Definitions of the landslides

A grassroots movement is a movement more or less brutal of the soil or sub-soil along a slope. Depending on the speed of movement, there are two types of ground movement : slow (progressive deformation, often imperceptible) and fast. Landslides involve changes to the landscape.

The manifestations of a grassroots movement

Predisposing factors

• Terrain and slope: A rock falls from the top to the bottom due to its weight and the force of gravity acting on it. The steeper the slope, the more movement!
• The type of ground: Depending on the nature of the soil (rock, earth, or sand), erosion can be more or less significant. Instability and movement depend on the type of soil.

Explanatory diagram of the landslides

Factors precipitating or aggravating

• Weather conditions such as heavy rain, wind, and drought contribute to the erosion of rock. Water seeps into cracks and causes materials to move out and become brittle. The soil becomes less stable.
• Human activity can also aggravate the problem of soil erosion. For example, construction that is too large, poorly organized, or that changes the nature of the soil (e.g., excavation or removal of boulders) can contribute to erosion. Furthermore, deforestation accelerates the process since tree roots have a stabilizing effect. However, vegetation material may also trigger falling blocks because roots can develop cracks in unstable blocks.

Source : Booklet teacher-cycle 4 – Project "Pare pa Pare" – French Red Cross – 2024

For more information :

Ground movement – NEMO – Government of Saint Vincent and the Grenadines. Explanations to understand what land movements are, how to deal with them and protect oneself before, during, and after. (English)

Movement of ground – Geohazards – French Government. Guide, explanations, practice sheets and French schemes earthquake (French)