A mass movement that involves the sudden movement of a block material is called a rockfall.

Here's why:

* Rockfall is a type of mass movement where individual rocks or blocks of rock detach from a cliff face or slope and fall freely under the force of gravity. This is a rapid and sudden event.

Other mass movements, like landslides and slumps, can also involve blocks of material, but they are characterized by slower and more gradual movement.