The hell did I just find

I was moving a parasol around and upon lifting its base up I discovered this madness. I didn’t even realise it was ants at first because it all it looked like for a moment was a black smudge on the floor. A few seconds later they all disperse in every direction which is when I started recording. I’ve never seen anything like this especially with regular black ants. I’m aware some ant species bundle together to float on water or to bridge across a gap but why would they just do this on the floor?