Help with landscape thaw

First of all, thank you for your help and your time… :wink: I’m a true neophyte both with ue4 and with world machine… I would like to learn how to create an animation with a landscape that will be thawed. I’ve seen this very interesting video. How could I do it? In the description he talks about alpha masks … but I can not find any tutorials on how to create something dynamic (animated) applied to a landscape.