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All about mass wasting


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I made this for my environment project - Mass Wasting. Thanks Pranav, Zubin and Adhish

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All about mass wasting

  1. 1. Adhish Luitel Prasil Koirala Begin Presentation >>>Pranav Bhandari Zubin Raj Bhandary Copyright©
  2. 2.  Definition: Geomorphic process by which soil, regolith, and rock move down slope under the force of gravity. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth, Mars, Venus, and Jupiters moon. When the gravitational force acting on a slope exceeds its resisting force, slope failure (mass wasting) occurs. The slope materials strength and cohesion and the amount of internal friction between material help maintain the slopes stability and are known collectively as the slopes shear strength. The steepest angle that a cohesionless slope can maintain without losing its stability is known as its angle of repose. When a slope possesses this angle, its shear strength perfectly counterbalances the force of gravity acting upon it.
  3. 3. Mass Wasting
  4. 4.  Types of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types: ▪ Creeps ▪ Landslides ▪ Flows ▪ Topples ▪ Slump Home > Types of Mass Movement
  5. 5.  Types of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorizedof smallbasic types:of soil or rock in + It is the combination into 5 movements different directions over time are directed by gravity gradually ▪ Creeps downslope. ▪ Landslides + The steeper the slope, the faster the creep. The creep makes trees ▪ shrubs and Flowscurve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing. ▪ Topples ▪ Slump + The surface soil can migrate under the influence of cycles of freezing and thawing, or hot and cold temperatures, inching its way towards the bottom of the slope forming terracettes. This happens at a rate that is not noticeable to the naked eye. Home > Types of Mass Movement >Creeps
  6. 6.  Types of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types: a well-defined + Where the mass movement has ▪ Creeps plane of sliding, it is called a landslide. This zone or ▪ Landslides slides, slumps and sturzstroms. includes rock ▪ Flows also one of the common classification of mass + It is ▪ Topples wasting ▪ Slump Home > Types of Mass Movement > Landslides
  7. 7.  Types of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5regolith that more + Movement of soil and basic types: ▪ Creeps fluid behavior is called a flow. resembles ▪ Landslides + These include avalanches, mudflows, debris ▪ Flows flow, lahars and sturzstroms. flows, earth ▪ Topples + Water, air and ice are often involved in enabling ▪ Slump fluidlike motion of the material. Home > Types of Mass Movement > Flows
  8. 8.  Types of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types: ▪ Creeps Topples are instances when blocks of rock ▪ Landslides pivot and fall away from a slope. ▪ Flows ▪ Topples ▪ Slump Home > Types of Mass Movement > Topples
  9. 9.  Types of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types: A slipping of coherent rock material along the curved ▪ Creeps surface of a decline. Slumps involve a mass of soil or ▪ Landslides other material sliding along a curved surface (shaped ▪ Flows like a spoon). It forms a small, crescent-shaped cliff, or abrupt scarp at the top end of the slope. There can be ▪ Topples more than one scarp down the slope. ▪ Slump Home > Types of Mass Movement > Slump
  10. 10.  Gravitational pull of the earth seismic shaking increased overburden from structures increased soil moisture reduction of roots holding the soil to bedrock undercutting of the slope by excavation or erosion weathering by frost heave Bioturbation Earthquake - Violent shaking due to an earthquake can cause unstable slopes to collapse Quick Clay- Soil liquefaction causes land to collapse … > Factors triggering mass wasting
  11. 11. ```Mass movements affects the following elements: The topography of the earths surface, particularly the morphologies of mountain and valley systems The quality of rivers and streams and groundwater flow The forests that cover much of the earths sub aerial surface … > Effects of mass wasting
  12. 12.  Cause floods by damming up bodies of water and result to huge loss of lives and property. Affect the agricultural lands Loss of industrial productivity because of interruption of transportation system by landslides. Increase the number of environmental refugees.
  13. 13. Mass wasting causing Avalanche as anroad damage example of mass wasting
  14. 14.  In a flow the material moved is not coherent but moves in a more chaotic, disorganized fashion. It flows with mixing with particles within the flowing mass as a fluid flows. Snow avalanches are one kind of flows. Where soil Is the flowing material these flos are described as mudflows. When a flow involves a wide variety of material is known as a debris avalanche.
  15. 15. Avalanche
  16. 16. + Mass movement can occur on a variety of scales and at a variety of rates. They mayinvolve a few cubic meters of material or more than a million cubic material.+ In the most rapid mass movements which include most rock falls and avalanchesand mudflow s, materials can travel at speeds of hundreds of kilometers per hour.+ There is little time for people to react once these events start and such events arethe cause of the greatest proportion of mass movement casualties. They also causeextensive damage to buildings.
  17. 17.  Landslides : can also be the cause of floods. A stream in the process of cutting a valley may cause unstable slopes. Landslides into the valley can dam up the stream flowing through it, creating a natural reservoir. The filling of the reservoir makes the are behind the dam uninhabitable
  18. 18.  Many types of construction lead to over steeping of slopes. Removal of material at the bottom of a hill may leave large rock masses unsupported. Building of houses on an unstable slope can lead to excess pressure being put on the slope. Planting of vegetation like trees can reduce the risk of unstable slopes and slides. Irrigation and use of septic tanks increase the flushing of water through soils and sediments. Artificial reservoirs can cause earthquakes as well as landslides. As the volume of the reservoir increases in volume, pressure exerted on the rocks along the reservoirs increases and the strength of the rocks also decreases. This may cause the dam to collapse.
  19. 19.  Slope reduction Retention Structures Fluid removal Other slope stabilizing method Recognizing the hazard Landslide Warnings
  20. 20.  Reducing the steepness of the slope Strengthening the slope by providing supporting materials at the base of the slope Reducing the load on the slope by removing all the large rocks or soil at the higher parts of the slope The measures that should be taken depend upon the stability of the slope. A highly unstable slope might require all these preventive measures to be taken at once. These steps should be carried out cautiously. For example, if earthmoving equipment is used the load of the equipment or the vibration caused by it might trigger the landslide
  21. 21.  The groundcover should be increased by the means of plantation. A plant that grows quick and that has a strong root system is preferred. Strong walls can be constructed on the basis of the magnitude of force that could act on the wall. The success rate of these kinds of structures has generally been low. Generally, high and thin walls have not been successful.
  22. 22.  Water is the most significant cause of mass movement. One of the basic ways of preventing landslide is to reduce the water pressure in the slope. Subsurface drainage can also be a method. Any kind of moisture removal system is highly encouraged due to which it become difficult for the rocks and soil to slide off as the frictional resistance to sliding increases.
  23. 23.  Vertical piles are placed on the base of the slope where the particles in the slope are solid. This is not to be used anywhere. If the soil contains more fluid, the soil will just come The use of rock bolts to stabilize rocky out or flow within the vertical piles. It is also slopes and rock slides has had a greater not applicable in highly steep slope. success. Rock bolts have been used in Generally, this technique is not very tunneling and mining. Sometimes the successful. process of driving giant steel bolts in to the stable rocks below the slip planes is also used. This works best in low angle slopes.
  24. 24.  Basic climatic feature, topography and geology cause mass movement in a place; they are independent of any human activities. Mass movements tend to recur in the same place where they commonly occur. It is very easy to recognize past rock falls in a vegetated area. Large rocks are not suitable in a vegetated area and remain barren. Lack of vegetation might also lead to past debris avalanche and slides. These kinds of factors lead the landscape to slope instability. . When there are small slips in the soil. The trunk of the tress grows a bit slanted but later vertical growth continues. If the gradual movement of soil is prolonged then the tree trunks maybe curved. Slanted utility poles and fences, tilting over of object can also act as an indicator of soil movement
  25. 25.  Landslide warning system was developed by U.S. geological survey after the rain triggered landslide in San Francisco Bay in 1982. The basis of the warning system was to establish a quantitative relationship among rainfall intensity, storm duration, and a variety of slope and soil characteristics relating to slope instability like slope angle, fluid pressure and so on. These relationships are established using factual data of past landslides. It became possible to estimate the limits of storm intensity and duration which when crossed might result in landslide, given it was known how saturated the ground was due to the recent precipitation. The system though incomplete was tested in February 1986. Of the ten landslides predicted, eight took place when forecasted.
  26. 26. Landslide warning
  27. 27. Or need more information?Available Topics.. •Mass Wasting •Factors causing it •Preventive Measures Bibliography: National Geographic Google Images Photo Bucket