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Lecture Outlines PowerPoint

Chapter 5

Earth Science, 12e

Tarbuck/Lutgens

Earth Science, Earth Science, 12e12e

Running Water and Running Water and GroundwaterGroundwater

Chapter 5Chapter 5

Earth as a system: the Earth as a system: the hydrologic cycle hydrologic cycle

Illustrates the circulation of Earth’s water supply

Processes involved in the cycle• Precipitation• Evaporation• Infiltration• Runoff• Transpiration

The hydrologic cycleThe hydrologic cycle

Figure 5.3

Sources of Earth’s waterSources of Earth’s water

Figure 5.2

Running water Running water

Drainage basin• Land area that contributes water to a river

system• A divide separates drainage basins

Drainage basins and Drainage basins and drainage dividesdrainage divides

Figure 5.4


Streamflow • Factors that determine velocity

• Gradient, or slope • Channel characteristics

• Shape• Size• Roughness

• Discharge – volume of water flowing in the stream (generally expressed as cubic feet per second)


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


Upstream-downstream changes • Profile

• Factors that increase downstream • Channel size

• Factors that decrease downstream• Gradient, or slope • Channel roughness

Longitudinal profile Longitudinal profile of a streamof a stream

Figure 5.7


The work of streams • Erosion• Transportation

• Transported material is called the stream’s load• Dissolved load • Suspended load• Bed load


The work of streams • Transportation

• Load is related to a stream’s • Competence – maximum particle size• Capacity – maximum load

• Capacity is related to discharge



• Deposition• Caused by a decrease in velocity• Competence is reduced • Sediment begins to drop out

• Stream sediments • Known as alluvium• Well-sorted deposits



• Features produced by deposition • Deltas – exist in ocean or lakes• Natural levees – Form parallel to the stream

channel • Area behind the levees may contain

backswamps or yazoo tributaries

Formation of natural levees Formation of natural levees by repeated floodingby repeated flooding

Figure 5.21


Base level • Lowest point to which a stream can erode • Two general types

• Ultimate – sea level• Temporary, or local

• Changing causes readjustment of the stream – deposition or erosion

Adjustment of base level Adjustment of base level to changing conditionsto changing conditions

Figure 5.15


Stream valleys • Valley sides are shaped by

• Weathering • Overland flow• Mass wasting

• Characteristics of narrow valleys • V-shaped• Downcutting toward base level


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

A narrow, V-shaped valleyA narrow, V-shaped valley

Figure 5.17 A

Continued erosion and Continued erosion and deposition widens the valleydeposition widens the valley

Figure 5.17 B

A wide stream valley is A wide stream valley is characterized by meandering on characterized by meandering on

a well-developed floodplaina well-developed floodplain

Figure 5.17 C


Stream valleys • Characteristics of wide valleys

• Floodplain • Features often include

• Meanders• Cutoffs• Oxbow lakes

Erosion and deposition along Erosion and deposition along a meandering streama meandering stream

Figure 5.10

A meander loop on the A meander loop on the Colorado River Colorado River

Figure 5.18

Formation of Formation of a cutoff and a cutoff and oxbow lakeoxbow lake

Figure 5.11


Drainage patterns• Networks of streams that form distinctive

patterns• Types of drainage patterns

• Dendritic• Radial• Rectangular• Trellis

Drainage patternsDrainage patterns

Figure 5.22


Floods and flood control • Floods are the most common geologic hazard • Causes of floods

• Weather• Human interference with the stream system


Floods and flood control • Engineering efforts

• Artificial levees• Flood-control dams• Channelization

• Nonstructural approach through sound floodplain management

Satellite view of the Missouri Satellite view of the Missouri River flowing into the River flowing into the

Mississippi River near St. LouisMississippi River near St. Louis

Figure 5.23 top

Same satellite view during Same satellite view during flooding in 1993flooding in 1993

Figure 5.23 bottom

Water beneath the Water beneath the surface (groundwater) surface (groundwater)

Largest freshwater reservoir for humans Geological roles

• As an erosional agent, dissolving by groundwater produces

• Sinkholes• Caverns

• An equalizer of streamflow


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



• 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

Features associated with Features associated with subsurface watersubsurface water

Figure 5.26



• 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


Features associated with groundwater• Springs

• Hot springs • Water is 6–9°C 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

Old Faithful geyser in Old Faithful geyser in Yellowstone National ParkYellowstone National Park

Figure 5.29


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

Formation of a cone of Formation of a cone of depression in the water tabledepression in the water table

Figure 5.31

Artesian systemsArtesian systems

Figure 5.32


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


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


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)

Cave Features in Lehman Caves, Great Cave Features in Lehman Caves, Great Basin National Park, and Carlsbad Basin National Park, and Carlsbad

Caverns National ParkCaverns National Park

Figure 5.38


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

Features of karst Features of karst topographytopography

Figure 5.39 C

End of Chapter 5End of Chapter 5

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stream deposition

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