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Earth Science, 10e

Earth Science, 10e

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Earth Science, 10e

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  1. Earth Science, 10e Edward J. Tarbuck & Frederick K. Lutgens

  2. Running Water and GroundwaterChapter 4 Earth Science, 10e Stan Hatfield and Ken Pinzke Southwestern Illinois College

  3. Earth as a system: the hydrologic cycle • Illustrates the circulation of Earth's water supply • Processes involved in the cycle • Precipitation • Evaporation • Infiltration • Runoff • Transpiration

  4. The hydrologic cycle

  5. Sources of Earth’s water

  6. Running water • Streamflow • Factors that determine velocity • Gradient, or slope • Channel characteristics • Shape • Size • Roughness • Discharge – volume of water flowing in the stream (generally expresses as cubic feet per second)

  7. Running water • Upstream-downstream changes • Profile • Cross-sectional view of a stream • From head (source) to mouth • Profile is a smooth curve • Gradient decreases from the head to the mouth • Factors that increase downstream • Velocity • Discharge

  8. Running water • Upstream-downstream changes • Profile • Factors that increase downstream • Channel size • Factors that decrease downstream • Gradient, or slope • Channel roughness

  9. Longitudinal profile of a stream

  10. Running water • Base level • Lowest point a stream can erode to • Two general types • Ultimate – sea level • Temporary, or local • Changing causes readjustment of the stream – deposition or erosion

  11. Adjustment of base level to changing conditions

  12. A waterfall is an example of a local base level

  13. Running water • The work of streams • Erosion • Transportation • Transported material is called the stream's load • Dissolved load • Suspended load • Bed load

  14. Running water • The work of streams • Transportation • Load is related to a stream's • Competence - maximum particle size • Capacity - maximum load • Capacity is related to discharge

  15. Running water • The work of streams • Transportation • Deposition • Caused by a decrease in velocity • Competence is reduced • Sediment begins to drop out • Stream sediments • Known as alluvium • Well-sorted deposits

  16. Running water • The work of streams • Transportation • Features produced by deposition • Deltas – exist in ocean or lakes • Natural levees - Form parallel to the stream channel • Area behind the levees may contain back swamps or yazoo tributaries

  17. Structure of a simple delta

  18. Formation of natural levees by repeated flooding

  19. Running water • Stream valleys • Valley sides are shaped by • Weathering • Overland flow • Mass Wasting • Characteristics of narrow valleys • V-shaped • Downcutting toward base level

  20. Running water • Stream valleys • Characteristics of narrow valleys • Features often include • Rapids • Waterfalls • Characteristics of wide valleys • Stream is near base level • Downward erosion is less dominant • Stream energy is directed from side to side

  21. A narrow V-shaped valley

  22. Continued erosion and deposition widens the valley

  23. The resulting wide stream valley is characterized by meandering on a well-developed floodplain

  24. Running water • Stream valleys • Characteristics of wide valleys • Floodplain • Features often include • Meanders • Cutoffs • Oxbow lakes

  25. Erosion and deposition along a meandering stream

  26. A meander loop on the Colorado River

  27. Formation of a cutoff and oxbow lake

  28. Running water • Floods and flood control • Floods are the most common geologic hazard • Causes of floods • Weather • Human interference with the stream system

  29. Running water • Floods and flood control • Engineering efforts • Artificial levees • Flood-control dams • Channelization • Nonstructural approach through sound floodplain management

  30. Satellite view of the Missouri River flowing into the Mississippi River near St. Louis

  31. Same satellite view during flooding in 1993

  32. Running water • Drainage basins and patterns • A divide separates drainage basin • Types of drainage patterns • Dendritic • Radial • Rectangular • Trellis

  33. The drainage basin of the Mississippi River

  34. Drainage patterns

  35. Water beneath the surface (groundwater) • Largest freshwater reservoir for humans • Geological roles • As an erosional agent, dissolving by groundwater produces • Sinkholes • Caverns • An equalizer of stream flow

  36. Water beneath the surface (groundwater) • Distribution and movement of groundwater • Distribution of groundwater • Belt of soil moisture • Zone of aeration • Unsaturated zone • Pore spaces in the material are filled mainly with air

  37. Water beneath the surface (groundwater) • Distribution and movement of groundwater • Distribution of groundwater • Zone of saturation • All pore spaces in the material are filled with water • Water within the pores is groundwater • Water table – the upper limit of the zone of saturation

  38. Features associated with subsurface water

  39. Water beneath the surface (groundwater) • Distribution and movement of groundwater • Distribution of groundwater • Porosity • Percentage of pore spaces • Determines how much groundwater can be stored • Permeability • Ability to transmit water through connected pore spaces • Aquitard – an impermeable layer of material • Aquifer – a permeable layer of material

  40. Water beneath the surface (groundwater) • Features associated with groundwater • Springs • Hot springs • Water is 6-9ºC warmer than the mean air temperature of the locality • Heated by cooling of igneous rock • Geysers • Intermittent hot springs • Water turns to steam and erupts

  41. Old Faithful geyser in Yellowstone National Park

  42. Water beneath the surface (groundwater) • Features associated with groundwater • Wells • Pumping can cause a drawdown (lowering) of the water table • Pumping can form a cone of depression in the water table • Artesian wells • Water in the well rises higher than the initial groundwater level

  43. Formation of a cone of depression in the water table

  44. An artesian well resulting from an inclined aquifer

  45. Water beneath the surface (groundwater) • Environmental problems associated with groundwater • Treating it as a nonrenewable resource • Land subsidence caused by its withdrawal • Contamination

  46. Water beneath the surface (groundwater) • Geologic work of groundwater • Groundwater is often mildly acidic • Contains weak carbonic acid • Dissolves calcite in limestone • Caverns • Formed by dissolving rock beneath Earth's surface • Formed in the zone of saturation

  47. Water beneath the surface (groundwater) • Geologic work of groundwater • Caverns • Features found within caverns • Form in the zone of aeration • Composed of dripstone • Calcite deposited as dripping water evaporates • Common features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor)

  48. Dripstone formations in Carlsbad Caverns National Park

  49. Water beneath the surface (groundwater) • Geologic work of groundwater • Karst topography • Formed by dissolving rock at, or near, Earth's surface • Common features • Sinkholes – surface depressions • Sinkholes form by dissolving bedrock and cavern collapse • Caves and caverns • Area lacks good surface drainage