This document discusses landslides, defining them as the mass movement of material down a slope influenced by gravity and detailing various types such as rotational slides, translational slides, and debris flows. It outlines causes, including gravity, rainfall, earthquakes, and human activity, as well as the physical damage and casualties they can cause. Preventative measures suggested include selecting safe building locations, maintaining vegetation, and ensuring proper drainage to mitigate the occurrence of landslides.

1. WELCOME
BSC GEOLOGY FIRST YEARS
PRESENTS
M. E. S PONNANI COLLEGE
[SEMINAR]

2. NATURAL
HAZARDS

3. LANDSLIDES
TOPIC:

4. What is landslides?

5. A landslide is a mass
movement of
material,
such as rock, earth
or debris, down a
slope under the
influence of gravity.

7. Types of landslide

8. Rotational slides
occur on curved slip surfaces
where the upper surface of the
displaced material may tilt
backwards toward the scarp.

10. Translational slide
In this type of slide, the landslide
mass moves along a roughly planar
surface with little rotation or
backward tilting.

12. Rockfall
Rockfalls are abrupt movements of masses of
geologic materials, such as rocks and boulders, which
become detached from steep slopes or cliffs.
Separation occurs along discontinuities such as
fractures, joints, and bedding planes, and movement
occurs by free-fall, bouncing, and rolling. Falls are
strongly influenced by gravity, mechanical
weathering, and the presence of interstitial water.

14. Rock topling
Topple failures involve the forward
rotation and movement of a mass of
rock, earth or debris out of a slope.
This kind of slope failure generally
occurs around an axis (or point) at or
near the base of the block of rock.

16. Lateral spreading in fine-grained
materials on shallow slopes is usually
progressive. The failure starts
suddenly in a small area and spreads
rapidly. Often the initial failure is a
slump, but in some materials
movement occurs for no apparent
Lateral spreading

18. Debris flows are fast-moving
landslides that are particularly
dangerous to life and property
because they move quickly, destroy
objects in their paths, and often
strike without warning.
Debris flow

20. What are the Causes?

21. ● Gravity: Gravity works more effectively on steeper slope.
● Heavy and prolonged rainfall creating zone of weakness
also water table rises with heavy rain makes some slope
unsable.
● Earthquakes: ground vibrations creating during
earthquakes.
● Waves: wave action can erode the beach of the toe of the
bluff cutting into the slope and setting the stage for future
slides.
● Volcanoes

22. What are the after effects ?

23. ● Physical Damage: Debris may block the roads, supply lines
(telecommunication, electricity, water) and waterways
● Causaliteis: Death and injuries to people and animal
● Influence of landslides in dam safety: Failure of the slope
boarding the reservoir, flooding cause by movement of large
masses of soil into the reservoir.
● Landslides and flooding: Debris flow can cause flooding by
blocking valleys and stream channels forcing large amount of
water to backup causing flash flood
Direct effect
Indirect effect

27. How to Prevent ?

28. Landslides are a natural
phenomenon, and while we
cannot prevent them
entirely.

29. ● As experts suggest, reducing human interventions in ecologically
sensitive areas can help avoid exacerbating these disasters.
● Choose a safe location to build your home, away from steep slope
● Prevent deforestation and vegetation removal.
● Avoid weakening the slope
● ➤ Reforestation
● Drainage: Good ground drainage is essential to prevent saturation and
consequent weakening.
● ➤ Proper water runoff must be ensured by providing proper chanalisation

30. ● S D M A(State Disaster Management Authoritrhy)---
04712331345 ,1079
Available helpline numbers
● District Emergency Operation Centre (DEOC) -
1077

31. Major geological hazards (landslides)
occured in india

32. ● Wayanad,Mundakkai (2024)-debris flow
● Karanataka, ankola, shirur (2024)
● Guwahati, Assam. September 18, 1948. ...
● Darjeeling, West Bengal. October 4, 1968. ...
● Malpa, Uttarakhand. August 18, 1998. ...
● Mumbai, Maharashtra. July 12, 2000. ...
● Amboori, Kerala. November 9, 2001. ...
● Kedarnath, Uttarakhand. June 16, 2013. ...
● Malin, Maharashtra. July 30, 2014. ...
● Pettimudi, Kerala. August 6, 2020.

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