Final answer:
A rock slide can turn into a rock avalanche when the slope becomes over-steepened or weakened due to natural or human-made factors. Factors such as erosion, saturation, and earthquake-induced stresses contribute to the instability of the slope, potentially resulting in a rock avalanche.
Step-by-step explanation:
A rock slide can turn into a rock avalanche due to various factors. One of the main reasons is that the slope becomes over-steepened, either naturally through erosion by rivers, glaciers, or ocean waves, or by human-made structures. When the slope is weakened through saturation by snowmelt or heavy rains, or when earthquakes create stresses that make weak slopes fail, the instability of the slope increases, leading to a potential rock avalanche.