In the first Austin Powers movie, Dr. Evil steals a 50 kiloton nuclear weapon, straps it to a drill and is going to fire it into the mantle to trigger volcanic eruptions world wide.
My instinct is that, compared to a lot of nuclear weapons in the megaton range, 50 kilotons is not really a lot, and using it to try to move rock (even molten rock) is not going to accomplish his goal. Would it even cause a measurable change in the pressure that far down?
Up through the 70s, US mad scientists kept trying to use nukes for digging. They didn’t accomplish much besides irradiating everything nearby, including the natural resources they were trying to extract
That’s a different kind of thing. Yes, they would have buried the bombs, but not that deep. Just deep enough to form a nice, deep and just slightly radioactive crater.
It would have been interesting to behold. There were plans to actually bomb a new Panama channel, several miles wide and without any locks. This would have resulted in a steady stream of water from the Pacific side to the Atlantic side, with basically unpredictable results.