Warm-Up:  How is weathering and erosion different?

Ch. 11: Flow of Freshwater

11-1: The Active River  Erosion:  Process by which soil and sediment are moved from 1 spot to another  Ex.) Grand Canyon  Six million years in the making…and still going

Rivers: Development  Rivers are complex  Built from many smaller waterways  Watershed (Drainage Basins): area of land from which a stream or river collect runoff  Ex.) Largest one in the US is the Mississippi River  Ex.) Largest in County is the Roseau River

Stream Erosion  When a stream erodes they make a channel  Usually narrow and steep  As they get large and larger they make a river  3 Factors After stream Erosion:  1.) Grade (steepness)  2.) Discharge (amount of water)  3.) Load (amount of material)  Suspended (small)  Dissolved (very small)  Bed (large)

Stage of River Development  William Morris Davis: modeled stream development  1.) Young streams: flows swiftly through a steep valley  High energy, bottom erodes fast (side not so much)  2.) Mature streams: flows more smoothly through its valley  Erodes on the sides (no bottom), river starts to curve  The river begins to meander  3.) Old streams: flows smoothly through a flood plain  Little erosion, few tributaries  Ex.) Mississippi River delta  guy.com/teaching/iac/animations/stream_processes.htm guy.com/teaching/iac/animations/stream_processes.htm

Review:  What is erosion?  What affects river erosion?  What are the different stages of rivers?

11-2: Stream and River Deposits  Deposition:  Process in which material is laid down or dropped  Rock and soil deposited by streams is called sediment  Where do you think sediment would be deposited in a river?

Deposition of water  Placer Deposits:  Where heavy minerals are deposited in rivers  Ex.) Gold—Gold Rush of 1849  Deltas: a fan shaped deposit in a lake or ocean  Made mostly of mud  A lot of diversity of plants and life (why?)

Deposition on Land  Alluvial Fans:  When a mountain stream slows down and deposits its sediment on flat land

Flooding  Flood plains:  Area around a river that forms from sediment deposited from a flood  Rich soil for farming  Floods bring new topsoil to area  Ex.) Red River Valley  However, flooding is not always beneficial

Flooding Continued…  Flooding Dangers:  Very bad for a city, town, etc.  Can kill people as well  Ex.) 1993 Mississippi flood  Flooding Prevention:  Dam:  Can redirect water or hold water back  Levee:  Build up of dirt  Helps keep water in its banks

11-3: Water Underground  Groundwater:  Water that collects in the ground and fills pores and empty spaces  2 zones that affect groundwater:  Aeration (water passes through this)  Saturation (where water collects)  Water Table: boundary of the 2 zones  Rises and falls between spring and fall

Aquifers  Aquifer:  Layer that stores groundwater  Allows water to flow underground  2 things affect the flow of groundwater  Porosity:  Open space between rock particles that holds water  Large particles will have more porosity  Permeability:  The ability to let water pass through  Larger particles are more permeable  Crushed rock vs. clay

Springs and Wells  1.) Well: man made hole deeper than water table  Can dry up seasonally  2.) Artesian Spring: free flowing water because of crack in aquifer cap  Geysers: hot spring that erupts periodically  Ex.) Old faithful

Groundwater causes Erosion?  Yes it does!  It does it in 2 ways: caves and sinkholes  1.) caves: water drips slowly removing particles and minerals leading to a caved being formed  Stalactites-ceilings  Stalagmites-floor  2.) Sinkholes: when a depression forms on the surface due to a…  Collapsed cave  Dissolved particles that get carried away

Stalactites & Stalagmites