Physical Geology I Mass Wasting

Introduction to Mass Movements

Definition: Mass wasting, or mass movement, encompasses all types of down-slope movements of earth materials under gravity.
Types: Classified based on the rate of movement, type of material, and type of movement.
Classification of Mass Movements

Rate of Movement:

Slow movements: Such as soil creep, which might move as little as 1-2 mm per year.
Fast movements: Including rapid landslides or avalanches.
Type of Material:

Debris Flow: Predominantly coarse materials.
Earth Flow: Finer grain materials like clay and silt.
Mud Flow: Highly saturated materials with water, clay, and silt.
Type of Movement:

Flow: Viscous fluid-like movement, where the entire material is disturbed.
Slide: Movement along a defined plane, with relatively intact material.
Fall: Free-fall or bouncing from cliffs.
Common Types of Mass Movements

Flowage:

Examples: Debris flows, earth flows, mudflows.
Characteristics: Flow down-slope like a viscous fluid; can involve water saturation.
Creep:

Definition: Very slow movement of soil or rock down a slope.
Indicators: Tilted trees, fences, and gravestones; can cause structural damage over time.
Slides:

Translational Slides: Material moves along a planar surface.
Rotational Slides: Movement along a curved surface.
Rock Toppling: Complete fall of rock masses.
Falls:

Rock Falls: Sudden fall of rock from a cliff due to weathering, frost wedging, or wave action.
Factors Influencing Mass Movements

Slope: Steeper slopes are more prone to mass movements.
Elevation: Higher elevations, especially in mountainous regions, are more susceptible.
Soil Thickness: Thicker soil layers can be unstable.
Orientation of Weakness Planes: Planes parallel to the slope are more unstable.
Climate: Freeze-thaw cycles and precipitation increase instability.
Vegetation: Vegetation stabilizes slopes by binding the soil.
Case Study and Practical Considerations

Example of mass movements in the Himalayas, leading to natural dam formation.
Importance of understanding and mapping potential mass movement areas for civil engineering projects, especially in high-relief regions like the Himalayas.
Conclusion

Mass movements, including flows, slides, and falls, are significant geological processes impacting civil engineering.
Proper understanding and preventive measures are crucial to avoid structural damage and ensure safety in construction projects.