Answer:
B
Step-by-step explanation:
Revegetation would be pretty dramatic, but it would be boring beyond endurance to watch. Not A.
Gravity can be quite dramatic. Falling and your parachute won't open. That's dramatic and it is quick, but not the best answer.
A DrainPipe?: Maybe. But not as dramatic as the answer which is An Earthquake.
Sometime when you have nothing much to do search out earthquake pictures and see what comes up. Lots of movement. Quick. Lots moved.