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

IntroductionLandslides 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.

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QUIZ

INTRODUCTION


Mitigation Measures

ObjectivesAs a result of this lesson, you will be able to 1. Describe a landslide 2. Explain the natural and human factors that cause

landslides3. Realize that landslides are natural hazards4. Recognize an area that has been affected by

landslide5. Assess measures used to stabilize slopes6. Aware of the impact of landslides on the natural

and built environment

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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.

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INTRODUCTION


Mitigation Measures

What are landslides?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

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Mitigation Measures


Landslides occur on steep slopes in mountainous or hilly areas, along the coast and in submarine environments(under the sea)

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QUIZ

INTRODUCTION


Mitigation Measures


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.

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QUIZ

INTRODUCTION


Mitigation Measures

Natural factors that cause landslides 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

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INTRODUCTION


Mitigation Measures

Natural factors that cause landslides 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.

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Mitigation Measures

Natural factors that cause landslides 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.

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INTRODUCTION


Mitigation Measures

Natural factors that cause landslides 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.

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INTRODUCTION


Mitigation Measures

Natural factors that cause landslidesClick 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 angleBedding planes and jointsSource of lubrication Where material rests and scar left

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QUIZ

INTRODUCTION


Mitigation Measures


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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.

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INTRODUCTION


Mitigation Measures


The construction of buildings on slopes will add pressure which can result in slope failure.

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QUIZ

INTRODUCTION


Mitigation Measures


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.

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QUIZ

INTRODUCTION


Mitigation Measures


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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.

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INTRODUCTION


Mitigation Measures

Impact of landslides on the built environment

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Landslides can block or cut off roads. Roads become impassable and communities are marooned.

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INTRODUCTION


Mitigation Measures

Impact of landslides on the built environment

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Landslides can bury buildings and cause loss of life.

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INTRODUCTION


Mitigation Measures

Impact of landslides on the natural environment

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Landslides remove valuable top soil from farmland or bury farms; crops and livestock under rock and soil.

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INTRODUCTION


Mitigation Measures


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Landslides also add sediments to rivers, raising channel levels and increasing the risk of flooding in the future.

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Mitigation Measures


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Landslides can block rivers thus creating a dam. The dam may remain for a long time but when it fails can cause flooding.

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Mitigation Measures

Mitigation measures Retaining wallsRetaining wallsThese 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.

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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.

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INTRODUCTION


Mitigation Measures

QUIZ

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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.

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QUIZ

INTRODUCTION


Mitigation Measures

QUIZ: Question 1

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The rapid movement of rock and soil down a slope is referred to as;

A. Weathering A. Weathering

B. Regolith B. Regolith

C. Soil creep C. Soil creep

D. Landslide D. Landslide

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INTRODUCTION


Mitigation Measures

Quiz: Feedback to Question 1

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The rapid movement of rock and soil down a slope is referred to as landslides .

NEXT NEXT QUESTIONQUESTION

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INTRODUCTION


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QUIZ: Question 2

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Landslides occur in all of the following areas EXCEPT

A. On steep slopes in hilly area A. On steep slopes in hilly area

D. On sloping land under the sea D. 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

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Mitigation Measures


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Landslides occur in all of the following areas EXCEPT on gently sloping land.


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QUIZ: Question 3

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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

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INTRODUCTION


Mitigation Measures


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Question 3: Which of the following is a natural factor that contributes to landslides?

Answer: The lubricating action of rain water


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INTRODUCTION


Mitigation Measures

Quiz: Question 4

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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

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INTRODUCTION


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Question 4: What human activity can trigger landslides?

Answer: Removing vegetation from slopes.


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INTRODUCTION


Mitigation Measures

QUIZ: Question 5

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Landslides can result in all of the following EXCEPT

B. Blocking of roads B. Blocking of roads

D. Creating dams along rivers D. Creating dams along rivers

C. Burying houses C. Burying houses

A. Eruption of a volcanoA. Eruption of a volcano

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INTRODUCTION


Mitigation Measures


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Landslides can result in all of the following EXCEPT eruption of a volcano.

END OF QUIZ END OF QUIZ

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QUIZ

INTRODUCTION


Mitigation Measures

End of Quiz

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geography m2 landslide

Education

damage landslides

landslides manmade factors

human factors

major natural hazards

slope failure

material soilrock

steep slopes

scar soil