Tuesday, August 9, 2022

What Is Mass Wasting In Geography

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Identifying Locations Of Mass

What is Mass Wasting? | Geography | iKen | iKenEdu | iKenApp

The future mass-wasting can be estimated by analyzing past records. An inventory map can show the distribution and characteristics of mass-wasting in the study area . Mass-wasting events come in many shapes, sizes, and speeds. Typically, the steeper the angle of a slope, the faster the down-slope movement of rock and sediment. Also, water can play a significant role in mass-wasting, sometimes acting as the key component to a mass-wasting event, or serving as a lubricant within a mass of sediment and rock, enabling it to travel faster and further than it would otherwise. Types of mass-wasting mainly contain rock fall and rock avalanche, rock slide and slump, debris flow, earth flow, and creep.

Farmland terraces in the study area: field photo image from Google Earth.

From an inventory map, a mass-wasting susceptibility map can be produced. A mass-wasting susceptibility map was generated using a previous inventory map and remote sensing images. Seventy-one mass-wasting locations were surveyed in the four catchments and were used in further analysis. Fifty mass-wasting locations were randomly selected to build and train the models. The remaining 21 mass-wasting locations were used as validation data.

Vegetation Covers The Area

Plants such as grasses, shrubs, and large trees, help to hold rock materials together, thus reducing their movement on the earths surface.

Bare surfaces are more likely to experience mass wasting than surfaces that have vegetation cover.

The presence of dense vegetation cover in the wet regions increases the rate of water intake into the soil and to the rock beneath the surface.

This can speed up the saturation of the rock materials and trigger off mass wasting.

Chapter 15 Mass Wasting

Learning Objectives

After reading this chapter, completing the exercises within it, and answering the questions at the end, you should be able to:

  • Explain how slope stability is related to slope angle
  • Summarize some of the factors that influence the strength of materials on slopes, including type of rock, presence and orientation of planes of weakness such as bedding or fractures, type of unconsolidated material, and the effects of water
  • Explain what types of events can trigger mass wasting
  • Summarize the types of motion that can happen during mass wasting
  • Describe the main types of mass wasting creep, slump, translational slide, rotational slide, fall, and debris flow or mudflow in terms of the types of materials involved, the type of motion, and the likely rates of motion
  • Explain what steps we can take to delay mass wasting, and why we cannot prevent it permanently
  • Describe some of the measures that can be taken to mitigate the risks associated with mass wasting

What can we learn from the Hope Slide? In general, we cannot prevent most mass wasting, and significant effort is required if an event is to be predicted with any level of certainty. Understanding the geology is critical to understanding mass wasting. Although failures are inevitable in a region with steep slopes, larger ones happen less frequently than smaller ones, and the consequences vary depending on the downslope conditions, such as the presence of people, buildings, roads, or fish-bearing streams.

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On Mass Movement Pdf For Exam

Mass Movement, also known as mass wasting, represents the downhill movement of cliff material under the persuasion of gravity. It depicts the bulk movements occurring in soil and rock residue down slopes in response to rapid or steady sinking of the Earths surface in a vertical direction or the pull of gravity. Previously, the word mass wasting was used to reflect different processes by which huge masses of crustal substances are moved by gravity from one place to another.

What Are The Effects Of Mass Wasting

Mass Movement

Mass movements affect the following elements of the environment: the topography of the earths 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

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Landslide Classification & Identification

Mass-wasting events are classified by type of movement and type of material, and there are several ways to classify these events. The figure and table show terms used. In addition, mass-wasting types often share common morphological features observed on the surface, such as the head scarpcommonly seen as crescent shapes on a cliff face hummocky or uneven surfaces accumulations of talusloose rocky material falling from above and toe of slope, which covers existing surface material.

Classification Of Mass Wasting

It is crucial to classify slope failures so that we can understand what causes them and how to mitigate them. The three criteria used to describe slope failures are:

  • The type of material that failed .
  • The mechanism of the failure .
  • The rate at which it moved.

The type of motion is the essential characteristic of slope failure, and there are three different types of motion:

  • If the material drops through the air, vertically or nearly vertically, it is known as a fall.
  • If the material moves as a mass along a sloping surface , it is a slide.
  • If the material has internal motion, like a fluid, it is a flow.

Unfortunately, it is not typically that simple. Many slope failures involve two of these types of motion, some involve all three, and in many cases, it is not easy to tell how the material moved. The types of slope failure are summarized below.

Failure Type
Sand, gravel, and larger fragmentsFlowFast

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Causes Preceding Mass Movements

There are many activating factors preceding mass movements which are as follows:

  • Elimination of aid from below to substances above through natural or artificial means.

  • Removal of substances or load from over the original slope surfaces.

  • Haphazard elimination of natural vegetation.

  • An upheaval in height of slopes and gradient.

  • Overfilling through the addition of substances naturally or by artificial filling

  • Overburdening because of heavy rainfall, lubrication, saturation of slope materials.

  • Epodes of earthquakes and explosions etc.

Mass Wasting And Permafrost

Mass Wasting and Landslides – Types, Components, Causes and Prone Areas | Geography

In addition to falls, landslides, flows and creep, mass wasting processes also contribute to the erosion of landscapes in areas prone to permafrost. Because drainage is often poor in these areas, moisture collects in soil. During the winter, this moisture freezes, causing ground ice to develop. In the summer, the ground ice thaws and saturates the soil. Once saturated, the layer of soil then flows as a mass from higher elevations to lower elevations, through a mass wasting process called solifluction.

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What Is A Mass Movement

Mass Movement, also known as mass wasting, represents the downhill movement of cliff material under the persuasion of gravity. It depicts the bulk movements occurring in soil and rock residue down slopes in response to rapid or steady sinking of the Earths surface in a vertical direction or the pull of gravity. Previously, the word mass wasting was used to reflect different processes by which huge masses of crustal substances are moved by gravity from one place to another.

Factors Triggering Mass Wasting

Previously, the word mass wasting indicated a variety of processes by which large masses of crustal substances are moved by gravity from one place to another. Latterly, the word mass movement has been substituted to involve mass wasting processes and the sinking of restrained areas of the Earths ground surface. That said, Mass movements on slopes and sinking are often sustained by water and the importance of both types is the part each plays in the alteration of landforms.

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How material on surface move and by what process

How material on surface move and by what process

  • 1. 1
  • 2. MassMovements/Wasting2
  • 3. Group members Hassaan Ameer Umer Shahid Zain Ahmed Muhammad Bilal Rathor Haider Sikandar Zohaib Naseer Faizan Sabir3
  • 4. Contents Introduction Effects Controls of mass wasting Causes of mass wasting Classification Types of mass wasting Preventions Destruction by Mass Wasting Conclusion Reference4
  • 5. Mass WastingIt is downslope movement of masses of bedrock,rock debris, regolith or soil, under the directinfluence of gravity5
  • 6. Mass Wasting The downslope transfer of material through the directaction of gravity Component of erosion and transport of sediment Follows weathering, which weakens and breaks the rock6
  • 7. Effects Of Mass Wasting The combined effects of mass wasting and running water producestream valleys, which are the most common and conspicuous ofEarths landforms. If streams alone were responsible for creating the valleys in whichthey flow, the valleys would be very narrow features. Most river valleys are much wider than they are deep, is a strongindication of the significance of mass-wasting processes insupplying material to streams.7
  • 12. Controls of Mass Wasting Gravity Angle of repose Water Time Type of material Climate Vegetation12
  • 18. 18
  • 20. 20
  • 29. 29
  • 31. 31
  • 33. 33
  • 44. 44
  • Preventing And Delaying Mass Wasting

    A classification of mass

    Delaying mass wasting is a worthy endeavor, of course, because during the time that the measures are still effective, they can save lives and reduce damage to property and infrastructure. The other side of the coin is that we must be careful to avoid activities that could make mass wasting more likely. One of the most common anthropogenic causes of mass waste is road construction, and this applies to both remote gravel roads built for forestry and mining and large urban and regional highways. Road construction is a potential problem for two reasons. First, creating a flat road surface on a slope inevitably involves creating a cut bank that is steeper than the original slope. This might also involve creating a filled bank that is both steeper and weaker than the original slope. Second, roadways typically cut across natural drainage features, and unless great care is taken to reroute the runoff water and prevent it from forming concentrated flows, oversaturating fill of materials can result a specific example of the contribution of construction-related impeded drainage to slope instability.

    Apart from water issues, engineers building roads and other infrastructure on bedrock slopes must be acutely aware of the geology, especially of any weaknesses or discontinuities in the rock related to bedding, fracturing, or foliation.

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    Mitigating The Impacts Of Mass Wasting

    In situations where we cannot predict, prevent, or delay mass-wasting hazards, some effective measures can be taken to minimize the associated risk. In some parts of the world, similar features have been built to protect infrastructure from other types of mass wasting. Debris flows are inevitable, unpreventable, and unpredictable. The results have been deadly and expensive many times in the past. It would be costly to develop a new route in this region, so provincial authorities have taken steps to protect residents and traffic on the highway and the railway. Debris-flow defensive structures have been constructed in several drainage basins. One strategy is to allow the debris to flow quickly through to the ocean along a smooth channel. Another is to capture the debris within a constructed basin that allows the excess water to continue through but catches the debris materials.

    Theories And Models Of Debris Flows

    Numerous different approaches have been used to model debris-flow properties, kinematics, and dynamics. Some are listed here.

    • Rheologically based models that apply to mud flows treat debris flows as single-phase homogeneous materials
    • Dam break wave, e.g. Hunt, Chanson et al.
    • Roll wave, e.g., Takahashi, Davies
    • Progressive wave
    • A type of translating rock dam

    Calibrating and validating such sophisticated models require well-documented data from field surveys or minute laboratory experiments.

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    Mudflows And Debris Flows

    When a mass of sediment becomes wholly saturated with water, the mass loses strength, to the extent that the grains are pushed apart, and it will flow, even on a gentle slope. This can happen during rapid spring snowmelt or heavy rains and is also relatively common during volcanic eruptions because of the rapid melting of snow and ice. If the material involved is primarily sand-sized or smaller, it is known as a mudflow.

    If the material involved is gravel-sized or larger, it is known as a debris flow. Because it takes more gravitational energy to move more massive particles, a debris flow typically forms in an area with steeper slopes and more water than a mudflow. In many cases, a debris flow takes place within a steep stream channel and is triggered by the collapse of bank material into the stream. This creates a temporary dam and a significant flow of water and debris when the dam breaks.

    Factors That Control Slope Stability

    Form 3 Geography lesson 17 mass wasting

    Mass wasting happens because tectonic processes have created uplift. Erosion, driven by gravity, is the inevitable response to that uplift, and various types of erosion, including mass wasting, have created slopes in the uplifted regions. Slope stability is ultimately determined by two factors: the angle of the slope and the strength of the materials on it.

    A block of rock is typically situated on a rock slope that is being pulled toward Earths center by gravity. The vertical gravitational force can be split into two components relative to the slope: one pushing the block down the slope, called the shear force, and the other pushing into the slope, called the normalforce. The shear force, which wants to push the block down the slope, has to overcome the strength of the connection between the block and the slope, which may be quite weak if the block has split away from the main body of rock, or may be very strong if the block is still a part of the rock. If the shear strength is greater than the shear force, the block should not move. However, if the shear force becomes stronger than the shear strength, the block of rock will slide down the slope.

    Fractures, metamorphic foliation, or bedding can significantly reduce the strength of a body of rock, and in the context of mass wasting, this is most critical if the planes of weakness are parallel to the slope and least critical if they are perpendicular to the slope.

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    What Is Mass Wasting

    Mass wasting, sometimes known as slope or mass movement, is the large movement of soil, rock, and debris downhill because of the force of gravity. It is a natural phenomenon initiated by gravity but made possible by a combination of several factors. Modern geography has enlarged the definition of mass wasting to include natural erosion and the submerging of the earth’s surface. Mass wasting occurs along slopes such as hill or mountain sides and can result in significant alteration of the surrounding terrain. Mass wasting is a form of landslide.

    The Climate Of The Area

    The amount and nature of rainfall received in the area determine the amount of movement that will occur.

    The area which receives heavy rainfall experiences massive landslides, especially where the slope is steep.

    Light rain penetrates slowly into materials and may take a long to saturate it or may not saturate it at all.

    The resultant movement of the materials will therefore be slow. Alternate freezing and thawing encourage mass wasting as well.

    In a dry climate, materials may be loose but they lack the added advantage of the water. the resultant movement is therefore likely to be slow

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    Mudflow And Debris Flood

    One of the most spectacular forms of mass wasting and a potentially serious environmental hazard is the mudflow. This mud stream pours swiftly down canyons in mountainous regions . In deserts, thunderstorms produce rain much faster than it can be absorbed by the soil. Without vegetation to protect soil slopes, the excess water runs off, picking up fine particles to form a thin mud that flows down to the canyon floors and then follows the stream courses. As it flows, it picks up additional sediment, becoming thicker and thicker until it is too thick to flow farther. Great boulders are carried along, buoyed up in the mud. Roads, bridges, and houses in the canyon floor are engulfed and destroyed. The mudflow can severely damage property and even cause death as it emerges from the canyon and spreads out.

    Mudflows on the slopes of erupting volcanoes are called lahars. Heavy rains or melting snow turn freshly fallen volcanic ash and dust into mud that flows downhill. Herculaneum, a city at the base of Mount Vesuvius, was destroyed by a mudflow during the eruption of a.d 79. At the same time, the neighboring city of Pompeii was buried under volcanic ash.

    On steep slopes in mountainous regions, these flows are called alpine debris avalanches. The intense rainfall of hurricanes striking the southeastern United States will often cause debris avalanches in the hollows and valleys of the Blue Ridge and Smoky Mountains.

    Composition Of Slope Material

    Mass Wasting

    Another factor that determines mass wasting is the slopes material. Mass wasting is more prone on slopes that contain clay and shale. Without going into great detail here, the shape and composition of individual clay particles can absorb water and prevent water from peculating through the ground. A layer of clay on a slope can prevent water from filtering through the slope. Instead, the water stays near the surface and saturates the ground. This can cause the surface layers to lose friction and slide.

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    Ncert Notes: Mass Movements

    NCERT notes on important topics for the UPSC civil services exam. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams and so on. This article talks about Mass Movements.

    Mass Movements :-

    • Mass movement is also known as mass wasting.
    • It is the movement of masses of bodies of mud, bedrock, soil, and rock debris, which commonly happen along steep-sided hills and mountains because of the gravitational pull.
    • Gravity exerts its force on all matter, both bedrock and the products of weathering.
    • Hence, weathering is not essential for mass movement though it helps mass movements.
    • Mass movements which are sliding of huge amounts of soil and rock are seen in mudslides, landslides, and avalanches.
    • The air, water or ice does not transport debris with them from place to place but on the other hand, the debris may transport with it water, ice or air.
    • These are very active over weathered slopes rather than over unweathered materials.
    • Mass movements do not come under erosion though there is a shift of materials from one place to another.
    • Heave, flow and slide are the three forms of movements.
  • Mass movements can be classified into two major classes:
  • Rapid movements
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