Final answer:
The statement that earthquakes or heavy rains may trigger landslides is true. Factors like erosion, slope saturation, and seismic activity contribute to the occurrence of landslides.
Step-by-step explanation:
The statement that earthquakes or heavy rains may trigger landslides is true. Landslides are a form of ground movement that includes rock falls, deep failure of slopes, and shallow debris flows. Gravity acting on an over-steepened slope is often the underlying cause, but there are other factors that contribute to landslides. These include erosion by rivers, glaciers, or ocean waves, which may create unstable slopes, and rock and soil slopes can be weakened through saturation by snowmelt or heavy rains. Earthquakes can produce stresses on slopes, causing them to fail, particularly earthquakes with a magnitude of 4.0 or greater. In addition, volcanic eruptions can create loose ash deposits that, combined with heavy rain, lead to debris flows. The excess weight from the accumulation of rain or snow, or from man-made structures, can further stress these weak slopes, potentially leading to their collapse.