Hollow Purple on a chemical level
It doesn’t really make sense for HP to ONLY leave a hole in the ground. Instead, local matter should remain in place, just in a new form. HP should forcefully rip molecules apart, then pull the atoms back together into new configurations. This process would add some kinetic energy, but not in a specific direction. So the end products would be a mix of lightweight gasses, that don’t explode, but quietly disperse into the surrounding air.