The magnetic poles move, as do other parts of the Earth’s surface, because the outer core inside the planet is made of molten metal. As the Earth moves through space, spinning and circling the sun, there is some jostling that goes on, resulting in some shifting. And unfortunately, it doesn’t do so in a regular predictable fashion, which means changes to the surface of the Earth must be constantly monitored all over the planet. For reasons that aren’t exactly clear, New Zealand has been charged with monitoring the south magnetic pole, and has been doing so by traveling there every five years since the 1950’s.