Rock and Roll and Ants

The abhorrent ant behavior continues to escalate. This morning, I observed a large swarm of ants coalesce over a boulder. The machinations of the ants caused the boulder to move, rolling quite a distance, eventually lodging against the back gate of my yard. How the ants managed to move the rock are bewildering enough; managing the task without crushing a single member of the nest is unimaginable. The boulder, being of a size too large for me to move on my own, has rendered the back gate unusable at this time.  Their motivations for cutting off this egress on the part of the ants remains as mysterious as the behavior itself. I fear for what might come next.