Classification of Mass Movement

Mass movement is the movement of rock, soil, and debris downhill due to gravity. It is classified by how fast the material moves, what the material is, and how it moves. Here are the main types of mass movement:

Types of Mass Movement

Creep: The slow, gradual downhill movement of soil and regolith (weathered rock material).

• Cause: Often caused by freeze-thaw cycles, where water freezes in the soil during the winter and thaws in the summer, causing the material to expand and contract. This slow process causes the material to move downhill over time.
• Characteristics: Creep occurs over a long period and is difficult to detect immediately. It can cause damage to structures like buildings and roads due to the slow displacement of the ground.

Slides: The sudden and rapid movement of material along a distinct plane, such as a landslide.

• Cause: Slides are typically triggered by external factors like heavy rainfall, earthquakes, or over-steepened slopes. These factors reduce the stability of the material, causing it to move suddenly.
• Characteristics: Slides can happen quickly and result in significant damage to the environment, roads, and infrastructure. The material often moves as a block or slab.

Flows: When material behaves like a fluid, flowing down a slope, often involving saturated soil or regolith.

• Examples: Mudflows, debris flows, and lahars (volcanic mudflows) are common types of flows.
• Cause: Flows are usually triggered by heavy rainfall or volcanic activity, which saturate the soil or loose material, making it flow downhill like a liquid.
• Characteristics: Flows can be very dangerous and fast-moving, often covering large areas and causing significant destruction.

Falls: The rapid free-falling of rock or debris from a cliff or steep slope.

• Cause: Falls occur when rocks or debris become loose and drop quickly due to gravity. This type of mass movement often happens in areas with steep rock faces or cliffs.
• Characteristics: Falls can happen suddenly and are often very destructive. The material can travel great distances, depending on the height of the fall.