes and the firehouse were lost in a series of sinkholes on Baldwin Street and Central Avenue, and on October 28, 2001, a 45-feet deep chasm opened up on Lewis Street.

  21. Signs of sinkhole formation: • Slumping or falling fence posts • Wilting(bend) vegetation                   • Discolored well water • Structural cracks in walls, floors, or foundations.

  22. THE END….. • BLEHH…………TNX FOR LISTENING!! (‘’,)

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