Why do we have a North Pole? It is a function of the earth's rotational axis, but why does this axis exist in the first place? Rotation is not an unusual property for heavenly bodies; it's the rule! The nature of the earth's spin is a natural consequence of our planet's origins as a much looser cloud of dust. As the dust became condensed into a solid sphere – a planet – it took on a definite spin, much the same way a figure skater's spin increases in speed as the skater's arms are brought closer to their body.
The geographic North Pole is not the same as the magnetic North Pole. In fact, the two poles are located about 1400 km apart. The wandering of the geographic pole has two origins: the movements of tectonic plates, and changes in the distribution of weight in the earth's mantle. The tectonic plates are in constant motion. This motion reflects the fact that the hard outer crust of the planet rests on a fluid layer called the mantle. Convection currents in the mantle result in the movement of the tectonic plates, thus the North Pole appears to shift. Consequently, a marker placed at the geographic pole will shift from year to year, as the underlying plate wavers. The point at which the rotational axis exits the mantle has not moved, just the earth's crust. This is called "apparent polar wandering." Earth's axis also wobbles slightly, so that the geographic pole revolves around a circle with a radius of 6 metres every 435 days.
Evidence is mounting that the rotational axis also changes position on a larger scale. We know that this axis is on a tilt, but the question we haven't yet answered is "why?" Perhaps collisions with other heavy objects knocked our planet off kilter; it has been suggested that the moon was formed from one such collision. Perhaps it has more to do with the nature of earth's composition; our planet is spherical, but its outer layers – the mantle and crust – are constantly shifting. Massive changes in the locations of continents causes a shift in the distribution of the earth's weight. For example, the continental plates were at one time joined to form the supercontinent Pangaea, and then split. Any imbalance from the movements of tectonic plates can cause a drastic rotation of the globe, with a shift of the rotational axis in relation to the earth's core to correct the unequal weighting. Some geologists have suggested that this shift – called true polar wandering – can occur as swiftly as ten degrees per million years. This means that in a span of 9 million years, the North Pole could have moved from the equator to the top of the globe! A few scientists believe that the earth has indeed done such a flip-flop at least once in its history!