[Kevin Curry]

Someone said earlier something to the effect of that being like trying to crack an engine block with a firecracker.

Which makes sense--particularly with respect to suitcase nukes (which have yields of about .5 kiloton, IIRC). But what about a big nuclear device of, say, 1 megaton or larger? The most powerful nuclear device ever detonated, the Tsar Bomba, was close to 50 megatons but was based on a design yield of 100 megatons.

Drop a megaton-range device with a hardened casing from altitude so that it burrows deep into a natural fissure in the park, and detonate it. Might it not "crack the engine block"?

This may seem like foolish conjecture, but it does point up the wisdom of keeping Muslim militants from ever gaining access to nuclear weapons and delivery systems. I do not believe such a scenario would be beyond them. As desperate as they are to usher in a worldwide Muslim apocalypse, they might well relish the opportunity.

[Robert A Cook PE]

A surface blast is still no more than a half-mile-1 mile deep hole in the ground.

A long ways, but would it actually release pressure "safely" by destroying a natural park, or only delay it a few months or a few years, or release too much pressure prematurely?

The problem is predicting what happens if you vent the pressure, but release so much that catastrophe ensues anyway.

If you knew that Mt St Helens and Pinatubo were going to blow, but you couldn't prevent it, would you want to accelerate their schedule, or delay their schedule?