How material on surface move and by what process

1. 1

2. Mass
Movements/
Wasting
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3. Group members
 Hassaan Ameer
 Umer Shahid
 Zain Ahmed
 Muhammad Bilal Rathor
 Haider Sikandar
 Zohaib Naseer
 Faizan Sabir
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4. Contents
 Introduction
 Effects
 Controls of mass wasting
 Causes of mass wasting
 Classification
 Types of mass wasting
 Preventions
 Destruction by Mass Wasting
 Conclusion
 Reference
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5. Mass Wasting
“It is downslope movement of masses of bedrock,
rock debris, regolith or soil, under the direct
influence of gravity”
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6. Mass Wasting
 The downslope transfer of material through the direct
action of gravity
 Component of erosion and transport of sediment
 Follows weathering, which weakens and breaks the rock
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7. Effects Of Mass Wasting
 The combined effects of mass wasting and running water produce
stream valleys, which are the most common and conspicuous of
Earth’s landforms.
 If streams alone were responsible for creating the valleys in which
they flow, the valleys would be very narrow features.
 Most river valleys are much wider than they are deep, is a strong
indication of the significance of mass-wasting processes in
supplying material to streams.
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8. Effects of Mass Wasting
 Mass movements affect the following elements of the
environment
 The topography of the earth's surface, particularly the
morphologies of mountain and valley systems, both
on the continents and on the ocean floors
 The character/quality of rivers and streams and
groundwater flow
 The forests that cover much of the earth's sub-aerial
surface
 Habitats of natural wildlife that exist on the earth's
surface, including its rivers, lakes, and oceans.
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9. MASS WASTING
SLUMP NEAR BISMARCK,N.d
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10. Changes In Slopes
 If Mass wasting is to occur, there must be slopes
from which rock, soil, and regolith can move
down
 Earth’s mountain building and volcanic processes
that produce these slopes through sporadic
changes in the elevations of landmasses and the
ocean floor.
 If dynamic internal processes did not continually
produce regions having higher elevations, the
system that moves debris to lower elevations
would gradually slow and eventually cease.
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11.  Most rapid and spectacular mass-wasting events occur
in areas of rugged, geologically young mountains.
Newly formed mountains are rapidly eroded by rivers
and glaciers into regions characterized by steep and
unstable slopes. It is in such settings that massive
destructive landslides.
 Through time, steep and rugged mountain slopes give
way to gentler, more subdued terrain. Thus, as a
landscape ages, massive and rapid mass-wasting
processes give way to smaller, less dramatic downslope
movements.
11 Changes In Slopes

12. Controls of Mass Wasting
 Gravity
 Angle of repose
 Water
 Time
 Type of material
 Climate
 Vegetation
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13. Role of Gravity
 Gravity causes the downward
movement of rock body
 If gravity pull is greater than
resistive force then body will
move downward
AA
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RR
RR
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14. Forces due to gravity
 Two opposing forces determine
whether the body will remain
stationary or will move. These two
forces are shear stress and shear
strength.
Shear Stress
 force acting to cause movement of a
body parallel to the slope.
 There are two components of gravity:
(a) Perpendicular component (acts at
right angles to the slope)
(b) Tangental component (acts parallel to
the slope)
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15. Forces due to gravity
 As the slope becomes steeper,
the tangental component of
gravity increases relative to the
perpendicular component and
the shear stress becomes larger.
Shear Strength
 internal resistance of the body
to movement. This internal
resistance includes:
 (a) frictional resistance
 (b) cohesion between particles
 (c) binding action of plant roots
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16. Angle of repose
 Steepest angle at which material remains
stable
 Depends upon
 Particle size
 Particle shape
 Moisture Content
 Angle varies from 25 to 40 degrees
 Larger and more angular particles
maintain steepest angle
 Small and round particles do not maintain
steep angle
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17. Moisture effecting angle of
repose
 Moisture also increases the angle of repose of
sediments
 A small amount of moisture between sand grains
will bind them together due to surface tension.
Surface tension is the attractive force between
molecules at a surface
 Too much water will results in particles moving
freely over one another and therefore
dramatically reduces the angle of repose.
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18. 18

19. Role of Water
 Sedimentary rocks commonly have porosities of 10 -
30%
 If pore spaces fill with water, the weight of the material
is increased substantially, creating instability
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21. Role of Time
 Physical and chemical weathering can
weaken slope materials decreasing
resisting force. This causes the rock to
become very weak and mass wasting
occurs
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22. Role of Earth Materials
 Weak rocks(sedimentary) will weather quickly than
hard rocks(igneous, metamorphic)
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23. Role of Climate
 Climate plays a vital role in weathering of
material
 Climate influences the amount and timing
of water in the form of rain or snow
 Influences type and amount of vegetation
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24. Role of Vegetation
 Plant roots provide a strong interlocking network to
hold unconsolidated rocks and sediment
 Vegetation removes moisture from the soil
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25. ROLE OF TREES IN STABILITY
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26. Causes Of Intstability
Factors that either weaken cohesion forces or increase
downslope force
1. Heavy rainfall
2. Over-steepening of the slope
3. Slope Modification
4. Ground vibrations
5. Expansion/contraction cycles of soil/regolith
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27. Heavy Rainfall
 Addition of water in soil
 Lubricates the material
(decreases cohesion)
 Adds weight (increases
downslope force)
 Increases pore pressure
(increases downslope force
and decreases cohesion)
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28. Over-steepening of the Slope
 Can be human-induced or by natural
processes – increases the downslope
force.
 Stream undercutting a valley wall
(headward erosion, bank erosion, etc.).
 Waves cutting cliffs on a shoreline.
 Construction of roads, buildings, homes
etc.
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29. 29

30. Slope Modification
Removal of Vegetation
 Roots of plants and trees
hold regolith together
 Plants and trees remove
water from the soil
 Removal decrease
cohesive force
Building of structures
 decrease in cohesive force
or increase downslope
force due to added weight
will cause movement
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32. Ground Vibrations
 Earthquakes – triggers the rock and initiates its
movement
 Human induced – blasting for construction, large
equipment, etc.
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34. Expansion/Contraction Cycles
Movement of material due to
 Wetting and drying cycles
 Freeze-thaw cycles
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35. Classification of Mass
Wasting
 Type of Material
 Bedrock - Rock
 Unconsolidated material - Debris
 Soil
 Regolith
 Sediment
 Rate of movement
Fast moving, which are calculated in km/hr
 E.g. Rock avalanches moving up to speed of 200 km/hr
Slow moving, which are calculated in mm/yr or cm/yr
 E.g. creep
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36. Classification of Mass
Wasting
 Type of Motion
 FallFall – free-fall of detached particles, slope
steep enough that material falls to base
 SlideSlide – material remains cohesive and moves
along a well-defined surface
 FlowFlow – material moves downslope as a
viscous flow (most are saturated with water)
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37. Fall
 It is the free fall of
material of any size
 It fall directly to the base
of the slope or move in a
series of leaps and
bounds over other rocks
along the way
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38. Slides
 Slide occurring on a planar surface or on a slip plane
 Slide occurring along a curved slip plane
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39. FlowFlow
 Lahar flowing at surface
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40. Types of Mass Wasting
 Slump
 Rockslide
 Mudflow (Lahar, Debris Flow)
 Earthflow
 Creep
 Permafrost & Solifluction
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41. Slump
 Downward slipping (slide) of a
mass of rock or unconsolidated
material moving as a unit
 Rock or unconsolidated material
move in a curved path
 Does not move very fast or far
away
 May be single or multiple blocks
 Caused by overloading, excess of
water, over steeping, removal of
anchoring material
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42. Slump (a type of slide)
 Indicators:
 Scarp
 earthflow
 Anchoring material
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43. Rockslide
 Sliding of blocks of bed rock along a
defined slippage plane
 Sudden, rapid and destructive movement
 Takes place where rock strata are
inclined(steep slopes), joints or fracture exist
parallel to slope, underlying layer is thin
layer of clay or river cut the anchoring
material
 Can be triggered by rain falls or ground
vibration
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44. 44

45. Mudflow
 Rapid movement of debris containing large amount of water
 Water get mixes with rock debris, soil or regolith and forms a mud
which flow downward stream or mountain
 Characteristic of semiarid mountainous area
 Caused when snow melts quickly creating a flood or cloud burst
rapidly
Mudflow is of two types:
 Lahar
 Debris Flow
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46. Lahar
 WHEN debris flows
composed mostly of volcanic
materials on the flanks of
volcanoes are called lahars.
 Unstable layers of ash and
debris becomes saturated with
water
 They can occur either during
an eruption or when a volcano
is quiet. They cause mass
destruction of land and life.
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47. Debris Flow
 Mixture of rocks debris or soil
& water
 Moves as a viscous fluid
 Common after heavy rains
 Rapid movement – up to 50
km/hr, the more water present
the faster the rate of movement
 Common in semi-arid regions
and along volcanoes (lahars)
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48. Earthflow
 A type of debris flow, generally
move slower
 Forms on hillside humid areas
as a result of excessive rainfall
 Water saturates the clay-rich
regolith and material break
away and flow a short distance
downslope
 Speed of earthflow vary from
few meters per hour to several
meters per minutes
 Can remain active over periods
of years
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49. CreepCreep
 Gradual downslope
movement of soil or
regolith– mm/yr
 Expansion/contraction,
freezing/thawing or
wetting/drying cycles
play a key role
 Process so slow one
cannot observe it in action
 Enhanced by burrowing
organisms, periods of
prolonged rains or snow,
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51. Permafrost
 Layer of permanently frozen ground, known as permafrost,
occurs where summers are too cool to melt more than a
shallow surface layer
 It refers to the permanently frozen ground that occurs in
climates in which annual air temperature is low enough to
maintain a continuous surface temperature below 0C
 Depth to which water freezes exceeds the depth of summer
thawing
 The water in soil underlining does not melt
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52. Solifluction
 Special type of creep
 Occurs in regions underlain by
permafrost (permanently frozen,
water-bearing ground)
 During warm periods top
portion (active layer) thaws and
becomes saturated
 Melt waters are unable to
percolate into permafrost layer
below
 Saturated (active) layer flows
over frozen layers
 It can occur on slopes as gentle
as 2-3 degree
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53. SOLIFLUCTION
 In mat of vegetation Solifluction move downward in well-
defined lobes or overriding folds
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54. MASS WASTING PREVENTION
 Move material from the top to the toe.
 Build barriers.
 Build retaining walls.
 Drain the slope.
 Plant vegetation.
 Prevent flooding.
 Prevent undercutting.
 Don’t over-steepen slope.
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55. RETAINING WALLS55

56. Destruction caused by mass
wasting56
year Location Type Fatalities
1916 Italy, Austria Landslide 10,000
1920 China Earthquake triggered landslide 200,000
1945 Japan Flood triggered landslide 1,200
1949 USSR Earthquake triggered landslide 12,000-20,000
1954 Austria Landslide 200
1962 Peru Landslide 4,000-5,000
1963 Italy Landslide 2,000
1970 Peru Earthquake related debris avalanche 70,000
1985 Columbia Mudflow related to volcanic eruption 23,000
1987 Ecuador Earthquake related landslide 1,000
1998 Nicaragua
Debris avalanche and mudflow tirggered by heavy
rains during Hurricane Mitch
~2,000
2001 El Salvador Earthquake-induced landslide 585
2006 Philippines Rain triggered debris avalanche >1100
2009 Taiwan Typhoon Marakot triggered landslide 397
2010 Gansu, China Rain triggered mud flows 1287
2013 Northern India Heavy rain triggered landslides 5700

57. Conclusion
 Mass wasting is the movement of earth material
under influence of gravity
 It is responsible for shaping the earth and
forming different land forms
 It causes destruction to humans beings if it
occurs in living areas
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58. References
 Monroe, Wicander (2005). The Changing Earth: Exploring
Geology and Evolution. Thomson Brooks/Cole.
 Tarbuck, E.J.; Lutgens, F.K. (1998), Earth, an introduction to
Physical Geology (6th ed.)
 Easterbrook, D. J. (1999), Surfaces Processes and Landforms
(2nd ed.)
 http://www.britannica.com/science
 http://www.study.com/academy
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