> there is a minor north pole floating around the South Atlantic at the moment, which could presumably have you sailing in circles if relying on compasses
That sounds very interesting. Any sources?
By the way, I can almost imagine the beginning of the next Roland Emmerich disaster movie. A ship sinks while traveling in circles. Some clever scientist investigates the accident and deduces that the poles are going to switch next week. Nobody listens, so he must single-handedly save the world as well as his family.
[edit] Found a good description of the effects on compasses from a British Geological Survey article on magnetic reversals:
From these models and extrapolating down into the Earth, it is known that regions of reversed flux at the core-mantle boundary have grown over time. In these regions the compass points in the opposite direction, in or out of the core, compared to that of surrounding areas. It is the growth in area of such a reversed flux patch under the south Atlantic that is primarily responsible for the decay in the main dipolar field. This reverse patch is also responsible for the minimum in field strength called the South Atlantic Anomaly, centred over North-east Brazil. In this region energetic particles can approach Earth more closely, causing increased radiation risk to low Earth orbit satellites.
That sounds very interesting. Any sources?
By the way, I can almost imagine the beginning of the next Roland Emmerich disaster movie. A ship sinks while traveling in circles. Some clever scientist investigates the accident and deduces that the poles are going to switch next week. Nobody listens, so he must single-handedly save the world as well as his family.