Final answer:
The main factors that control and trigger mass movement are vegetation, slope steepness, water content, and earthquakes, which can destabilize soil and rocks, making slopes prone to failure.
Step-by-step explanation:
The factors that control and trigger mass movement are primarily vegetation, slope steepness, water content, and earthquakes. Vegetation affects soil stability, with roots holding soil in place and reducing the likelihood of mass movement. The steepness of a slope determines the gravitational force acting on soil and rocks, where steeper slopes are more likely to fail. Water content is crucial as it can lubricate particles and lead to increased weight, making slopes more prone to sliding, especially when the ground is oversaturated from snowmelt or heavy rain. Earthquakes can destabilize slopes by shaking the ground, thus increasing the risk of landslides. Other significant factors include soil composition, rock type, human activities such as deforestation and construction, which can contribute to weakening slopes or adding excess weight, and external forces like volcanic activity. Climatic factors such as temperature influence soil weathering and decomposition rates, ultimately affecting soil structure and stability.