You know, something I don't think is ever addressed in any TCB fic is what happens if you pop open that bubble. Now it greatly depends on if Equestria is actually hostile to Human life or if it's just the barrier, if the latter then this post isn't relevant. If the former, wouldn't all that thaumic radiation, depending on how far the barrier expands, get released into the atmosphere?

That would suck wouldn't it.

I actually imagined that if the barrier doesn't expand, the barrier would pop and the magic will just spewing out rapidly like a gas.

The Barrier is usually portrayed in one of two ways. The first as the edge of a dimensional expansion of the Equestrian Universe into ours. As such, it can't be 'popped', It's 'other space' intruding into ours, like those toys with the drops of colored oil in a larger container of clear oil. The other way is as a force field projected by a crazed Princess Celestia, which could be imagined as an expanding dome, which has an inside with magic and an outside without magic, which could be 'popped', but apparently not by any earthly weaponry. If this 'popped', theoretically the magic would escape in a fashion similar to radiation.
Also, in Equestira Girls, there are several scenes where Equestrian magic is seen escaping from the shattered statue in front of Canterlot High and it appears to be in a form of coherent energy.
It's magic, it doesn't need explaining.