Is there a mechanism to strongly heat up the Earth from the inside?

Question

Sorry for any errors; I'm Italian.

I'm working on a story where the Earth is devastated by a great geological cataclysm (strong earthquakes worldwide, volcanism bursting everywhere, large tsunami on all continents etc. ...).

My conclusion is that only two things could cause a catastrophe like this: tidal forces or a strong increase in the internal temperature of the planet.

The tidal forces are not well adapted to the story (although it is the most plausible solution), because any object capable of generating tidal forces strong enough to affect the Earth so much would alter the orbit of the planet, or destroy it completely.

So I focused on the heating. At the beginning I worked on research from 1997 which suggested that large clusters of dark matter, crossing the solar system could heat it (the dark matter would be captured by the planet and the sun, eventually reaching a critical mass and begin to annihilate, generating intense heat inside the planets and the sun). In this case I would only exaggerate the density of the agglomeration of dark matter, to immediately reach the critical mass and generate huge amounts of energy.

But looking more, I realized that this idea is quite outdated and so I shelved it, and have since been blocked because I can not find a plausible solution to the cataclysm (I could still use the dark matter, but the idea is not convincing), and I categorically refuse to use the phlebotinum (like mutants neutrinos of 2012).

So I was wondering, is there a plausible mechanism to heat the interior of the Earth, or at least to cause a cataclysm like the one described above without destroying the Earth? Or is my idea simply impossible?

PS: The cataclysm should not be fast; it happens over several years (nearly a decade). It began as a simple and small increase of geological activity, but then degenerated into a catastrophe that can seriously alter the Earth's geography.

Answer 1

Half the earths heat budget comes from radioactive decay of elements. There was 1.7 Billion years ago a natural nuclear fission reactor which ran on oxygen from the air and water with uranium ore in rocks; so not quite helpful to what you are asking but I think that is getting closer. Going from that example to a sustained nuclear fission deep in the mantle that happens within a relatively short time span of each other is much more problematic though, especially as to what would cause such a thing to happen.

However, knowing why it happens may not be as necessary as knowing that it already is in fact possible as noted by the Deccan Traps and the Siberian Traps. They may not be quite a universal in there features as you are looking for but they certainly did have universal impacts on climate and were massive in there extents. Those are probably plumes or hotspots as in Hawaii or Yellowstone; It is already known that having a strong earthquake happen in one place can trigger earthquakes and even volcanic eruptions (note the link gives examples where it does happen, but the purpose is to allay fears) both nearby and further away, so strong earthquakes and magma movements associated with a developing hotspot could easily trigger other eruptions and earthquakes, besides the primary effect of being itself a cataclysmic event.

If you really want to go with heating up the earth, deciding on some reason that sustained chain reactions were happening deep in the mantle would probably be the best bet; note that this would heat up the mantle but the heat transfer and/or convection of the mantle takes actually quite some time; whatever happened to cause the cataclysm would have already have happened and the effects would be felt over a (vastly) longer period of time.