2. Earth as a System: The Hydrologic Cycle
Illustrates the circulation of Earth’s water supply
Most water is in the oceans

3. Earth as a System: The Hydrologic Cycle
Processes involved in the water cycle
Precipitation
Evaporation
Infiltration
Runoff
Transpiration

4. The Hydrologic Cycle

5. Running Water Drainage basin Divide
Land area that contributes water to a river system
Divide
Separates drainage basins

6. Mississippi River Drainage Basin

7. River Systems Three zones Sediment production Sediment transport
Sediment deposition

8. Drainage Patterns Networks of streams form distinctive patterns
Drainage pattern varies by terrain
Four common drainage patterns
Dendritic
Rectangular
Radial
Trellis

9. Drainage Patterns

10. 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)

11. 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

12. Channel Changes from Head to Mouth

13. Running Water Upstream-downstream changes Profile
Factors that increase downstream
Channel size
Factors that decrease downstream
Gradient or slope
Channel roughness

14. Longitudinal Profile of a Stream

15. Work of Running Water Erosion Transportation
Transported material is called the stream’s load
Dissolved load
Suspended load
Bed load

16. Potholes Due to Erosion

17. Work of Running Water Transportation Load is related to a stream’s
Competence – maximum particle size
Capacity – maximum load
Capacity is related to discharge

18. Work of Running Water Transportation Deposition Stream sediments
Caused by a decrease in velocity
Competence is reduced
Sediment begins to drop out
Stream sediments
Known as alluvium
Well-sorted deposits

19. Work of Running Water 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

20. Stream Channels Bedrock channels – cut into strata
Alluvial channels – loosely consolidated sediment

21. Stream Channels Meandering streams – move in sweeping bends
Braided streams – complex network of channels

22. Braided Stream

23. Shaping Stream Valleys
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

24. Base Levels

25. Shaping Stream Valleys
Valley sides are shaped by
Weathering
Overland flow
Mass wasting
Characteristics of narrow valleys
V-shaped
Downcutting toward base level
Incised meanders

26. Shaping 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

27. V-shaped Valley of the Yellowstone River

28. Erosional Floodplain Development

29. Shaping Stream Valleys
Characteristics of wide valleys
Floodplain
Features often include
Meanders
Cutoffs
Oxbow lakes

30. Meander Loop on the Colorado River

31. Floods and Flood Control
Floods are the most common geologic hazard
Causes of floods
Weather
Human interference with the stream system

32. Floods and Flood Control
Engineering efforts
Artificial levees
Flood-control dams
Channelization
Nonstructural approach through sound floodplain management

33. Mississippi River Flood of 1993

34. Groundwater: Water Beneath the Surface
Largest freshwater reservoir for humans
Geological roles
As an erosional agent, dissolving by groundwater produces
Sinkholes
Caverns
An equalizer of stream flow

35. 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

36. 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

37. Groundwater Features

38. 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

39. 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

40. Old Faithful Geyser in Yellowstone National Park

41. Groundwater Features associated with groundwater Wells Artesian 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

42. Cone of Depression Formation

43. Artesian Systems

44. Groundwater Environmental problems associated with groundwater
Treating it as a nonrenewable resource
Land subsidence caused by its withdrawal
Contamination

45. Subsidence

46. 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. 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. 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

49. Development of Karst Landscape