When the giant comet positions itself exactly between the Earth and its Sun, things change. The Earth then has its greatest advocate for its previous alignment, the Sun and its magnetic alignment, negated. The Earth hears only the magnetic voice of the giant comet, so to speak, which stands between the Earth and its former magnetic commander, the Sun. You are aware that your Earth is heavier at its molten core, which is rumored to be composed primarily of iron. This is not entirely untrue, but regardless of the composition, the Earth's core is more sensitive to the magnetic alignment than the crust. The core grips the crust, and is not as liquid as one might think. There is friction. There is the tendency for the whole to move as one, despite their differing magnetic allegiances.
The pole shift is in fact a movement of the interior of the Earth, the core, to come into alignment with the giant comet. The 12th Planet, due to its massive size in comparison to the Earth, dominates the magnetic scene, and it is in this regard that gravity comes into the pole shift equation. The Earth's crust resists aligning with the giant comet, being caught in a web of magnetic pulls from its immediate neighborhood. In other words, the Earth's crust wants to stay with the old, established, magnetic pull, while the core of the Earth, having less allegiance and attachment to the neighborhood, listens to the new voice. There is a great deal of tension that builds between the crust of the Earth and the core of the Earth. This tension is released when the core of the Earth breaks with the crust, and moves. However, the core of the Earth drags the crust with it as it turns to align anew.
The pole shift is therefore sudden, taking place in what seems to be minutes to humans involved in the drama, but which actually takes place during the better part of an hour. There are stages, between which the human spectators, in shock, are numb. At first there is a vibration of sorts, a jiggling, as the crust separates in various places from the core. Then there is a Slide, where the crust is dragged, over minutes, to a new location, along with the core. During the slide, tidal waves move over the Earth along the coast lines, as the water is not attached and can move independently. The water tends to stay where it is, the crust moving under it, essentially. When the core finds itself aligned, it churns about somewhat, settling, but the crust, more solid and in motion, proceeds on. This is in fact where mountain building and massive earthquakes occur, just as car crashes do their damage on the point of impact, when motion must stop.
Weak spots among the Earth's crustal plates give way. The Pacific Ocean will shorten, and the Atlantic widen. Subducting plates will subduct greatly. Mountain building will occur suddenly, primarily increasing in areas already undergoing mountain building. All told, the better part of an hour, but at certain stages, only minutes. Plants survive as they are rooted and their seeds are everywhere, and animals including man survive because they travel with the moving plates of the Earth and experience no more severe a shock when the plates stop moving than they would during a Richter 9 earthquake. Where mountain building occurs when the plates stop moving, the stoppage is not simply a sudden jolt, like a car hitting a brick wall. All is in motion, and the stoppage is more like a car hitting a barrier of sand filled plastic barrels - a series of small jolts, occurring in quick succession.
At this time we estimate that the giant comet will come to within 14 million miles of the Earth. The strength of its magnetic field at that distance will be such that the comet's North Pole, angled essentially in the same direction as the Earth's North Pole, forces the Earth's North Pole to evade the pressure and accommodate its larger brother by swinging south to the bulge of Brazil. This alignment will not change if the distance between the sibling planets changes, but the speed and vigor of the shift would be so affected by a closer passage. The height of tidal waves and consequent inland inundation would be so affected. The heat of land masses above subducting plates where friction can cause the ground to melt, would be so affected. And the violence of shifting winds would certainly be so affected.