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Earth Science, 13e

Earth Science, 13e. Tarbuck & Lutgens. Running Water and Groundwater Earth Science, 13e Chapter 5. Stanley C. Hatfield Southwestern Illinois College. Earth as a system: the hydrologic cycle. Illustrates the circulation of Earth’s water supply Processes involved in the cycle

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Earth Science, 13e

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  1. Earth Science, 13e Tarbuck & Lutgens

  2. Running Water and GroundwaterEarth Science, 13eChapter 5 Stanley C. Hatfield 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. Running water • Drainage basin • Land area that contributes water to a river system • A divide separates drainage basins

  6. Drainage basins and divides

  7. 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)

  8. 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

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

  10. Longitudinal profile of a stream

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

  12. 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

  13. 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

  14. 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

  15. Formation of natural levees by repeated flooding

  16. 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

  17. Adjustment of base level to changing conditions

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

  19. 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

  20. V-shaped valley of the Yellowstone River

  21. Continued erosion and deposition widens the valley

  22. Characteristics of a wide stream valley

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

  24. A meander loop on the Colorado River

  25. Running water • Drainage patterns • Networks of streams that from distinctive patterns • Types of drainage patterns • Dendritic • Radial • Rectangular • Trellis

  26. Drainage patterns

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

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

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

  30. Same satellite view during flooding in 1993

  31. 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

  32. 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

  33. 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

  34. Features associated with subsurface water

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

  36. Water beneath the surface (groundwater) • Features associated with groundwater • Springs • Hot springs • Water is 6–9° C (10–15° F) 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

  37. Old Faithful geyser in Yellowstone National Park

  38. 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

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

  40. Artesian systems

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

  42. 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

  43. 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)

  44. Cave features in Carlsbad Caverns National Park

  45. 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

  46. Features of karst topography

  47. End of Chapter 5

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