Landslides: Types and Causes

Summary

This educational video delves into the hazards of landslides, a recurring phenomenon exacerbated by factors like topography, rainfall, and human activities. It highlights the significant impact on agriculture, infrastructure, and human life, with an annual cost of nearly 2 billion rupees. The script explains the different types of landslides, including falls, topples, slides, and spreads, and discusses the causes, such as slope failure, deforestation, and unscientific development, emphasizing the critical role of human interference in destabilizing slopes.

Takeaways

• 🏔 Landslides are a serious geological hazard, particularly in areas with rugged topography and heavy rainfall.
• 🌧 Landslides are a chronic problem in hilly regions due to factors like development activities and exploitation of natural resources.
• 📈 The monsoon season is a peak time for landslides, causing disruptions in communication, property loss, and sometimes loss of life.
• 🗺 The landslide hazard map of India shows high risk in the Himalayan terrain and northeastern hill ranges, with moderate risk in the western ghats.
• 💔 Landslides have a significant impact on agriculture, forests, infrastructure, and can lead to substantial monetary losses for the nation.
• 🚨 Early warning signs of landslides include tilted structures, cracks in foundations, and changes in water flow or falling debris.
• 📚 Landslides involve the downward and outward movement of soil or rock mass due to gravity and can be categorized into different types like falls, topples, slides, and spreads.
• 🔍 Key terms in landslide studies include crown, flanks, head, foot, main scarp, and surface of rupture, which help in understanding the mechanics of landslides.
• 📉 The types of landslides range from rock falls and debris slides to complex landslides that involve a combination of different movements.
• 🌳 Causes of landslides include slope failure, deforestation, hydrostatic pressure, earthquakes, intense rainfall, and human activities such as construction and land use changes.
• ⚠️ Human interference, such as improper construction practices and deforestation, significantly contributes to the instability of slopes and the occurrence of landslides.

Q & A

What is a landslide?

A landslide is a serious geological hazard involving the downward and outward movement of soil or rock mass under the influence of gravity, often triggered by factors such as heavy rainfall, slope failure, or human activities.

Why are landslides particularly common during the monsoon season?

Landslides are particularly common during the monsoon season due to heavy and prolonged rainfall, which increases the water content in the soil, reducing its stability and leading to slope failure.

What are the areas in India most prone to landslides according to the landslide hazard map?

According to the landslide hazard map, the Himalayan terrain, northeastern hill ranges, and western ghats are the areas most prone to landslides in India.

What are the socioeconomic impacts of landslides?

Landslides can cause substantial damage to agriculture, forests, roads, and telecommunication infrastructure. They can also result in injury, loss of life, and property damage, leading to significant monetary losses for the nation.

What are some early warning signs of a potential landslide?

Early warning signs of a potential landslide include tilted telephone poles or trees, cracks in foundations or roads, and sudden changes in the flow of water or falling of stones from hill slopes.

What types of landslides are mentioned in the script?

The script mentions several types of landslides, including rock fall, debris fall, soil fall, rock topple, debris topple, soil topple, rotational slides, translational slides, and complex landslides.

How do rotational slides differ from translational slides?

Rotational slides involve movement on a circular or near-circular surface of failure and are characterized by a scarp at the head. Translational slides, on the other hand, are non-rotational and involve mass movement on more or less planar surfaces.

What is the role of human activities in causing landslides?

Human activities such as deforestation, unscientific construction practices, and developmental projects like road building can destabilize slopes and contribute to landslides by altering the natural landscape and increasing the load on hill slopes.

How do earthquakes contribute to landslides?

Earthquakes can contribute to landslides by reducing the shearing resistance along fracture zones or joint planes, making loose and unconsolidated sediments on steep slopes more vulnerable to movement.

What is the significance of the surface of rupture in understanding landslides?

The surface of rupture is significant in understanding landslides as it represents the plane along which the soil or rock mass moves. Identifying this surface helps in assessing the type and potential movement of a landslide.

Outlines

00:00

🌧️ Landslides: Causes and Impacts

The first paragraph introduces the topic of landslides, highlighting them as a serious and recurring natural hazard. It mentions the primary causes such as rugged topography, heavy rainfall, and human activities like development and exploitation of natural resources. The paragraph also discusses the specific regions in India where landslides are common and the severe impacts they have on agriculture, infrastructure, human life, and the environment. The annual monetary loss due to landslides is noted to be nearly 2 billion rupees, emphasizing the socioeconomic and human misery caused by these events.

05:02

🏔️ Understanding Landslide Terminology and Types

This paragraph delves into the technical aspects of landslides, explaining the terminology used to describe different parts of a landslide, such as the crown, flanks, head, toe, and main body. It then categorizes landslides into types based on their movement and characteristics, including falls, topples, slides, and flows. Each type is further described with its specific features and examples, providing a comprehensive understanding of the various forms landslides can take.

10:03

🪨 Causes of Landslides: Natural and Anthropogenic Factors

The third paragraph focuses on the causes of landslides, which range from natural factors like slope failure and intense rainfall to human activities such as deforestation and unscientific construction practices. It explains how steep slopes, high rainfall, and poor land use changes can increase the likelihood of landslides. The paragraph also touches on the role of hydrostatic pressure, erosion, and earthquake shocks in triggering landslides, and how human interference, such as the use of explosives and improper construction, can exacerbate the problem.

15:04

🛠️ Human Activities and Their Contribution to Landslide Instability

The final paragraph emphasizes the significant role of human activities in causing landslides. It discusses how developmental and engineering activities, such as construction and hill cutting, can destabilize slopes and lead to landslides. The paragraph also mentions the consequences of overloading slopes, improper water management, and the lack of engineering considerations in construction projects. It concludes by reiterating the importance of understanding landslides and their causes, particularly the impact of human interference.

Keywords

💡Landslide

A landslide is a geological phenomenon where masses of rock, earth, or debris move downslope under the influence of gravity. It is a significant theme in the video, as it discusses the various types, causes, and impacts of landslides. The script describes how landslides can be triggered by factors such as heavy rainfall, deforestation, and human activities, and how they can cause substantial damage to infrastructure, the environment, and human life.

💡Topography

Topography refers to the physical and structural features of the landscape. In the context of the video, rugged topography is highlighted as a primary factor contributing to the occurrence of landslides, as it can lead to unstable slopes prone to such geological events.

💡Monsoon

The monsoon is a seasonal wind pattern that brings heavy rainfall to certain regions. The video mentions that landslides are particularly common during the monsoon season, affecting communication, causing loss of property, and sometimes even leading to the loss of human life.

💡Natural Resources Exploitation

This term refers to the extraction and use of natural resources such as minerals, forests, and water. The script points out that exploitation of natural resources in hilly regions can exacerbate the problem of landslides by altering the landscape and making slopes more susceptible to failure.

💡Landslide Hazard Map

A landslide hazard map is a tool used to depict areas that are at risk of experiencing landslides. The video script discusses the landslide hazard map of India, noting that the Himalayan terrain has a very high risk, while the northeastern hill ranges and western ghats are also significantly affected.

💡Ecosystem

An ecosystem encompasses all the living organisms and their physical environment in a particular area. The video explains that landslides can disturb ecosystems by damaging natural resources and the habitats of various species.

💡Socioeconomic Structure

Socioeconomic structure refers to the arrangement and relationship of social classes and economic systems within a society. The script mentions that landslides have a serious impact on the socioeconomic structure of regions, causing not only physical destruction but also economic hardship.

💡Surface Rupture

In the context of landslides, a surface rupture is the visible break or crack in the ground that forms as a result of the movement of soil or rock. The video script describes various parts of a landslide, including the main scarp, which is a steep surface on the undisturbed ground at the upper edge of a landslide, caused by the movement of displaced material.

💡Deforestation

Deforestation is the removal of trees and forests, which can have significant environmental impacts. The video script identifies deforestation as a contributing factor to landslides, as it can lead to soil erosion and destabilize slopes.

💡Hydrostatic Pressure

Hydrostatic pressure is the pressure exerted by a fluid at rest due to the force of gravity. The script explains that intense rainfall can lead to an increase in hydrostatic pressure within sediments, which can weaken them and trigger landslides.

💡Development and Engineering Activities

This term encompasses human activities related to construction and infrastructure development. The video script points out that such activities, if not conducted properly, can contribute to landslides by altering the stability of slopes and increasing the risk of slope failure.

Highlights

Landslides are a serious geological hazard with annual and recurring occurrences.

Landslides are primarily caused by rugged topography, unfavorable hill slopes, heavy rainfall, and exploitation of natural resources.

The monsoon season particularly exacerbates landslide occurrences, impacting communication and causing loss of life and property.

The landslide hazard map of India shows varying degrees of risk across different regions.

Landslides cause substantial damage to agriculture, forests, roads, telecommunication, and engineering structures.

The economic impact of landslides in India is significant, with an estimated annual loss of nearly 2 billion rupees.

Landslides not only disrupt the socioeconomic structure of regions but also cause human misery.

Landslides are categorized into different types such as falls, topples, slides, spreads, and flows.

The movement of landslides can range from soil creep to huge landslides, with varying terminologies used to describe them.

Translational slides are non-rotational block slides involving mass movement on planar surfaces.

Spread landslides are caused by liquefaction where saturated sediments transform into a liquid state.

Flow landslides involve rapid movement of material as a viscous mass, such as debris flows or mud flows.

Complex landslides involve a combination of different types of movements.

Causes of landslides include slope failure, deforestation, hydrostatic pressure, earthquakes, and development activities.

Human interference, such as construction and land use changes, significantly contributes to landslide occurrences.

The importance of understanding landslide terminologies and types for effective disaster management.

The role of early warning signs like tilted poles, cracks in foundations, and changes in water flow for predicting landslides.

Transcripts

so

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dear learners welcome

today we'll discuss about the landslides

stripes and causes

landslide is a serious jollical hazard

it's an annual and recurring phenomena

it is a major chronic problem primarily

because

of the rugged topography

unfavorable hill slopes

heavy and prolonged rainfall

development activities and exploitation

of natural resources in the hilly region

have further aggravated this problem

it is particularly common during the

monsoon affecting communication

loss of property

and sometimes even the human life

it also damages natural resources and

disturb the ecosystem and involvement

well let's see the

landslide hazard map of india

it shows that in the himalayan terrain

it is very high

and it is high in the northeastern hill

ranges

and

moderate in the western ghat and il

greece severity it comes down from the

himalayan terrain from the northeastern

religion then western heart nil greece

and eastern ghat and the vindhyan we all

know about the effect of the landslide

it causes substantial damage to

agriculture and forest wealth

roads telecommunication and major

engineering structures it has great

impact on injury and loss of life and

damage to the properties it also causes

blocking of the rivers channels thereby

forming a huge lakes which when burst

creates flash flood causing much heavy

losses

the nation suffers heavy monetary loss

every year because of the landslides

it is enormous when cumulative figures

are taken

you will be surprised that total

estimate cost for loss of property is

nearly 2 billion

rupees per annum in this landslide

incidences

thus this landslide hazards

have very serious impact not only on

socioeconomic structure of the region

but also in disruption

a complete misery to the human life

you see

any landslide is not a disaster

landscape basically the hazard

but when this landslide affect any loss

property

or the life then it becomes a disaster

let's see the effect and sign of the

landslides

well

tilted telephone poles

retaining walls or sometimes trees you

see it takes a turn near the slope

cracks in the foundation can be seen

even in the houses you can the side

walls and the driveways of the houses

even the cracks are developed on the

ground and the roads

and sudden emergence or stoppage of

flowing water

or falling of stones or boulders from

the hill slopes are also the early

warning of a landslide

now let's understand the landslide in

fact landslides are downward and outward

moment

of soil or rock mass

that may be set off by one or more

causes under the influence of gravity

whereas people have used different terms

for landslides

such as mass wasting

mass movement

slope failure and slope movement

mass movements can range in magnitude

from soil creep to huge landslides now

there are very terminologies that we use

in case of landslides

let's see crown

the top portion of a landslide is a

crown then flanks both sides that refers

to the portion of the slides with un

displaced material

adjacent to the sides of the rupture

surface

that head of the slide is the upper part

of the landslide along the contact

between the displaced material and the

main scarp and foot is the portion of

the landslide that has moved beyond the

toe of the surface of rupture that

overlap the original ground surface and

main body is the main part of the

displaced material

of the landslide that overlaps the

surface of rupture between the main scar

and toe of the surface of rupture main

scarp is a steep surface on the

undisturbed ground of the upper edge of

the landslide which is caused by the

movement of

displaced material away from the

undisturbed ground

it is visible part of the surface of the

rupture

a minus curve is a steep slope on

displaced material which is produced by

the differential movement within the

displaced material

surface absorption surface that forms

lower boundary that displace the

material below the original ground

surface is the surface of rupture and

this is very important to study

or to know what is the surface of

rupture then accumulation it is a volume

of the displaced material which has

fallen from the top and has been

accumulated on the ground surface well

so toe is the lowest usually curved

margin of the displaced material of a

landslide it is the most distinct part

from the main scarp now let let's see

the types of landslide the first

category is the false

it refers to the abrupt movement of the

slope material that becomes detached

from steep slope or cliffs

most of the movement occur by free fall

or by rolling or bouncing

depending upon the type of slope

material it may be called as rock fall

debris fall or soil fall

you see when we talk about rock fall it

is a mass of the rock of any size

detached from a steep slope or cliff

that descend mostly through the air by

free falling and when we talk of the

debris fall it is the same as rockfall

but the material is smaller it is in

forms of debris

likewise the soil fall it is the same as

the rockfall but the material involved

in the soil

then we have the topple nest category is

topples it refers to those blocks of

frog that tilt or rotate forward on a

pivot or hinge

again it can be called as rock topple

debris stopple or soil tupple depending

on the type of the material so rock

topple forward rotation of a unit under

the action of gravity of the other

forces that created by the adjacent unit

or by

fluid in cracks

now next category the slides it refers

to the movement caused by the finite

shear failure along one or more surface

of the rupture which are visible or

whose presence may reasonably be

inferred very slow movement of the slide

is called a photograph show they creep

off in lower diving valley where the

road has creeped down well creep is an

extremely slows down movement of dry

surfacial matter

movement of the soil occurs in the

region which are subjected to freeze

though conditions slides are of two

types it is rotational and translational

rotational slides refer to a failure

which involves slight movement on a

circular or near circular surface of

failure

they generally occur on slopes of

homogeneous clay shale

weathered rocks and soil

the movement is more or less rotational

about an axis parallel to the contours

of the slope such slides are

characterized by a scarf at the head

which may be nearly vertical these

slides may be single rotational multiple

rotational or successive rotational

types single rotational slides a failure

which involves

sliding movement on a circular or semi

circular failure surface and multiple

rotational slides it many for

development of rotational movements that

includes two or more slip block each

with a curved slip surface tangential to

a common generally deep seated surface

it may be super imposed or juxtaposed

now coming to successive rotational

slide

as for rotational slip

but a successive slide consists of a

assembly of individual rotational slips

down a slope often of a shallower

undulation form

translation slides

are non-rotational

block slides involving mass movement on

more or less planar surface

the movement of translation slide is

controlled by weak surfaces such as

bedding

joints foliation

faults and shear zones the slide

material may range from

unconsolidated soils to slab of the rock

and the debris and these are classified

as block slides

slab slides and debris slides depending

upon the material involved as i

mentioned block slides are translational

slides in which the moving mass consists

of a single unit of a rock block that

moves down slope

it often possesses a graven at its head

slab slide as similar as for the block

slide but is fine material

it may not possess a grab one

because it may occur on a steeper slope

then debris slide a translucent slide it

covers debris that consists of many semi

independent units of disrupt nature

which may later adopt other forms of

movement and may turn into a very rapid

form may be called as diverse avalanche

it is a slide of a block now coming to

this translational slide which are

planar

in this the rock slide it is a

translational and planar movement of

rock units usually on a steep

bedded slope

it may develop into rocks of deborah's

avalanche fall and mudslide relatively

planar movement of softened agilistic

material

moving mainly on a pronounced silicon

side shear surface it advances chiefly

by sliding in elongated form on steeper

straight slopes or low bit

numbness category

is the spread it refers to the failure

caused by the liquefaction they where

saturated and loose sediments are

transformed into liquid state

normally earthquakes are responsible for

this phenomena

well flow

it refers to a rapid movement of

material as a viscous mass

it may be called as debris flow mud flow

or rock avalanche depending upon the

nature of the material involved in the

movement debris flow it is a rapid

movement of material which consists a

high proportion of coarse fragments

other granule solids water and air it

often possesses pronounced levees and

may have a sinus ridge form on hill

slope and the fans likewise mud flow

as is same as the debris flow but is

composed of fine material as you can see

a

culvert has slipped down

in one of the reasons in the hilly well

other than this we have also complex

landslides it is a category in which

combination of two or more number of

above type of movements are involved

such as rock fall plus debris flow it

may be rock slide plus rock avalanche it

may be topple plus rock etcetera so

these are the complex landslide now let

us know what are the causes of the

landslides

it broadly it is the slope failure

deforestation

unscientific forming hydrostatic

pressure

earthquake shocks intense rainfall and

cloud bursts and the development and

engineering activities now let's see one

by one

in case of slope failure

it is generally the steeper the slope

the greater the likelihood of occurrence

of a landslide landslide is a

gravitational phenomena hence slope

angle has a direct relation with the

slope stability as the slope angle

increases the gravitational forces

increase

thereby reduces the stability slope

becomes a concern when they achieve a

critical state of natural equilibrium

it becomes more critical

when rock mass overhang

along the downslope deforestation due to

deforestation soil of the area becomes

loose and fine material is loaded thus

poor spaces are developed which during

the rains are filled with water that

acts as lubricant to induce

downhill movement of material debris etc

barren slopes are more prone to erosion

that causes landslides

and land use changes

such as conversion of vegetative slopes

into buildup area also induce landslides

now another important cause is the

intense rainfall and cloud burst very

heavy downpour of rain suddenly at one

place

high rainfall coupled with drainage

network causes weakening of the

sediments and is also responsible for

high erosion seepage weathering and

leaching that all leads to trekking

landslides it is apparent that surface

morphology and subsurface sediments play

a major role in surface runoff and heavy

seepage

joint planes and cracks in rocks

and coarse grain sediments

loose boulder beds and other such

material all favors water percolation

and that cause excessive water pressure

within the sediments it is also known as

hydrostatic pressure it ultimately

increases shear stresses and decreases

shear strength of the sediments

the pore pressure also increases due to

sudden rise in water table for one

reason or the other as a result the mass

falls down or creeps slowly depending

upon the lithology volume of mass

gradient etc no erosion it is another

important cause

it is mainly along the rivers where

river water flows towards the bend

of the river with high velocity in its

outer edge

it causes rise in water level due to

centrifugal force as gravity pulls the

water downward water currents develop a

rolling spiral velocity against the bank

that erodes away the sediments it

creates an overhanging of the sediments

which collapse due to the weight of the

rock mass

earthquake shocks is another important

cause

earthquake shocks reduces the shearing

resistance along the fracture zones or

joint planes which in turns induce

landslides

in fact loose and unconstituted

sediments on the steep slopes become

vulnerable with the earthquake tremor

and that

induced landslides on scientific farming

particularly in the hilly region

the terrace cultivation of crops like

paddy cardamon etc that all needs

standing water

and this water slowly seeps inside the

ground and super saturate the hillside

which may cause landslides

now most important is the

developmental and engineering activities

the human

the landslide problem

has further been aggravated due to the

anthropogenic activities that is the

human interference

use of high power explosive during

construction of roads

dams or bridges etc may cause shattering

of the rocks

and later during the rainy season water

within the fracture zone may cause

landslides

the human interference has contributed

significantly causes instability of the

slopes

mainly in form of hill cutting for

construction of individual houses and

urban agglomeration

in fact nowadays people are

cutting the natural hill slopes

in a table land

for construction of buildings without

considering the engineering aspect the

removal of lateral support by man's

activity

is another cause of slow failure the

overloading of the hill slope is also

responsible for landslides as you can

see here a retaining wall has been built

to save the house

but such retaining walls when made

unscientifically they get toppered

resulting into unfortunate tragedies

likewise severe water seepages from

townships or villages

if this water is not channelized

it can induce unstability of the hill

slopes

thus human interference is also one of

the major causes of the landslides

now we have just learnt

what is a landslide

and what are the types and causes

as you can see the various causes but

most important the human interference

which causes landslides most

thank you

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you