TOPIC:LAND SLIDING AND MASS MOVEMENT
SUBMITTED BY:
NIMRA BUTT (10020661-051) MARYAM FATIMA (10020661-010) HIRA TABASSUM (10020661-018) LARAIB SAMAN (10020661-024) AQSA ABID (10020661-034) ZEESHAN UMER (10020661-037) UMAIR MUSHTAQ (10020661-005) WALEED BUTT (10020661-017)
Outcomes
Land Sliding Causes of Landsliding Classification Types of landsliding Effects of landsliding Massmovement Occurrence Causes of Mass Movement Types of Mass Movement Kinds of Mass Movement
Land Sliding
A land slide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows
Landsliding(cont..)
Although the action of gravity is the primary driving force for a landsliding to occur
There are other contributing factors affecting
the original slope stability
Causes of Landsliding
Land sliding occurs due to changes from a stable to an unstable condition, A change can
be caused by a number of factors:Groundwater(porewater) pressure acting to
destabilize the slopeErosion of the toe of a slope by rivers or ocean
wavesEarthquakes adding loads to barely stable slopeVolcanic eruptions
Causes(cont..)
In many cold mountain areas snowmelt can be a key mechanism by which landslide initiation can occur.
Due to sudden increase in temperature.
Causes(cont..)
Water level change: Rapid changes in the groundwater level along a slope can also trigger land slides. This is often a case where a slope is adjacent to water body or a river.
Causes(cont..)
Rivers: In some cases failure is triggered as a result of undercutting of slope by a river, especially during a flood
Causes(cont..)
Seismicity: It is the second major factor in the triggering of landslides. Landslides occur during earthquakes as a result of two separate but interconnected processes: seismic shaking and pore water pressure generation.
Causes(cont..)
Human activities: Last but not the least is human activities, deforestation, cultivation, construction, shaking of machines and much more cause landsliding.
The table below shows the impact of mass-wasting processes on human life over the last century.
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 PeruEarthquake
related debris avalanche
70,000
2001 El Salvador Earthquake-induced landslide 585
2006 Philippines Rain triggered debris avalanche >1100
Landslide
Landslide is broken into:Slump
The downward movement of a block of material along a curved surface Do not move very far or very fast Upper surface sometimes tilts backward Leaves a crescent shaped cliff just above
the slump Common where the slope is
oversteepened and there is a lot of clayIt is also a type of Mass Movement
Cont..
Talus:A talus slope is developed by an accumulation of rock fragments at the foot of a cliff or ridge. Rock fragments break loose from the cliff above, roll down the slope and pile up in a bundle of rock rubble. Individual talus forms as a half-cone with the apex pointing upwards. In most cases a series of half cones join together around the base of a mountain.
Classification
They can be classified by:o Rate of movemento Type of materialo Nature of movement
Types of Landsliding
Debris flowEarth flowMud flowLahar
Debris Flow
Fast moving flow of mud and rocks Most numerous and dangerous of all the
landslides Begins during intense rainfall or snowfall They destroy everything in their path
Earth Flow
The wet ground breaks up and falls down a hillside in a rounded shape. It usually occurs on clay or sand and it is the slowest and driest type of flow.
Mud Flow
Also known as Mud slide, a mud flow is when the soil becomes so saturated with water that it speeds down the hill in a muddy river carrying debris. It is the fastest and wettest type of flow.
Lahar
“Lahar” is the Indonesian word for a “volcanic debris flow”. It is a volcanic, rapidly flowing mudflow that contains rock debris and water.
Effects of Landslides
1. Economic Decline: Landslides have certainly caused damage to property. This brings losses to the economy. “Economic rehabilitation is also needed in the area that has experienced a landslide”. This would cost a lot, and some of the offended country economy.
Effects(cont..)
2. Damage to infrastructure: Landslides can lead to damage to property resulting from the force flow or mud. Infrastructure land such as buildings, roads, places of leisure and so on can be destroyed by the landslide occurred.
Effects(cont..)
3. Loss of life: Loss of life is dangerous effect upon the occurrence of landslide and it is difficult to avoid, many lives will be lost upon the occurrence of landslides.
Mass Movement
Mass movement is the down slope movement of earth material under the influence of gravity.
How Mass Movement occurs
Mass movement occurs when masses of rock, earth, or debris move down a slope. They may be very small or very large, and can move at slow to very high speeds.
Mudflows (or debris flows) are rivers of rock, earth, and other debris saturated with water.
Causes of Mass Movement
Volcanic activity many times causes huge mudflows when the icy cover of a volcano melts and mixes with the soil to form mud as the magma in the volcano stirs preceding an eruption.
Mudslides can also develop when water rapidly accumulates in the ground, such as during heavy rainfall or rapid snow melt, changing the earth into a flowing river of mud or "slurry.".
Earthquake shocks cause sections of mountains and hills to break off and slide down.
causes(cont..)
Human modification of the land or weathering and erosion help loosen large chunks of earth and start them sliding downhill.
Vibrations from machinery, traffic, weight loading from accumulation of snow; stockpiling of rock or ore; from waste piles and from buildings and other structures.
However, the trigger mechanism for mass movement is the gravitational pull of the earth on soil, rocks, and mud.
Types of Mass Movement
Geologists classify mass movements based on the kind of material that move, how it moves and the speed of the movement
Types(cont..)
A rockfall occurs when rocks or rock fragments fall freely through the air Common on slopes that are too steep for
loose material to remain on the surface Many are a result of mechanical
weathering such as frost wedging or plant roots
Types(cont..)
Soil creep: It is nearly imperceptible to the naked eye as it is the slowest of all types of mass movement. Soil creep generally occurs in the top few meters of the surface and is accomplished by expansion and contraction of the soil.
Types(cont..)
Slide:A block of material moves suddenly along a flat, inclined surface If the slide includes segments of bedrock,
then it is called a rockslide Rockslides are among the fastest mass
movements often reaching speeds of over 124 miles per hour
Are usually caused by rain or melting snow Avalanches are a type of slide
Kinds of materials moved
Bedrock: Most common are slides or falls of small blocks of bedrock that break off by enlargement of joints during weathering. Massive rockslides or rockfalls involving much greater volumes of material are rare but are spectacular
Kinds(cont..)
Soil (Regolith): Mud and earth imply materials that consist mostly of clay and silt (mineral particles finer than sand). In a mudflow there is enough water to allow the mixture to flow easily.
Kinds(cont..)
Movements of snow and ice (snow avalanches and glacial flow) under the influence of gravity are not usually considered to be mass wasting. But sometimes snow is involved in mass-wasting events (as in the case of the event involving Nevada Huascarán in Peru in 1970).
Effects of Mass Movement
The morphologies of mountain and valley systems, both on the continents and on the ocean floors are changed
The character/quality of rivers and streams and groundwater flow is changed
It effects the forest that cover much of the sub aerial surface
It effects the habitats of natural wildlife that exist on the earth's surface, including its rivers, lakes, and oceans