Tarbuck & Lutgens

Stanley C. Hatfield Southwestern Illinois College

» Illustrates the circulation of Earth’s water supply » Processes involved in the cycle ˃Precipitation ˃Evaporation ˃Infiltration ˃Runoff ˃Transpiration

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

» 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

» 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

» Upstream-downstream changes ˃Profile +Factors that increase downstream – Channel size +Factors that decrease downstream – Gradient, or slope – Channel roughness

» The work of streams ˃Erosion ˃Transportation +Transported material is called the stream’s load – Dissolved Particle – Suspended Particle – Bed Particle

» The work of streams ˃Transportation +Load is related to a stream’s – Competence – maximum particle size – Capacity – maximum load – Capacity is related to discharge » Greater the discharge the greater the capacity.

» 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

» 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

» 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

» 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

» Stream valleys ˃Characteristics of wide valleys +Floodplain +Features often include – Meanders – Cutoffs – Oxbow lakes

» Drainage patterns ˃Networks of streams that from distinctive patterns ˃Types of drainage patterns +Dendritic +Radial +Rectangular +Trellis

» 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

» Largest freshwater reservoir for humans » Geological roles ˃As an erosional agent, dissolving by groundwater produces +Sinkholes +Caverns ˃An equalizer of stream flow

» 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

» 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

» 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

» 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

» 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

» 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)

» 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