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Ch09 Ch09 Presentation Transcript

  • © 2011 Pearson Education, Inc.Chapter 9: The HydrosphereMcKnight’s Physical Geography:A Landscape Appreciation,Tenth Edition, Hess
  • © 2011 Pearson Education, Inc.The Hydrosphere• The Hydrologic Cycle• The Oceans• Movements of Ocean Waters• Permanent Ice—The Crysophere• Surface Waters• Underground Water2
  • © 2011 Pearson Education, Inc.The Hydrologic Cycle• Bulk of Earth’s moisture(99%) is in storage in oceans,lakes, rivers, glacial ice, orrocks beneath the surface• Remaining fraction involved ina continuous sequence ofmovement and change• Movement is the hydrologiccycle3Figure 9-1
  • © 2011 Pearson Education, Inc.The Hydrologic Cycle• Three primary movementtypes– Surface to air• Ocean evaporation• Vapor remains in air for ashort time– Air to surface• Precipitation—78% falls onoceans and 22% on land• Precipitation is the same asevaporation over long timescales4Figure 9-2
  • © 2011 Pearson Education, Inc.The Hydrologic Cycle• Three primary movementtypes (cont.)– Movement beneath thesurface—runoff• Water collects in lakes andrivers and either penetratesground or runs off if sloped• Becomes part of undergroundwater supply• Reemerges as springs orbecomes part of rivers andstreams• Residence times5Figure 9-3
  • © 2011 Pearson Education, Inc.The Oceans• Vast majority of surface isoceans• Number of oceans– Four principal parts• Pacific—largest, occupies1/3 of total Earth surface area• Atlantic—less than half the sizeof the Pacific• Indian—slightly smaller thanAtlantic• Arctic—small and shallow• Smaller bodies—seas, gulfs,and bays6Figure 9-4
  • © 2011 Pearson Education, Inc.The Oceans• Characteristics of oceanwaters– Chemical composition• Sodium and chlorine• Salinity– Increasing acidity• Carbon dioxide absorbed byocean water creates carbonicacid• Affects the ability of microscopiccreatures to build shells andexoskeletons7Figure 9-6
  • © 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 density8
  • © 2011 Pearson Education, Inc.Movement of Ocean Waters• Three primary groupings: tides, currents, and waves• Tides– Bulges in sea surface in some places that arecompensated by sinks in the surface at other places– Significant in shallow water areas for horizontalplacement of water9
  • © 2011 Pearson Education, Inc.Movement of Ocean Waters• Causes of tides– Gravitational attraction ofMoon (lunar tides) and Sun(solar tides)– More gravitational force onthe side of Earth facing theMoon– More centripetal force onopposite side to keep Earth inorbit– Two bulges form on oppositesides of planet10Figure 9-7a
  • © 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 inhigh and low tides– spring tides– neap tides• Global range of tides11Figure 9-7b and c
  • © 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 oceanwater• 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 water12
  • © 2011 Pearson Education, Inc.Movement of Ocean Waters13Figure 9-10
  • © 2011 Pearson Education, Inc.Permanent Ice – The Cryosphere• Cryosphere– Second greatest storageof Earth’s water– Two groups; ice on landand ice in water– Approximately 10% ofEarth’s surface is ice– Different names• Ice pack• Ice shelf• Ice floe• Iceberg14Figure 9-12
  • © 2011 Pearson Education, Inc.Permanent Ice – The Cryosphere• Cryosphere (cont.)– Largest ice pack coversmost of the Arctic oceansurface– Several large ice shelvesattached to Antarctica– Large ice floes form off ofAntarctica• Permafrost– Permanently frozenground ice15Figure 9-13
  • © 2011 Pearson Education, Inc.Surface Waters• Represent only 0.02% ofthe world’s total moisture• Numerous surface watertypes• Lakes—bodies of watersurrounded by land– Small lakes are calledponds– Lake Baykal in Siberia islargest lake by volume16Figure 9-17
  • © 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-lived17
  • © 2011 Pearson Education, Inc.Surface Waters• Human alteration of naturallakes– Irrigation– Water diversion projects– Reservoirs• Artificial lakes used forhydroelectric power,municipal water, and stableagriculture18Modification of the Aral SeaFigure 9-19a
  • © 2011 Pearson Education, Inc.Surface Waters• Swamps and Marshes– Flattish places that areperiodically submergedand shallow enough topermit plant growth– Swamps grow trees– Marshes grow grassesand rushes19Figure 9-23
  • © 2011 Pearson Education, Inc.Surface Waters• Rivers and Streams– Streams smaller thanrivers– Geographers call allrunning water streams– Allow for drainage ofland surface watertowards oceans– Drainage basins20Figure 9-24
  • © 2011 Pearson Education, Inc.Underground Water• Water beneath landsurface worldwide• More than half foundwithin 800 meters of thesurface• Precipitation or waterbasins are the sources• Quantity held depends on– Porosity– Permeability• Aquifers and aquicludes21Figure 9-25
  • © 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 acone of depression– Lower limit has absence of pore spaces22
  • © 2011 Pearson Education, Inc.Underground Water• Zone of confined water– Zone that exists in someregions that is below theregion of impermeablerock below the zone ofsaturation– Pressure at the greatdepth of the water willcause water to rise topiezometric surface– Artesian well versus sub-artesian23Figure 9-27
  • © 2011 Pearson Education, Inc.Underground Water• Waterless zone– Pressure too great tosustain water• Groundwater mining– Accumulation ofgroundwater is slow, buthuman use is rapid– The Ogallala Aquifer• Water table drops withincreased use• Numerous wells tapped• Unsustainable situation24Figure 9-30
  • © 2011 Pearson Education, Inc.Summary• Most of the water on the planet exists in the oceans• The hydrologic cycle describes the transition of waterfrom land to sea to air• Ocean water has numerous defining characteristics• Ocean water movement is affected by gravitationalpull from celestial objects (tides)• Ocean water moves through currents based onsalinity and temperature• Winds and ocean surface disturbances result inwaves on the ocean surface25
  • © 2011 Pearson Education, Inc.Summary• The cryosphere holds a large percentage of theEarth’s water content• The ice in the cryosphere contains no salt• Permafrost is permanently frozen landscape• Surface water represents a very small fraction of thetotal Earth water content• Surface water processes constitute an important partof the hydrologic cycle• Lakes are bodies of water surrounded by land26
  • © 2011 Pearson Education, Inc.Summary• Swamps and marshes exist in areas that are shallowand can support plant life• Rivers and streams help distribute water back to theoceans and replenish lakes• Underground water exists due to water basin seepingor precipitation• Human interactions in above ground and belowground water areas have drastically altered thehydrosphere27