It is the standard catastrophe theory that scientists have struggled with for ages. Namely, that periodically throughout history (the standard period is ~12,000 years but this can vary), the earth's crust seems to uncouple from the mantle, leading to massive displacements in the land masses. The oceans and atmosphere continue spinning in their original direction though, yielding a destruction that destroys everything on the planet and a new stone age environment with only a paltry few human survivors.

This is not new. Even Einstein worked on this problem. The theory is well known in scientific history and does seem to enjoy support in both scientific and religious texts. The problem has always been the process explaining how the crust "lets go" from the mantle. There have been various theories put forth throughout the centuries people have looked at this problem.

No idea why this particular hypothesis was classified. I personally think the sun micronova/electric plasma theory is much more plausible. The only thing I can see is that he mentions a nuclear explosion in the earth's core as the explanation, and the government didn't want a bunch of people worrying that nuclear testing might set this process off.

Otherwise, it is mostly mundane and repetitive. Not much original thought at all. But if the catastrophe theory is correct, it is likely the planet is due for another one within this millennium.

BTW, the sun micronova theory includes the idea that this event is usually predated by sudden migration of the earth's magnetic poles. The north magnetic pole wandering has sped up recently, moving around 50 miles towards Siberia in 2020 from a typical average of around 10. So it is possible we are much closer to the next instance of this catastrophe than we think. There is nothing you can really do about it if it is real. Survival is a matter of luck, and life afterwards will be extremely unpleasant. It is believed this is why flood narratives such as Noah are so pervasive throughout cultures.