*Running water is the Earth’s main agent of natural erosion

Lesson 9: Energy in a stream B C Youthful Stream Middle- Age Stream Old-Age Stream

What shapes streams? Weathering: chemical and physical breakdown of sediments. Erosion: removal and transport of sediment by natural agents. Deposition: release of sediments from an erosional system (AKA Sedimentation)

Low Kinetic & Potential Energy Stream Side View Greatest Potential Energy = Stored Energy Greatest Kinetic Energy = Energy of Motion Lake Ocean Most Erosion Low Kinetic & Potential Energy Most Deposition Kinetic energy= energy in motion Potential energy= energy that is stored

Changing Stream Velocity: A. Slope increases, velocity increases B. Volume (Discharge) of water increases, velocity increases Velocity determines size of sediments ESRT pg 6

River Landscapes in America Yuba river, Nevada

How sediments move - Flow of the River River Floor Cobbles & Pebbles Move by sliding, rolling Slower than the water Silt, Clay & Dissolved Ions Moves in suspension Same speed as water Sand Moves by Bouncing Slower than water River Floor

Different size particles Well Sorted Same particles size Unsorted Different size particles

Stream deposits are well sorted (same size) Example: “Delta” Forms when a river carrying sediment reaches a body of water. The river water spreads out, velocity slows and deposits sediments.

Clear water suspension suspension Area of vegetation

Amazon Delta

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Q7: State the maximum size particle (cm) that can Use Particle Size versus Stream Velocity Graph on “Baby” page 6 Q7: State the maximum size particle (cm) that can be transported in a 1cm/sec moving stream. Q8: What is the maximum stream velocity needed to transport a 2.0 cm size particle?

Life Cycle of a Stream

Youthful Characteristics Middle Age Characteristics Old Age Characteristics

Youthful Stream Lake (Source of Water) Waterfall Steep Slope Rapid Flow Rapids

V-shaped valleys

Middle Age Velocity decreases due to decrease in slope Begins to meander Downcutting slows due to velocity decrease Valley walls become wider

Old Age Stream Slow speed Almost flat slope Very broad, flat valley (flood plain) filled with fine sediments - alluvium Very little erosion Oxbow lake Wide meanders Wide flood plain

Oxbow lake – a meander becomes so great, it cuts off forming a lake.

Rejuvenation – a stream may be brought back to a youthful stage of development at any time by …… (ex. Grand Canyon)

Uplift of land; create a steeper gradient. Resulting in.. Higher stream flow and more downcutting of valley 2. Stream takes on more discharge by tributaries resulting in more downcutting.

Name the part of the stream’s life cycle in the picture