An intelligent person's science fiction movie. Very good.
Although the script is bit weak in a few spots (and there are some other minor flaws), this is outweighed by the excellent ensemble cast, good direction, good editing, excellent programmatic music, and excellent special effects. And gratefully - no gratuitous junk!
Overall, the movie is definitely worth seeing.
For those interested:
While there is debate in the scientific community as to the time and frequency, the earth's magnetic polarity does, in fact, shift periodically. This is proven in the geological record. North becomes South and South becomes North.
As to the core being a natural nuclear reactor that could, at any time, suddenly stop working, the only theory here is as to the when. And given that scenario, life on earth would be a whole different supposition.
Also, for general edification:
In the late 1960's and 70's there was experimentation done on creating and using earthquakes as weapons. (Human arrogance, greed, and stupidity have no limit. ) I have not (for a variety of reasons) kept up with the literature, so I don't know the current status of such blundering.
In any case, it is obvious that someone doesn't want that information proliferated. That goes right along with all the other censorship currently in vogue.
As for MAD - Mutually Assured Destruction - that is a mainstay of USA foreign policy.
Draw your own conclusions.