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  1. 1. Chapter 17: Karst andHydrothermal ProcessesMcKnight’s Physical Geography:A Landscape Appreciation,Tenth Edition, Hess
  2. 2. Karst and HydrothermalProcesses• The Impact of Solution Processes on theLandscape• Solution and Precipitation• Caverns and Related Features• Karst Topography• Hydrothermal Features2© 2011 Pearson Education, Inc.
  3. 3. The Impact of SolutionProcesses on the Landscape• Mechanical effects of underground water havelimited topographic influence• Water’s solvent properties allow it to dissolvecertain chemicals from rock• Hydrothermal vents3© 2011 Pearson Education, Inc.
  4. 4. Solution and Precipitation• Water in its pure form is apoor solvent• Chemical impurities makewater a good solvent of afew underground minerals• Carbonic acid4© 2011 Pearson Education, Inc.Figure 17-1
  5. 5. Solution and Precipitation• Dissolution– Most effective on carbonate sedimentary rocks (i.e.,limestone)– Calcium carbonate reaction• CaCO3 + H2O + CO2 = Ca(HCO3)2– Dolomite reaction• CaMg(CO3)2 + 2H2O + 2CO2 = Ca(HCO3)2 + Mg(HCO3)2– These are most notable dissolution processes– Occurs more rapidly in humid regions– Possible role of sulfuric acid5© 2011 Pearson Education, Inc.
  6. 6. Solution and Precipitation• Role of bedrock structure– Profusion of joints allowsfor groundwaterpenetration• Precipitation processes– Mineralized water tricklesalong cavern roof or wall– Reduced air pressureprecipitates mineralmaterial– High mineral content in hotsprings6© 2011 Pearson Education, Inc.Figure 17-2
  7. 7. Caverns and Related Features• Large openings beneaththe Earth’s surface thatresult from solutionprocesses• Often found in areas withmassive limestone deposits• Two principal stages– Initial excavation– Decoration stage:speleothems– Stalactites and stalagmites7© 2011 Pearson Education, Inc.Figure 17-3
  8. 8. Karst Topography• Topography that resultsfrom undergrounddissolution• Typical landforms– Sinkholes– Disrupted surfacedrainage– Underground drainagenetworks• Ten percent of landsurface is soluble rock8© 2011 Pearson Education, Inc.Figure 17-5
  9. 9. Karst Topography• Sinkholes– Rounded depressions thatform from dissolution ofsurface carbonate rocks– Collapse dolines– Wide range of sizes– Fundamental karst unit oferosion and weathering– Chains of sinkholes: uvala– Tower karst– Disappearing streams andswallow holes 9© 2011 Pearson Education, Inc.Figure 17-9
  10. 10. Karst Topography• Extent of karst topography10© 2011 Pearson Education, Inc.Figure 17-6
  11. 11. Hydrothermal Features• Hydrothermal activity– Geysers and hot springs• Hot springs– Water heated by magma– Forced upward frompressure resulting fromheating– Resulting topography fromhot springs– Algae growth11© 2011 Pearson Education, Inc.Figure 17-10
  12. 12. Hydrothermal Features• Geysers– Intermittent hot spring– Accumulation ofsuperheated water andsteam builds pressure– Tremendous heat requiredfor geyser formation– Variable eruption times– Variable deposits, most aresheets of depositsscattered irregularly overground12© 2011 Pearson Education, Inc.Figure 17-12
  13. 13. Hydrothermal Features• Fumaroles– Surface crack connected toa deep-seated heat source– Little water drainage– Water that is drained isconverted to steam– Steam issuing vent, eithercontinuously orsporadically13© 2011 Pearson Education, Inc.Figure 17-14
  14. 14. Hydrothermal Features• Hydrothermal features inYellowstone– 225 geysers– Volcanic bedrock materials– Shallow magma chamber,mantle plume (heat source)– Copious summer rain andwinter snowmelt (watersource)– Numerous fractures andweak zones fromearthquakes14© 2011 Pearson Education, Inc.Figure 17-13
  15. 15. Hydrothermal Features• Hydrothermal features inYellowstone (cont.)– Geyser basins in samewatershed on west sideof park– Geyser basins drainedby three rivers– Geyser basins haveextensive geyserite– Mammoth Hot SpringsTerraces15© 2011 Pearson Education, Inc.Figure 17-16
  16. 16. Summary• Solution processes are important to the undergroundlandscape• Solution processes can also result in hydrothermalfeatures and karst topography• Two major soluble rocks, calcium carbonate anddolomite, are involved in most dissolution processes• Joints and fractures in the bedrock allow for greaterwater percolation and greater dissolution• Minerals which fall out of solutions that are tricklingalong cavern walls or ceilings are called precipitation16© 2011 Pearson Education, Inc.
  17. 17. Summary• Numerous cavern features result from solutionprocesses, which are referred to as speleothems• Stalactites and stalagmites are common features withincaverns• Modification of the land surface by subterranean solutionprocesses results in karst topography• The most common karst landforms are sinkholes• Hydrothermal features exist in areas where hot watermoves to the Earth’s surface through openings17© 2011 Pearson Education, Inc.
  18. 18. Summary• Hot springs are bubbling basins of hot water that areheated naturally• Geysers result from an area of superheated water thatbuilds up pressure until the water erupts from anopening• Fumaroles occur when small amounts of water areintroduced into a hydrothermal vent• Yellowstone contains the largest percentage ofhydrothermal features in the world18© 2011 Pearson Education, Inc.