Mass movement is an important topic in IB Geography, particularly within Option D: Geophysical Hazards. Mass movement refers to the downhill movement of weathered material under the force of gravity. These processes occur on slopes of all types and can be triggered by both natural factors and human activity. Understanding the different types of mass movement helps explain slope instability and associated hazards.

One major type of mass movement is rockfall. Rockfalls occur when loose rock breaks away from a steep slope or cliff and falls freely through the air. They are common in mountainous and coastal areas where freeze–thaw weathering weakens rock. Rockfalls happen suddenly and can be extremely dangerous, particularly near roads, settlements, or tourist areas.

Landslides are another important type. Landslides involve the rapid movement of material down a slope along a defined slip plane. They often occur after heavy rainfall, which increases the weight of slope material and reduces friction. Earthquakes can also trigger landslides by shaking unstable slopes. Landslides can destroy buildings, roads, and vegetation within seconds.

A more specific type of landslide is a mudflow or debris flow. These occur when large amounts of water mix with soil and loose sediment, creating a fast-moving, fluid mass. Mudflows are common in areas with steep slopes, heavy rainfall, or volcanic ash deposits. Because they move quickly and follow river channels, they can affect areas far from the original slope failure.

Slumping is a slower form of mass movement. It typically occurs on gentle slopes with weak or saturated materials such as clay. Slumping involves rotational movement along a curved slip plane, causing the upper part of the slope to collapse while the lower part bulges outward. Slumping is common along riverbanks and coastal cliffs and can be worsened by undercutting from erosion.

The slowest type of mass movement is soil creep. Soil creep is the gradual downhill movement of soil over long periods. It is caused by repeated expansion and contraction of soil due to temperature changes or wetting and drying. Although slow, soil creep can damage buildings, walls, and roads over time.

In IB Geography, it is important to recognise the factors that influence mass movement. These include slope angle, geology, water content, vegetation cover, and human activity. Deforestation, excavation, and construction can all increase slope instability by removing support or increasing load.

Overall, mass movement includes a range of processes from sudden, high-energy events like rockfalls and landslides to slow processes such as soil creep. Understanding these types helps explain slope hazards and informs strategies to reduce risk.

RevisionDojo helps IB Geography students understand mass movement clearly, linking physical processes, triggers, and hazards into structured, exam-ready explanations.