Question

Cite the two main external factors that can enhance or trigger mass wasting processes. Describe how.

Short answer

Water and seismic activity are key external factors that enhance or trigger mass wasting.

Step-by-step solution

Identify External Factors

Mass wasting is the downslope movement of soil, rock, and debris under the influence of gravity. Two main external factors that can enhance or trigger these processes are water and seismic activity.

Explain the Role of Water

Water can add weight to the soil, reduce friction, and weaken the structural integrity of the slope materials. It can infiltrate into the ground, saturating and loosening materials, making them more prone to sliding.

Describe Seismic Activity's Impact

Seismic activity, such as earthquakes, shakes the ground and can disrupt the stability of a slope. Vibrations from an earthquake can dislodge materials, causing them to move downslope rapidly.

Key concepts

External Factors

Mass wasting refers to the process where soil, rocks, and other debris move downhill under the influence of gravity. Many factors can contribute to this natural occurrence, but certain external forces are significant in enhancing or triggering it.
These external factors disturb the stability of slopes, making them more susceptible to collapse. A primary role is played by water and seismic activity, each affecting the earth's surface in different ways:

• Water: Often involved in slope failure through saturation and increased weight.
• Seismic Activity: Earthquakes can instantly destabilize slopes.

Understanding these factors helps in mitigating risks related to landslides and similar phenomena.

Water's Effect on Slopes

When water infiltrates a slope, it brings significant changes to its stability. Water can add weight to soil and rock layers, which increases the gravitational pull on them, enhancing the likelihood of mass wasting.
Moreover, water acts as a lubricant between particles:

• Weight Addition: The extra weight from water can push materials downhill.
• Reduced Friction: Water reduces friction, making particles more likely to slide.
• Saturation and Weakening: Over time, water saturation can lead to loss of cohesion among particles, weakening the entire structure of a slope.

This makes slopes more prone to failure, especially during heavy rain or melting snow periods.

Seismic Activity Impact

Earthquakes represent another critical external factor impacting mass wasting. The strong vibrations produced during seismic events can have an immediate and dramatic effect on slope stability.
The shaking of the ground can lead to:

• Instant Displacement: Earthquakes can dislodge materials suddenly, causing them to move downslope rapidly.
• Crack Formation: Vibrations can cause cracks within the slope, further destabilizing it.
• Increased Landslide Risk: Even small tremors can set off landslides in areas already weakened by factors like water infiltration.

Recognizing seismic hazards is crucial for planning and managing developments in regions prone to such natural events.