1. © 2011 Pearson Education, Inc.
Chapter 9: The Hydrosphere
McKnight’s Physical Geography:
A Landscape Appreciation,
Tenth Edition, Hess

2. © 2011 Pearson Education, Inc.
The Hydrosphere
• The Hydrologic Cycle
• The Oceans
• Movements of Ocean Waters
• Permanent Ice—The Crysophere
• Surface Waters
• Underground Water
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3. © 2011 Pearson Education, Inc.
The Hydrologic Cycle
• Bulk of Earth’s moisture
(99%) is in storage in oceans,
lakes, rivers, glacial ice, or
rocks beneath the surface
• Remaining fraction involved in
a continuous sequence of
movement and change
• Movement is the hydrologic
cycle
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Figure 9-1

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The Hydrologic Cycle
• Three primary movement
types
– Surface to air
• Ocean evaporation
• Vapor remains in air for a
short time
– Air to surface
• Precipitation—78% falls on
oceans and 22% on land
• Precipitation is the same as
evaporation over long time
scales
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Figure 9-2

5. © 2011 Pearson Education, Inc.
The Hydrologic Cycle
• Three primary movement
types (cont.)
– Movement beneath the
surface—runoff
• Water collects in lakes and
rivers and either penetrates
ground or runs off if sloped
• Becomes part of underground
water supply
• Reemerges as springs or
becomes part of rivers and
streams
• Residence times
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Figure 9-3

6. © 2011 Pearson Education, Inc.
The Oceans
• Vast majority of surface is
oceans
• Number of oceans
– Four principal parts
• Pacific—largest, occupies
1/3 of total Earth surface area
• Atlantic—less than half the size
of the Pacific
• Indian—slightly smaller than
Atlantic
• Arctic—small and shallow
• Smaller bodies—seas, gulfs,
and bays
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Figure 9-4

7. © 2011 Pearson Education, Inc.
The Oceans
• Characteristics of ocean
waters
– Chemical composition
• Sodium and chlorine
• Salinity
– Increasing acidity
• Carbon dioxide absorbed by
ocean water creates carbonic
acid
• Affects the ability of microscopic
creatures to build shells and
exoskeletons
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Figure 9-6

8. © 2011 Pearson Education, Inc.
The Oceans
• Characteristics of ocean waters (cont.)
– Temperature
• Decreases with increasing latitude
• Ranges from near 80 °F to near 28 °F
– Density
• High temperature means low density
• High salinity means high density
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Movement of Ocean Waters
• Three primary groupings: tides, currents, and waves
• Tides
– Bulges in sea surface in some places that are
compensated by sinks in the surface at other places
– Significant in shallow water areas for horizontal
placement of water
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Movement of Ocean Waters
• Causes of tides
– Gravitational attraction of
Moon (lunar tides) and Sun
(solar tides)
– More gravitational force on
the side of Earth facing the
Moon
– More centripetal force on
opposite side to keep Earth in
orbit
– Two bulges form on opposite
sides of planet
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Figure 9-7a

11. © 2011 Pearson Education, Inc.
Movement of Ocean Waters
• Causes of tides (cont.)
– Two tidal cycles in 25 hours
– Flood tide and high tide
– Ebb tide and low tide
• Monthly tidal cycles
– Tidal range—difference in
high and low tides
– spring tides
– neap tides
• Global range of tides
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Figure 9-7b and c

12. © 2011 Pearson Education, Inc.
Movement of Ocean Waters
• Currents
– Subtropical gyres develop from surface wind patterns
– Deep ocean circulations
• Result from differences in salinity and temperature in deep ocean
water
• Thermohaline circulation
• Water in northern latitudes is colder and higher salinity, so it sinks
– Global conveyer-belt circulation
• Waves
– Disturbances to the sea surface
– Little forward progress is observed
– Wave breaking can result in shifting of water
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13. © 2011 Pearson Education, Inc.
Movement of Ocean Waters
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Figure 9-10

14. © 2011 Pearson Education, Inc.
Permanent Ice – The Cryosphere
• Cryosphere
– Second greatest storage
of Earth’s water
– Two groups; ice on land
and ice in water
– Approximately 10% of
Earth’s surface is ice
– Different names
• Ice pack
• Ice shelf
• Ice floe
• Iceberg
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Figure 9-12

15. © 2011 Pearson Education, Inc.
Permanent Ice – The Cryosphere
• Cryosphere (cont.)
– Largest ice pack covers
most of the Arctic ocean
surface
– Several large ice shelves
attached to Antarctica
– Large ice floes form off of
Antarctica
• Permafrost
– Permanently frozen
ground ice
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Figure 9-13

16. © 2011 Pearson Education, Inc.
Surface Waters
• Represent only 0.02% of
the world’s total moisture
• Numerous surface water
types
• Lakes—bodies of water
surrounded by land
– Small lakes are called
ponds
– Lake Baykal in Siberia is
largest lake by volume
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Figure 9-17

17. © 2011 Pearson Education, Inc.
Surface Waters
• Lakes (cont.)
– Saline versus freshwater lakes
– Ephemeral lakes (only contain water sporadically)
– Two conditions required for lake formation
• Natural basin with restricted outlet
• Sufficient water to keep basin filled
– Most are relatively short-lived
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18. © 2011 Pearson Education, Inc.
Surface Waters
• Human alteration of natural
lakes
– Irrigation
– Water diversion projects
– Reservoirs
• Artificial lakes used for
hydroelectric power,
municipal water, and stable
agriculture
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Modification of the Aral Sea
Figure 9-19a

19. © 2011 Pearson Education, Inc.
Surface Waters
• Swamps and Marshes
– Flattish places that are
periodically submerged
and shallow enough to
permit plant growth
– Swamps grow trees
– Marshes grow grasses
and rushes
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Figure 9-23

20. © 2011 Pearson Education, Inc.
Surface Waters
• Rivers and Streams
– Streams smaller than
rivers
– Geographers call all
running water streams
– Allow for drainage of
land surface water
towards oceans
– Drainage basins
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Figure 9-24

21. © 2011 Pearson Education, Inc.
Underground Water
• Water beneath land
surface worldwide
• More than half found
within 800 meters of the
surface
• Precipitation or water
basins are the sources
• Quantity held depends on
– Porosity
– Permeability
• Aquifers and aquicludes
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Figure 9-25

22. © 2011 Pearson Education, Inc.
Underground Water
• Zone of aeration
– Topmost band in underground water supply
– Water amount fluctuates rapidly with time
• Zone of saturation
– All pore spaces filled with water, called groundwater
– Top of the zone is the water table
– Water table intersects surface, water flows out (lakes,
swamps, etc.)
– Well water drawn faster than replenished creates a
cone of depression
– Lower limit has absence of pore spaces
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23. © 2011 Pearson Education, Inc.
Underground Water
• Zone of confined water
– Zone that exists in some
regions that is below the
region of impermeable
rock below the zone of
saturation
– Pressure at the great
depth of the water will
cause water to rise to
piezometric surface
– Artesian well versus sub-
artesian
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Figure 9-27

24. © 2011 Pearson Education, Inc.
Underground Water
• Waterless zone
– Pressure too great to
sustain water
• Groundwater mining
– Accumulation of
groundwater is slow, but
human use is rapid
– The Ogallala Aquifer
• Water table drops with
increased use
• Numerous wells tapped
• Unsustainable situation
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Figure 9-30

25. © 2011 Pearson Education, Inc.
Summary
• Most of the water on the planet exists in the oceans
• The hydrologic cycle describes the transition of water
from land to sea to air
• Ocean water has numerous defining characteristics
• Ocean water movement is affected by gravitational
pull from celestial objects (tides)
• Ocean water moves through currents based on
salinity and temperature
• Winds and ocean surface disturbances result in
waves on the ocean surface
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26. © 2011 Pearson Education, Inc.
Summary
• The cryosphere holds a large percentage of the
Earth’s water content
• The ice in the cryosphere contains no salt
• Permafrost is permanently frozen landscape
• Surface water represents a very small fraction of the
total Earth water content
• Surface water processes constitute an important part
of the hydrologic cycle
• Lakes are bodies of water surrounded by land
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27. © 2011 Pearson Education, Inc.
Summary
• Swamps and marshes exist in areas that are shallow
and can support plant life
• Rivers and streams help distribute water back to the
oceans and replenish lakes
• Underground water exists due to water basin seeping
or precipitation
• Human interactions in above ground and below
ground water areas have drastically altered the
hydrosphere
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