One of the hazards of adventuring is falling objects, such as from landslides and cave-ins. Depending upon the size of the falling objects and the area that they cover, and how close the character is to the edge, the GM may allow for an Acrobatics roll, minimum TN 20, for the character to attempt to escape the danger zone.
If the character is unable to escape, then he will likely take damage from things falling on him.
A landslide or avalanche is often very deadly. Anybody caught in the middle will take a +30 attack that does 10 points of Base Damage each round for the duration of the landslide (normally 2-10 rounds – roll 2d10, divide by 2).
A cave-in is like a landslide, but it is usually confined to a much smaller, enclosed area and it often does not last nearly as long as a landslide can. Cave-ins will last for 1-5 rounds (roll 1d10, divide by 2, round up), and they have an attack bonus of +20. The Base Damage for a cave-in is 10 points, the same as a landslide.
It is possible for there to be variations to both of these events. Some might be smaller and/or lighter while others might be longer, larger and/or be more damaging. The above rules represents the average cave-in and landslide.