A slide of a large mass of dirt and rock down a mountain or cliff is called a landslide.

Here are some more specific terms for different types of landslides:

* Rockfall: A free-fall of rock fragments from a cliff face.

* Debris flow: A rapid flow of a mixture of rock, soil, and water.

* Mudslide: A rapid flow of mud, typically triggered by heavy rain.

* Slump: A slow-moving landslide where the ground moves downward and outward.

* Creep: A very slow, continuous movement of soil or rock downhill.

Let me know if you'd like to know more about any of these types of landslides!