The document discusses karst and hydrothermal processes. It describes how solution processes can dissolve rocks underground and form features like caverns, sinkholes, and disrupted drainage patterns on the surface. This can result in karst topography. Hydrothermal features like hot springs, geysers, and fumaroles are also discussed, and are caused by hot water and steam rising from underground sources. Specific examples of these features in Yellowstone National Park are provided.

1. 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
2© 2011 Pearson Education, Inc.

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
4© 2011 Pearson Education, Inc.
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
6© 2011 Pearson Education, Inc.
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
7© 2011 Pearson Education, Inc.
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
8© 2011 Pearson Education, Inc.
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

10. Karst Topography
• Extent of karst topography
10© 2011 Pearson Education, Inc.Figure 17-6

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
11© 2011 Pearson Education, Inc.
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
12© 2011 Pearson Education, Inc.
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
14© 2011 Pearson Education, Inc.
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
15© 2011 Pearson Education, Inc.
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
16© 2011 Pearson Education, Inc.

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
18© 2011 Pearson Education, Inc.