Geography M2 Landslide

Geography  Module #2  Unit #2  Lesson #8
BEGINBEGIN

OBJECTIVES
What are landslides?
Where do landslides
occur?
Natural factors that
cause landslides
Man-made factors
that induce landslides
QUIZ
INTRODUCTION
Impact of landslides
Mitigation Measures
Introduction
Landslides are one of the major natural hazards in
Jamaica. In this lesson you will learn about the
natural and human factors that cause landslides,
the damage landslides can cause and measures
that are used to prevent landslides.
2

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Objectives
As a result of this lesson, you will be able to
1. Describe a landslide
2. Explain the natural and human factors that cause
landslides
3. Realize that landslides are natural hazards
4. Recognize an area that has been affected by
landslide
5. Assess measures used to stabilize slopes
6. Aware of the impact of landslides on the natural
and built environment
3

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
 Landslides are a rapid type of mass movement.
 During a landslide, soil, rock or both fall suddenly
under the influence of gravity.
CHECKCHECK
In Slide Show view, type your
answer in the box below.
Click CHECK for feedback.
4

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
The material (soil/rock)
that is displaced during a
landslide, accumulates at
the base of the slope and
a scar marks the place
from which material is
removed.
Scar
Soil at
base
5

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Where do landslides occur?
Landslides occur on
steep slopes in
mountainous or hilly
areas, along the coast
and in submarine
environments(under
the sea)
CHECKCHECK
In Slide Show view, type your
answer in the box below.
Click CHECK for feedback.
6

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Natural factors that cause landslides
The force of gravity acts upon the
overhang resulting in slope failure.
The river (running water) erodes
(removes) material from the base of the
slope, thereby over steepening the slope.
The river (running water) erodes
(removes) material from the base of the
slope, thereby over steepening the slope.
Landslides occur when a steep slope is
undercut by running water.
7

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
The erosive action of
waves removes
material from the base
of a cliff resulting in the
over steepening of the
slope. The force of
gravity acts upon the
overhang causing slope
failure/landslide
8

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Landslides are caused by the lubricating action of
water. This is common where permeable rock
which allows water to collect in joints and bedding
planes overlies impermeable rock such as clay. The
water soaks through the permeable layer and
settles on top of the clay. The surface of the clay
becomes smooth and slippery over which the
permeable layer easily slides.
9

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Weathered material also called regolith allows
water to pass through. This means that it is
permeable. The permeable regolith rests on top of
an impermeable bedrock. Water collects on the
surface of the bedrock creating a slippery surface
over which the reoglith slides.
10

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Earthquakes can also trigger landslides. The
shaking that occurs during an earthquake can
cause weathered material on steep slopes to slide
down hill resulting in a landslide.
11

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Click open the link and watch the video at:
http://www.youtube.com/watch?v=Vc6ouosXk0Q&feature=related
As you watch note the following:
Speed of down slope movement
Slope angle
Bedding planes and joints
Source of lubrication
Where material rests and scar left
12

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Man-made factors that induce
landslides
13
The actions of man can
cause landslides.
In order to construct
roads or railways
material is removed from
the base of a slope.
The removal of material
from the base of the
slope weakens the slope
making it susceptible to
failure.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
landslides
The construction of buildings on slopes will add
pressure which can result in slope failure.
14

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Man-made factors that induce landslides
Changes in land use
such as clearing a
forest to facilitate the
planting of crops or
the building of
houses can reduce
the strength of a
slope and result in
slope failure.
15

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
landslides
16
Vegetation on slopes will
intercept some of the
rainfall thus preventing it
from reaching the slope.
The vegetation will also
absorb some of the moisture
therefore less is available to
lubricate the soil.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Impact of landslides on the built
environment
17
Landslides can block or cut off roads.
Roads become impassable and communities are
marooned.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Impact of landslides on the built
environment
18
Landslides can bury buildings and cause loss of life.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Impact of landslides on the natural
environment
19
Landslides remove
valuable top soil from
farmland or bury
farms; crops and
livestock under rock
and soil.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
environment
20
Landslides also add sediments to rivers, raising
channel levels and increasing the risk of flooding in
the future.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
environment
21
Landslides can block rivers thus creating a dam.
The dam may remain for a long time but when it
fails can cause flooding.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Mitigation measures
Retaining walls
Retaining walls
These must be built
with outlets for water.
If water and soil are
allowed to build up
behind the wall the
wall may not be strong
enough to withstand
the pressure and may
break.
22

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Mitigation Measures
Gabion basket
Gabion basket – rocks
are packed against the
slope and are then
secured with mesh.
The packed stones
allow for proper
drainage of the slope.
23

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
QUIZ
24
Are you ready to test yourself?
There are five multiple choice items that you are
required to do.
For each item, click on the letter of the correct
response and then click the button ‘NEXT
QUESTION’ to continue.
Click the BEGIN QUIZ button to begin.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
QUIZ: Question 1
25
The rapid movement of rock and soil down a slope
is referred to as;
A. WeatheringA. Weathering
B. RegolithB. Regolith
C. Soil creepC. Soil creep
D. LandslideD. Landslide
FEEDBACKFEEDBACK

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Quiz: Feedback to Question 1
26
The rapid movement of rock and soil down a slope
is referred to as landslides .
NEXT QUESTIONNEXT QUESTION

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
QUIZ: Question 2
27
Landslides occur in all of the following areas
EXCEPT
A. On steep slopes in hilly areaA. On steep slopes in hilly area
D. On sloping land under the seaD. On sloping land under the sea
C. Along the coastline with steep cliffsC. Along the coastline with steep cliffs
B. On gently sloping landB. On gently sloping land
FEEDBACKFEEDBACK

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
28
Landslides occur in all of the following areas
EXCEPT on gently sloping land.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
QUIZ: Question 3
29
Which of the following is a natural factor that
contributes to landslides?
A. Building gabion basketsA. Building gabion baskets
D. Cutting a road at the base of a slopeD. Cutting a road at the base of a slope
B. Construction of houses on slopesB. Construction of houses on slopes
C. Lubricating action of rain waterC. Lubricating action of rain water
FEEDBACKFEEDBACK

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
30
Question 3: Which of the following is a natural
factor that contributes to landslides?
Answer: The lubricating action of rain water

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
Quiz: Question 4
31
What human activity can trigger landslides?
A. Building retaining wallsA. Building retaining walls
D. Building roads on gently sloping landD. Building roads on gently sloping land
C. Using terraces when farming on slopesC. Using terraces when farming on slopes
B. Removing vegetation from slopesB. Removing vegetation from slopes
FEEDBACKFEEDBACK

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
32
Question 4: What human activity can trigger
landslides?
Answer: Removing vegetation from slopes.

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
QUIZ: Question 5
33
Landslides can result in all of the following EXCEPT
B. Blocking of roadsB. Blocking of roads
D. Creating dams along riversD. Creating dams along rivers
C. Burying housesC. Burying houses
A. Eruption of a volcanoA. Eruption of a volcano
FEEDBACKFEEDBACK

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
34
Landslides can result in all of the following EXCEPT
eruption of a volcano.
END OF QUIZEND OF QUIZ

OBJECTIVES
Where do landslides
occur?
cause landslides
Man-made factors
QUIZ
INTRODUCTION
Mitigation Measures
End of Quiz
35
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Geography M2 Landslide

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