tgaw, lesson 4, ox bow
Post on 27-Mar-2016
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LESSON OUTCOMES:
W hat: Understand the main processes that cause a river to meander
How: By stimulating a physical model to explain how erosion and deposition effect the shape of a rivers course.
Why: So I can create an annotated diagram of key features in the middle course of a river
http://www.bbc.co.uk/northernireland/f
orteachers/water/river/ft_cl_water_
river_journey.shtml
• Watch the 2 video
clips about the
features found in the
middle course of
river.
• Come up with 3
ways that the middle
course is different to
the upper course.
ACTIVATE: HOW DOES THE RIVERS JOURNEY CHANGE AS
IT MOVES FROM THE UPPER TO MIDDLE COURSE?
Meander neck becomes
smaller
new course of
the river
oxbow lake
When the river
floods it breaks
through the thin
meander neck and
the river takes the
easier, straight
course. This leaves
the meander loop
‘cut off’ as an oxbow
lake. Over time, the
oxbow lake will
become colonised
by vegetation.
Oxbow lakes
DEMONSTRATE: HOW IS DEPOSITION AND
EROSION RESPONSIBLE FOR THE SHAPE OF A
MEANDER? Task 1:
Create virtual meander in class room to show how the rivers energy
changes.
http://www.bbc.co.uk/schools/gcsebitesize/geography/riverswater/river_
landformsrev2.shtml
Task 2:
a. Draw diagram D pg.105 to demonstrate how a river meanders.
b. Annotate your diagram by adding the number code of key terms and
definitions into the appropriate places.
Task 3:
a. Complete the diagram on your worksheet to show how ox bow lakes
form.
b. Fill in the missing words to show that you can explain the processes
that cause an ox bow lake to form.
REFLECT: SELF ASSESS YOUR PROGRESS
TODAY!
1. As the outer banks of a meander continue to be eroded through processes such as
hydraulic action the neck of the meander becomes narrow and narrower.
2. Eventually due to the narrowing of the neck, the two outer bends meet and the river
cuts through the neck of the meander. The water now takes its shortest route rather
than flowing around the bend.
3. Deposition gradually seals off the old meander bend forming a new straighter river
channel.
4. Due to deposition the old meander bend is left isolated from the main channel as an
ox-bow lake.
5. Over time this feature may fill up with sediment and may gradually dry up (except for
periods of heavy rain). When the water dries up, the feature left behind is known as a
meander scar
I got …./10
Understanding of meanders …../5 Understanding of ox bow lakes …./5
Enjoyed learning …../5 Any other comments: ………
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