Topic: Erosion & Running Water

* Earth’s main agent of natural erosion

What is erosion?

• Erosion is -

Agents of Erosion

• Agents of erosion include --• Running water is the big Kahuna of all

erosional agents.

How does water carry the sediments?

• Water carries sediments in the following ways:–Solution – -–Suspension – -–Rolling or bouncing along the streambed.–Floating – -

River Floor

Flow of the River

Cobbles & PebblesMove by sliding, rolling along the river floorSlower than the water flow

SandBounces along river floorSlower than the water flow

Colloids (Silt & Clay) & Dissolved IonsCarried in suspensionSame speed as water

Streams act as conveyor belts

Lake

Ocean

Stream Side ViewGreatest Potential Energy = Stored Energy

Greatest Kinetic Energy = Energy of Motion

Low Kinetic & Potential Energy

Most Erosion

Most Deposition

Dynamic EquilibriumRate of Erosion = -

Changing Stream Velocity:

• A. --• B. --

Stream velocity determines size of sediment carried.

ESRT pg 6 Take out your ESRT!

Streambed--

--

Stream bank

Stream bank

Region of maximum stream velocity changes when streams bend or turn.

Stream

Region of maximum velocity shifts to --

Region of minimum velocity shifts to --

Since the region of maximum stream velocity is at the outside of the curves, streambeds are more eroded at the outside of curves.

Stream

A

A’

B

B’

C’C

AA’Streambed

B’ B

StreambedC C’Stream

bed

What does erosion by rivers create?

• Abraded sediments– --

FQ

The stream’s velocity is 100 cm/sec, what size sediment(s) can the stream transport?

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Topic: Life Cycle of a Stream

Youthful Stream

Steep Slope Rapid

Flow

Lake

(Source of Water)

Rapids

Waterfall

This forms V-shaped valleys.

** ---**

Middle AgeVelocity decreases

due to decrease in slope

Downcutting slows due to velocity decrease

Valley walls become wider

Begins to meander

Old Age Stream Slow speed

Almost flat slope

Very little erosion

Wide meanders

Oxbow lake

Wide flood plain

Very broad, flat valley (flood plain) filled with fine sediments - alluvium

Meander – --

Oxbow lake – --

Rejuvenation – a stream may be brought back to a youthful stage of development at any time by uplifting the land.

(ex. Grand Canyon)

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

picture

FQ:What shape do stream valleys make?

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