Final answer:
Rockfalls are caused by fracturing along natural bedding planes and joints due to processes like erosion, saturation from precipitation, seismic activities, volcanic eruptions, and other man-made or natural weight increases. Earthquakes, particularly those above magnitude 4.0, can initiate landslides, and the process is exacerbated by over-steepened slopes and weakened rock structures.
Step-by-step explanation:
Factors Leading to Rockfalls
Rockfalls are a type of landslide characterized by the abrupt movement of rock down a slope. Natural bedding planes, joints, and faults are key features in rocks along which fracturing can lead to rockfalls. Erosion by rivers, glaciers, or ocean waves can create over-steepened slopes, enhancing the possibility of rockfalls. Additionally, saturation of rock and soil slopes through snowmelt or heavy rains weakens their structure, which can trigger slope failures.
Significant geological events like earthquakes can stress weak slopes causing rockfalls. In particular, earthquakes with magnitudes of 4.0 and above are known to initiate landslides. Also, volcanic eruptions can destabilize slopes by producing loose ash deposits along with heavy rain and debris flows. Another factor is the excess weight from accumulated rain or snow, the stockpiling of materials, or man-made structures, which may stress the slopes to failure.
Temperature changes can cause thermal stress leading to the expansion and contraction of materials which may also contribute to fracturing. For instance, hydraulic fracturing, which uses pressurized fluid to create fissures in rock for gas extraction, demonstrates the principle of pressure-induced fracturing. Over time, all these processes can lead to the weakening and eventual failure of rock slopes, especially along pre-existing weaknesses such as natural joints and faults.