More Related Content More from lschmidt1170 (20) Ch171. Chapter 17: Karst and
Hydrothermal Processes
McKnight’s Physical Geography:
A Landscape Appreciation,
Tenth Edition, Hess
2. Karst and Hydrothermal
Processes
• The Impact of Solution Processes on the
Landscape
• Solution and Precipitation
• Caverns and Related Features
• Karst Topography
• Hydrothermal Features
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3. The Impact of Solution
Processes on the Landscape
• Mechanical effects of underground water have
limited topographic influence
• Water’s solvent properties allow it to dissolve
certain chemicals from rock
• Hydrothermal vents
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4. Solution and Precipitation
• Water in its pure form is a
poor solvent
• Chemical impurities make
water a good solvent of a
few underground minerals
• Carbonic acid
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Figure 17-1
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 acid
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6. Solution and Precipitation
• Role of bedrock structure
– Profusion of joints allows
for groundwater
penetration
• Precipitation processes
– Mineralized water trickles
along cavern roof or wall
– Reduced air pressure
precipitates mineral
material
– High mineral content in hot
springs
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Figure 17-2
7. Caverns and Related Features
• Large openings beneath
the Earth’s surface that
result from solution
processes
• Often found in areas with
massive limestone deposits
• Two principal stages
– Initial excavation
– Decoration stage:
speleothems
– Stalactites and stalagmites
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Figure 17-3
8. Karst Topography
• Topography that results
from underground
dissolution
• Typical landforms
– Sinkholes
– Disrupted surface
drainage
– Underground drainage
networks
• Ten percent of land
surface is soluble rock
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Figure 17-5
9. Karst Topography
• Sinkholes
– Rounded depressions that
form from dissolution of
surface carbonate rocks
– Collapse dolines
– Wide range of sizes
– Fundamental karst unit of
erosion and weathering
– Chains of sinkholes: uvala
– Tower karst
– Disappearing streams and
swallow holes 9© 2011 Pearson Education, Inc.
Figure 17-9
11. Hydrothermal Features
• Hydrothermal activity
– Geysers and hot springs
• Hot springs
– Water heated by magma
– Forced upward from
pressure resulting from
heating
– Resulting topography from
hot springs
– Algae growth
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Figure 17-10
12. Hydrothermal Features
• Geysers
– Intermittent hot spring
– Accumulation of
superheated water and
steam builds pressure
– Tremendous heat required
for geyser formation
– Variable eruption times
– Variable deposits, most are
sheets of deposits
scattered irregularly over
ground
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Figure 17-12
13. Hydrothermal Features
• Fumaroles
– Surface crack connected to
a deep-seated heat source
– Little water drainage
– Water that is drained is
converted to steam
– Steam issuing vent, either
continuously or
sporadically
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Figure 17-14
14. Hydrothermal Features
• Hydrothermal features in
Yellowstone
– 225 geysers
– Volcanic bedrock materials
– Shallow magma chamber,
mantle plume (heat source)
– Copious summer rain and
winter snowmelt (water
source)
– Numerous fractures and
weak zones from
earthquakes
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Figure 17-13
15. Hydrothermal Features
• Hydrothermal features in
Yellowstone (cont.)
– Geyser basins in same
watershed on west side
of park
– Geyser basins drained
by three rivers
– Geyser basins have
extensive geyserite
– Mammoth Hot Springs
Terraces
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Figure 17-16
16. Summary
• Solution processes are important to the underground
landscape
• Solution processes can also result in hydrothermal
features and karst topography
• Two major soluble rocks, calcium carbonate and
dolomite, are involved in most dissolution processes
• Joints and fractures in the bedrock allow for greater
water percolation and greater dissolution
• Minerals which fall out of solutions that are trickling
along cavern walls or ceilings are called precipitation
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17. Summary
• Numerous cavern features result from solution
processes, which are referred to as speleothems
• Stalactites and stalagmites are common features within
caverns
• Modification of the land surface by subterranean solution
processes results in karst topography
• The most common karst landforms are sinkholes
• Hydrothermal features exist in areas where hot water
moves to the Earth’s surface through openings
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18. Summary
• Hot springs are bubbling basins of hot water that are
heated naturally
• Geysers result from an area of superheated water that
builds up pressure until the water erupts from an
opening
• Fumaroles occur when small amounts of water are
introduced into a hydrothermal vent
• Yellowstone contains the largest percentage of
hydrothermal features in the world
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