Mass movements is the term used to define the different ways that weathered material can alter the s

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These slide-shows are all on the Prepwork folder
if you wish to copy any notes from them we will
not be stopping in class for you to do this
Mass movements is the term used to define the
different ways that weathered material can alter
the scenery.
The two forces acting on the material are-
Friction, which stops them sliding downhill too
fast.
Gravity, which pulls the particles down.
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There are four main factors that influence mass
movements-

• How much water is involved in the action.
• How much of an angle is needed on the slope.
• How quickly the movement happens.
• The amount of vegetation cover is also important
  in some types of movement.

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ROCKFALLS- read from the booklet, factzone
2a). Answer the questions that follow, in
sentences in your jotter. Answers are suggested
on the following slides for you to check and
amend your answers.
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1. What angles are rockfalls most likely to
happen at?
2. Which secondary processes are very important
too?
1. The best angle is between 70 and 90 degrees
from horizontal.
2. Freeze-thaw and frost-shattering are important
processes.
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3. So what condition ought the rock face to be in
if a rockfall is to happen?
4. What angle does scree usually initially settle
at?
3. The face should be well- jointed or cracked
for rockfalls to happen.
4. Scree settles between 34 and 40 degrees,
usually.
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5. Explain what is meant by size- sorting and
why it happens.
5. Particles travel down the slope depending on
their weight and density. Lighter ones finish
nearer to the face, heavier ones travel further,
often moved by rolling over smaller ones.
6. What is the usual angle of an inactive scree
slope?
6. The inactive slope consolidates at 37 degrees
where it usually grasses over.
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Climbers call these types of screes stone
chutes.
Their technical name is talus slope.
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A rockfall and talus slope in Arizona
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SLIDES/SLUMPS- read from the booklet,factzone
2b). Answer the questions that follow, in
sentences in your jotter. Answers are suggested
on the following slides for you to check and
amend your answers.
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1.What two roles does heavy rainfall play?
1. It lubricates the slip plane and makes the
material heavier and likely to move.
2. What is the difference in the motion of the
material in slumps and slides?
2. Slumped ground has rotated whereas slides
travel down in a straight line.
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The Quiraing in Skye shows spectacular rotational
slumping.
Spot the tourists?
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MUDFLOWS- read from the booklet,factzone 2c).
Answer the questions that follow, in sentences
in your jotter. Answers are suggested on the
following slides for you to check and amend your
answers.
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1. How gentle a slope can mudflows start on?
1. They can start on a slope as gentle as 5 or 6
degrees. Angles over 10 degrees are more common.
2. What shape does the material stop in?
3.How do you describe the speed of a mudflow?
3. Mudflows happen very quickly indeed!
2. The material stops in a lobe/fan shape.
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This mudflow happened several years before the
photo was taken- the scars are still very visible!
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A mudflow in Central America, October 2005
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SOIL CREEP- read from the booklet,factzone 2d).
Answer the questions that follow, in sentences
in your jotter. Answers are suggested on the
following slides for you to check and amend your
answers.
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1.What angle of slope does this require?
1. Angles over 6 degrees are susceptable.
2.Describe how biological activity may enhance
the activity.
3. Describe what terracettes look like.
3. Terracettes are small-scale ridges parallel to
the slope.
2. Plant roots and burrowing animals help the
soil to move.
4.Describe four results of soil creep.
6. See the next slide for the answer.
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6. a). Fence and telegraph posts lean down-slope
as their supports are undermined by the creep. (
note these are the same effect) b). Soil piles up
behind walls, creating deeper pockets, pushing
walls over in time. ( note there are two effects
here!) c). Roads may crack open parallel to the
slope angle, and will need frequent repair. d).
Terracettes spoil the smooth surface of fields,
and affect land use.
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Terracettes can be seen to the right of the river
valley.
END