What is this animation and why is it happening? [duplicate]

Yes, I’ve seen this before. It’s a bug. That is the animation of a gym under attack, despite there being no gym at the center of it.

I’m not sure if you got this the same way as me, but I frequently get this visual bug when I check on one of my Pokémon that is currently defending a faraway gym (one that is not within range of me but that I can check on remotely) that is being attacked. The game (for some reason) moves the map to where the gym actually is while you view the gym screen and if it’s under attack, the fighting dustcloud will be rendered as well. Occasionally when I close out of the gym screen, the dustcloud continues to rage on. Opening and closing menus does nothing for me when this happens, I just close and restart the app, and everything is fixed.

It is a known bug.

it happens because you feed or looked at your pokemon in a gym you are defending and someone attack it in the same time.