Earth Science, 13e Tarbuck & Lutgens

Running Water and Groundwater Earth Science, 13e Chapter 5 Stanley C. Hatfield Southwestern Illinois College

Chapter 5 Opener

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

The hydrologic cycle

Running water Drainage basin Land area that contributes water to a river system A divide separates drainage basins

Drainage basins and divides

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) Discharge = Depth x Width x Velocity

Running water Upstream-downstream changes Profile Cross-sectional view of a stream From headwaters (source) to mouth Profile is a smooth curve Gradient decreases from the headwaters to the mouth Factors that increase downstream Velocity Discharge Channel Size

Running water Upstream-downstream changes Profile Factors that decrease downstream Gradient, or slope Channel roughness

Longitudinal profile of a stream

FIGURE 5.11

Running water The work of streams Erosion Transportation Transported material is called the stream’s load Dissolved Load – minerals (oxygen, salts, nitrogen carbon dioxide) Discussed in ppm (parts per million) Velocity has little to no effect on Suspended Load - silt/clay Usually the largest load of a stream Settling velocity Bed Load –move material via saltation Discuss the location and movement of this material

Running water The work of streams Transportation Load is related to a stream’s Competence – maximum particle size Capacity – maximum load Capacity and Competence are related to discharge Greater the discharge the greater the capacity competence Gradient Examples – Low  Mississippi Delta High  Colorado River going through the grand canyon (drops 10ft/mi) Stream capacity is a measure of the total sediment (material other than water) a stream can carry Competence is a measure of the streams ability to move sediment

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

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

Running water 5.6 Base level Two general types Point at which a stream deposits into a larger body of water that is usually lentic or lotic. Lentic  standing water Lotic  Running water Estuaries are the more common end point. Two general types Ultimate – sea level Erosion and transport processes becomes weaker and depositional process takes over. Temporary – Local Includes lakes, resistant layers of rock, and point at which tributaries enter a larger stream What happens to the velocity of a stream as it enters a lake? Changing causes readjustment of the stream – depositional or erosional processes will change.

Adjustment of base level to changing conditions

Running water Stream valleys Types of Stream Valleys Narrow, Steep, Wide Consists of the channel and the surrounding terrain of that contributes water to the stream. Most stream valleys are wider at the top than the bottom. Is the stream the only agent working on the stream valley? Valley sides are shaped by Weathering Work of wind and water on the surface Overland flow Runoff Mass wasting Large and sudden movements of land mass

Running water Characteristics of narrow valleys V-shaped Created by the hydraulic powers if the stream moving bed load across the bed of the channel in turbulent water. Down cutting toward base level is the dominant activity Features often include: Rapids –result of resistant rock acting as a temporary base level Down cutting continues downstream Waterfalls – Places where the stream makes an abrupt drop Both are a result of a variation in erodability of the bedrock Highest water fall in the world is Angel Falls

V-shaped valley of the Yellowstone River

Running Water Characteristics of wide valleys Stream is near base level Downward erosion is less dominant Stream energy is directed from side to side Floodplains http://www.youtube.com/watch?v=qEz4MiOVTMM Over time floodplains will widen Mississippi River has areas w/ 100mi between divides Features often include Meanders Incised Meanders – Found in steep narrow valleys Created by a shifting in base level. Cutoffs  plays a major part in the shifting of deltas Oxbow lakes

Continued erosion and deposition widens the valley

Characteristics of a wide stream valley

A meander loop on the Colorado River

5.8 Depositional Landforms Streams can create depositional features through out the course of the stream. Small-scale/short-term features Deposits are referred to as bars Often consist of both medium and fine grained material. Temporary feature of the stream channel Relocated as streams transport material toward the ocean. Large-scale/long-term features Deltas, natural levees and alluvial fans All of the features are found most often where flow velocity has ______. decreased

Depositional Landforms Deltas Formed where streams enter a lentic body of water Ex. Lakes, in-land sea, or ocean Depositional processes take over at this point and start to convert the main stream into distributaries Distributaries take water away from the main stream. Natural Levees Form where streams have overflowed their banks Once the stream leaves it’s channel the velocity decreases quickly resulting in the deposition of sediment. Over time the consistent flooding may result in the large levees Levees of the Mississippi can reach up to 20ft (6m) Areas behind levees tend to drain poorly and are often result in Yazoo tributaries and back swamps Alluvial Fans Result of streams w/ high flow velocity entering a broad flat plain

Formation of natural levees by repeated flooding

Running water 5.9 Drainage patterns Networks of streams that form distinctive patterns Types of drainage patterns Dendritic- the most common type of drainage pattern Schuylkill river and Delaware Characterized by its tree-like branching Underlying geology is generally uniform and resistant to erosional processes Radial – spokes on a wheel Affiliated w/ volcanoes Rectangular- forms as a result of crisscrossing of joints and/or faulting Characterized by 90degree angles Trellis - rectangular pattern in which tributaries are parallel to each other

Drainage patterns

Running water Floods and flood control Floods are the most common geologic hazard Causes of floods Weather Human interference with the stream system Flood Videos NASA Mississippi Flooding 2011 http://www.youtube.com/watch?v=5ju1boh5bq8 Mississippi Flooding June 2012 http://www.youtube.com/watch?v=QQH4IlSvlu0

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

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

Same satellite view during flooding in 1993

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

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

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

Features associated with subsurface water

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

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

Old Faithful geyser in Yellowstone National Park

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

Formation of a cone of depression in the water table

Artesian systems

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

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

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)

Cave features in Carlsbad Caverns National Park

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

Features of karst topography

End of Chapter 5