Earth as a System The hydrologic cycle

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