Final answer:
Rock slides are commonly caused by factors such as intersecting joint planes, steep rock or soil slopes, overhanging rock blocks, and poor-quality rock or soil, especially under heavy rainfall, which contribute to weakening or stressing slopes to the point of failure.
Step-by-step explanation:
Rock slides are caused by a variety of factors that weaken slopes or stress them to the point of failure. These can include:
- Intersecting sets of joint planes, which can predispose the rock mass to failure under the force of gravity.
- Intact blocks of rock that are situated on steep joint or bedding planes, which may become dislodged.
- Overhanging rock blocks which can become unstable and result in a rockslide.
- Poor quality rock or soil that gets excessively saturated under conditions such as heavy rainfall, leading to a decrease in cohesion and an increase in weight, contributing to slope failure.
Contributing natural events include:
- Erosion processes such as the action of rivers, glaciers, or ocean waves, creating over-steepened slopes.
- Weather phenomena, particularly heavy rains or snowmelt, which can saturate rock and soil slopes, reducing their stability.
- Earthquakes of magnitude 4.0 and greater can trigger landslides by generating stresses in weak slopes.
- Volcanic eruptions that produce loose ash deposits and heavy rain leading to debris flows.
Excess weight on slopes from various sources, such as snow or rain accumulation, or human-made structures and activities, can also contribute to rock slide incidents by exerting additional stress on weak slopes.