That fearsome place far beneath our feet where huge geological events take place and a few fictional books have been set.
According to the learned folk who write in to the last word, a section of New Scientistif the earth was reduced to the relative size of a squash ball, the dimples on that squash ball (deep sea canyons etc) would be smaller than those on a real sqaush ball.
As I've never actually seen the dimples on a squash ball, im going to reasonably assume that they are microscopic and possibly non-existant.
You can seem from this half-baked analogy that relative to the centre of the earth, the tiny sliver of air, water and dirt that we occupy is really small.
If you think about it, all life could be seen as a mould coating said squash ball.
Said mould would manage, improbably to survive several passing ice ages/ meteor impacts/ mass extinctions before evolving consciousness, choking on its own intellectual waste and devolving into people who shoot animals for fun, watch jerry springer, and die an appropriately stupid death - see darwin awards.
The earth is staggeringly huge and its depths practically infinite. The chance that humanity will have any impact at all on the serene depths is almost zero. Therefore It isn't surprising that when those depths move, and the symptoms (earthquakes,tidal waves etc.) kill or maim people by the thousand it is often seen as an action of god.
The depths of the earth are similar to the idea of god in many ways. Vast, serene, majestic, unknowable and (relative to us) possesed of infinite power - like and yet greater than the oceans that lie on its surface, the depths of the earth are akin to god.