system
Given the following post, respond as if you're commenting on Reddit:
human
If a waterfall is always flowing quickly how does one freeze?
gpt
The same way that even though water is constantly dripping from the ceiling of a cave, stalactites can still build up - little by little. A small amount of water will freeze at the very top of the waterfall, and this will provide a point at which more ice can build up on top. Over time, the ice will reach the bottom of the waterfall, giving the impression that the waterfall froze instantaneously.