Introduction to Mass Movement

A landslide is a rapid movement of a large mass of rock, soil, and debris down a slope, typically involving sliding or slumping. A rockfall involves the detachment and freefall of individual rocks from a cliff or steep slope. Landslides are often triggered by factors like heavy rainfall, saturation of soil, seismic activity, or human activities like deforestation or construction. Rockfalls, on the other hand, are primarily caused by weathering, erosion, and the weakening of rock structures due to freeze-thaw cycles, gravity, or seismic events.

Vegetation plays a crucial role in stabilizing slopes and reducing the likelihood of mass movement. The roots of trees and other plants bind soil together, increasing its cohesion and resistance to erosion. Vegetation also intercepts rainfall, reducing the amount of water that infiltrates the ground and potentially triggers landslides. Deforestation removes this protective vegetation cover, leaving slopes exposed and vulnerable to erosion. This reduces soil stability, increases water runoff, and significantly elevates the risk of landslides and other mass movement events.

The angle of repose is the maximum angle at which a pile of loose material, such as sand or gravel, can rest without collapsing. This angle is determined by the friction between the particles and their size and shape. When the angle of repose is exceeded, the slope becomes unstable and prone to mass movement events like landslides or rockfalls. The stability of a slope is directly related to the angle of repose, as slopes with steeper angles than the angle of repose have a higher risk of failure.

<p>Human activities can significantly contribute to the occurrence of mass movement events. Deforestation, urbanization, mining, construction, and agricultural practices can all disrupt natural slope stability. Deforestation removes vegetation, leaving slopes exposed to erosion. Urbanization and construction projects often involve modifying slopes and altering drainage patterns, which can increase runoff and lead to instability. Mining and agricultural activities can also weaken slopes by removing soil and vegetation, or by creating unstable conditions through excavation and irrigation.</p> Signup and view all the answers

<p>Creep is a slow, gradual downslope movement of soil and rock, often imperceptible to the naked eye. It is caused by repeated cycles of freezing and thawing, wetting and drying, or the expansion and contraction of soil due to temperature changes. Slumps, on the other hand, are more rapid and involve the downward sliding of a mass of soil or rock along a curved surface. They are typically triggered by saturation of soil, heavy rainfall, or seismic activity. The main difference between creep and slumps lies in their speed, the nature of movement, and the triggering factors.</p> Signup and view all the answers

<p>Factors that trigger mass movement include <strong>gravity</strong>, <strong>water saturation</strong>, <strong>slope angle</strong>, <strong>earthquake activity</strong>, <strong>volcanic eruptions</strong>, <strong>human activities</strong> (such as deforestation and construction), and <strong>geological conditions</strong> (such as weak or fractured rock).</p> Signup and view all the answers

<p>Water saturation can significantly increase the risk of mass movement. When soil or rock becomes saturated with water, its weight increases, which can exceed the shear strength of the material. Additionally, water can act as a lubricant, reducing friction between soil particles and facilitating movement.</p> Signup and view all the answers

<p>The angle of repose is the steepest angle at which a slope of loose material can remain stable. When the slope angle exceeds the angle of repose, the material becomes unstable and may fail, triggering mass movement.</p> Signup and view all the answers

<p>Human activities can contribute to mass movement in various ways. These include deforestation, which removes vegetation that helps stabilize slopes; construction and development, which can alter slope angles and drainage patterns; and mining and drilling activities, which can weaken rock and soil structures.</p> Signup and view all the answers

<p>Mitigation strategies include slope stabilization techniques such as retaining walls, rock bolts, and drainage systems to control water flow. Vegetation restoration can help anchor slopes. Early warning systems and land-use planning can also play a role in reducing risks.</p> Signup and view all the answers