The document summarizes key aspects of the hydrosphere including the hydrologic cycle, oceans, ocean water movement, permanent ice, surface waters, and underground water. It explains that most water exists in oceans and a small fraction cycles through evaporation and precipitation. Ocean waters have varying characteristics and move via tides, currents, and waves. Surface waters include lakes, swamps, rivers and streams, while underground water exists in aquifers below ground. Human activities have significantly impacted both surface and subsurface waters.

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

4. © 2011 Pearson Education, Inc.
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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9. © 2011 Pearson Education, Inc.
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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10. © 2011 Pearson Education, Inc.
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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