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Earth as a System The hydrologic cycle

Earth as a System The hydrologic cycle. Illustrates the circulation of Earth's water supply What processes make up the water cycle?. The hydrologic cycle. Sources of Earth’s water. GROUNDWATER. Largest freshwater reservoir for humans Geological roles

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Earth as a System The hydrologic cycle

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  1. Earth as a SystemThe hydrologic cycle • Illustrates the circulation of Earth's water supply • What processes make up the water cycle?

  2. The hydrologic cycle

  3. Sources of Earth’s water

  4. GROUNDWATER • Largest freshwater reservoir for humans • Geological roles • An erosional agent in the formation of • Sinkholes • Caverns • Equalizes stream flow and surface water

  5. North Avenue – Escalade ???

  6. Cave with stalagmites, stalactites

  7. Groundwater model • http://earthguide.ucsd.edu/earthguide/diagrams/groundwater/

  8. Features associated with subsurface water

  9. 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

  10. 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

  11. 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

  12. 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

  13. Old Faithful geyser in Yellowstone National Park

  14. 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

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

  16. An artesian well resulting from an inclined aquifer

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

  18. 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

  19. 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)

  20. Dripstone formations in Carlsbad Caverns National Park

  21. 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

  22. Development of karst topography

  23. Infrared image of karst topography in central Florida

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