LANDSLIDES!

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LANDSLIDES!
failure surface
Melissa Beukeboom _at_
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What is a landslide?
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Tug of War
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When a landslide occurs.
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WHY?
What helps gravity to win?
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1. Type of sediment
2. Erosion
3. Water content in soil
4. Disturbances like

• Earthquakes
• Volcanic eruptions
• Machinery, traffic, mining

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SOIL
Lets take a closer look!
1. Type of Rock Particles (a.k.a. Sediment)
ROCK PARTICLES a.k.a. SEDIMENTS
WATER
AIR
ORGANIC MATTER
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ROCK PARTICLES

• Rocks are weathered (broken down) by water,
  wind, and ice into smaller and smaller pieces
  called

SEDIMENTS

• Main types of SEDIMENTS
• gravel
• sand
• silt
• clay

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1. Type of Rock Particles (a.k.a. Sediment)
Gravel and sand grains are very angular in shape.
Their sharp edges hold on to each other,
increasing FRICTION and fighting GRAVITY.
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What happens to these sediments when a landslide
occurs?
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1. Type of sediment (continued)

• Clay particles are flat and fit together very
  tightly.
• This prevents water from moving between clay
  particles easily.
• Water pressure can build up in slopes made of
  clay.

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1. Type of sediment (continued)
A SPECIAL CASE!!
QUICK CLAYS
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Do we have quick clays in Ontario?
YES!
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Cardhouse Structure
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1. Type of sediment (continued)

• The card house structure makes quick clay very
  stable.

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2. Erosion

• When a slope is over-steepened, it becomes
  unstable
• Rivers erode the base of slopes and make them
  too steepmaking it unstable

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3. Water Content

• Too much water added to soil, pushes the
  sediment particles apart.
• The particles lose contact with each
  othertherefore they lose FRICTION!

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4. Disturbances

• Disturbances also push particles apart, causing
  them to lose contact with each other
• They lose FRICTION, so.

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4. Disturbances include
Volcanoes!
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4. Disturbances include
Volcanoes!
Earthquakes!
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4. Disturbances include
Earthquakes!
Volcanoes!
Construction
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4. Disturbances include
Earthquakes!
Volcanoes!
Construction
Heavy Traffic
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4. Disturbances include
Earthquakes!
Volcanoes!
Construction
Deforestation
Heavy Traffic
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Lets re-cap
Landslides occur when the land is
unstableallowing
Instability depends on

• The type of sediment
• Water content in the soil
• Erosion over-steepening the slope
• A major disturbance

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When a landslide occurs

• It can be fast

or slow

• It can look like the wave or falling dominos

To concludehere is a bit humour

• The domino effect

Imagine the people are sediment particles
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Its time to slip, slide and away
The End!