When there is a lot of rainfall in a short period of time, the soil layer becomes unstable and slides down the sides of mountains.
(the soil layer; becomes; unstable; T:When there is a lot of rainfall in a short period of time) (the soil layer; slides down; the sides of mountains; T:When there is a lot of rainfall in a short period of time)
the soil layer the soil layer
becomes slides down
unstable T:When there is a lot of rainfall in a short period of time
the sides of mountains T:When there is a lot of rainfall in a short period of time