MASS

WASTING /
MASS
MOVEMENT

BY Ma Kaythi Kyaw
Kyaukse University
Department of geology
Contents
❖ Introduction
❖ Classification of mass movement
❖Mode of movement method
❖ Type of mass wasting
❖Factors Influences of mass wasting
❖Important of mass wasting
❖ Some Record of land failures in Myanmar and other Country
❑ INTRODUCTION

➢ Mass Wasting /Slope Failures/ and

slide refers to all downslope
movement of rock, regolith, and soil
under the influence of gravity. Speeds
Range from extremely fast to
extremely slow.
How are mass movements classified ?

➢ Material: Type of material that failed (typically either bedrock

or unconsolidated sediment)
➢ Motion: How the material moved (fall, slide, or flow).
➢ Rate: Speed at which the material moved.
MODE OF MOVEMENT METHOD IN MASS WASTING

❖ Slide
➢ In slide movement, motion is
maximized along the base of the
moving mass
➢ Usually, the top of the mobile surface
is able to keep pace with the rate of
motion along the base, but sometimes
it may lag behind
➢ The slide can take place in absolutely
dry matter. Hence it can happen
anywhere
➢ the presence of water facilitates it and
induces greater speed.
 ii . Flow Method

➢ In flow mode, the maximum speed at the top, while the

rate of movement diminishes with increasing depth till it
reaches zero along the shear plane.
➢ In this mode, water is an essential component of the
process
➢ As such, it is a feature of humid regions.
iii . Heave Method

➢ The rate is mostly very slow

➢ Caused by freezing then thawing, or hot then cold
temperature, it causes surface soils to move up then
down
➢ Eg – Creep
TYPE OF MASS WASTING

➢Flow
❑Creep
❑Debris Flow/Mud Flow/ Earth Flow
❑Solifluction

➢Slide
❑Slide / Slump

➢Fall
Creep Flow

- long term mass-wasting

process
- not noticeable to the naked
eye
- Caused by freezing then
thawing, or hot then cold
temperature, it causes surface
soils to move up then down
- Eg – Soil Creep
Mudflow and earthflow

Mudflow Earthflow
• mudflows are predominantly sand ,mud and fine- • earthflows are predominantly sand ,mud and fine-
grained particles mixed with water grained particles mixed with water
• Some mudflows have the consistency of wet • An earthflow contains less water than a mudflow
concrete and is therefore less Fluid
• its high water content and so more fluid than • Rapid movement
earthflow
• Water is main factor
• at speeds up to 100 kilometers per hour
• Rapid movement
• Water is main factor
California Mudflow in 2018

Earthflow
 Debris Flow

➢ Downslope flow of relatively coarse material

➢ >50% of particles of debris flow are coarse than sand
➢ They developed when water rapidly accumulate in the
ground and during heaving rainfall and rapid snow melt
➢ May be very slow or very fast movement
➢ Contain less water
 Solifluction
➢ Occur mainly in colder areas, when freeze
and thaw create movement
➢ water mixed with soil forms clay with moves
as a thick viscous fluid
➢ flows at a rate of 0.5 to 5 centimeters per year.
➢ Slow movement
Slide
Land slide Slump

• the mass movement has a well-defined zone or • Only straight movement

plane of sliding, it is called a landslide.
• Rotational slide
• Only straight movement
• The material moves along a curved surface
• Translational slide
• Creates a distinctive spoon-shaped fratured
• The material moves along a flat, planer surface
• Slumps commonly occur in areas with weak,
• Slides often occur on steep slopes cohesive soils or sedimentary rocks and are often
triggered by factors like saturation from rainfall
• Rapid movement
or undercutting of the slope's base.
• Rapid movement
 A landslide on Kennon
Road during a 2015 typhoon

Slump
 Fall
➢ Rapid movement
➢ Rock of any size fall through the air
➢ Recall from our discussion of weathering that when water
freezes and thaws, the alternate expansion and contraction can
dislodge rocks from cliffs and cause rockfall.
➢ Eg- Rockfall
FACTOR INFLUENCES OF MASS WASTING

I. The Angle of the Slope

• The Steeper the slope, the faster the
movement
• because gravity becomes stronger with
increasing the angle of the slope.
• Excavation for roads cuts and hillside
building sites are major cause of slope
failures
ii .Weathering and Climate

➢The area which receives heavy rainfall

experiences massive landslides, especially
where the slope is steep.

➢As soon as solid rock is exposed at the

Earth's surface, weathering disintegrate and
decompose it, and reducing its shear
strength and increasing its susceptibility to
mass wasting

➢Common in areas of deep weathering

 iii . Water content
➢ Large amount of water from melting snow on heavy rainfall greatly
increase the likelihood of slope failure.
➢ The amount of water in rock or soil influences slope stability
 iv. Vegetation

➢ Absorbing the rain decreasing water

saturation of slope's material leads to
Loss of shear strength

➢ Root system also helps stabilize a slope

by binding soil particles together
v. shear strength.

➢ When the gravitational force acting on a slope exceeds its

resisting force, slope failure (mass wasting) occurs
➢ The resisting forces helping to maintain slope stability
➢ Its called shear strength
 vi. Over loading

➢ the result of human activity and typically results from dumping, filling,
or piling up of material.

➢ The additional weight created

by overloading increases the
water pressure within the
material, which in turn
decreases its shear strength,
thereby weakening the slope
material.
 vii. Geology and structure

❖ The relationship between topography and the geology of an

area is important in determining slope stability
❖ If the rocks underlying a slope dip in the same direction as
the slope, mass wasting is more likely to occur than if the
rocks are horizontal or dip in the opposite direction.
 viii. Triggering Mechanisms

➢ The most common triggering mechanisms are strong vibrations

from earthquakes and excessive amounts of water from a
winter snow melt or a heavy rainstorm.

2021 Fukushima
earthquake cause landslide
in Japan
IMPORTANT OF MASS WASTING

➢ Mass-wasting is an important part of the erosional process, as it moves material from higher elevations to
lower elevations
➢ Mass-wasting processes are occurring continuously on all slopes; some act very slowly, others occur very
suddenly, often with disastrous results.
➢ As human populations expand and occupy more and more of the land surface, mass-wasting processes
become more likely to affect humans.
➢ Rapid mass wasting events such as massive landslides or debris flows are typically triggered by events that
destabilize material that resides on steep slopes. Such events include earthquakes, volcanic eruptions, rain or
melting snow, and poorly planned landscape alterations by humans (e.g. road cuts or developments that
require the removal of material at the bases of slopes)
➢ Knowledge about the relationships between local geology and mass-wasting processes can lead to better
planning of a region that can reduce the vulnerability of such natural hazards.
Some Record Land failures in Myanmar

Phakant Township,Kachin State , Jademine

Slope Failures
August 11,2019 In south-eastern Myanmar, Mon
State , ThelPhyuGone Village landslide
Location: Kedarnath, India
Date: June 2013
Casualties: 5,700
Location: Gansu, China
(especially city of Zhouqu)
Date: August 8, 2010
Casualties: Over 1,500
 Sierra Leone
Mudslides
Location: Freetown/Reg
ent, Sierra Leone
Date: August 14, 2017
Casulaties: 1,141
THANK YOU