Posted: Oct 24, 2005 12:18 am EST
Remember when we were kids, life was simple and Santa lived at the North Pole, which was opposite the South? That was before someone put a map and compass in our hands - and began to really complicate our world. Now two Magnetic Poles were added. Not only were they different from the Geographic poles, they also apparently kept moving around - if not reversing altogether.

And there's more. Ramón Larramendi on Antarctica, and the ‘Ice Warrior’ Jim McNeill in the Arctic, both hope to reach places such as The Pole of Inaccessibility, and the Geomagnetic Pole.

That makes a total of Eight poles on Earth. Knowing that, it even seems difficult to walk around without stepping on one!

Geography is easy

The most obvious Poles are the geographic ones - found on most maps, they indicate the furthermost Northern and Southern points on Earth.

The geographical North Pole (also known as True North) sits at 90° northern latitude. Located in the Arctic Ocean, which at this point has a depth of 4087 metres (13,410 feet), the place is usually covered by sea ice, and explorers can actually walk to it. However, as the ice is moving with the ocean drift there is nothing to mark the spot – so location tools such as GPS are required to find the exact furthermost northern point on earth.

You just can’t miss the South Pole

Quite the opposite - you can't miss the Geographic South Pole - at least not since 1958 when the The Amundsen-Scott South Pole Station was established there.

The permanently occupied South Pole station comprises several buildings built on on the 3000 m thick Antarctic ice cap, right at the furthermost sourthern point on earth.

Ceremonial South Pole

The ceremonial South Pole was set up for picture taking. There's a metallic sphere on a plinth, surrounded by flags of the Antarctic Treaty signatories. It sits a few hundred metres from the Geographic South Pole, which is marked only by a small sign and a stake.

The Magnetic switched poles

The magnetic poles are point areas of Earth's magnetic field, generated by the earth's iron core and spinning motion. The Magnetic Poles sit where the magnetic field lines come together, become vertical and enter Earth.

The magnetic poles wander considerable distances. Reaching the Magnetic poles is either difficult or easy, pending when you go for them. In the South it's pretty easy - you don't even have to ski to there; the SMP sits out in the ocean.

The NMP has become trickier to reach these days. For the first time since the 1600s, the Magnetic North Pole has now left Canadian territory and crossed into international waters, heading for Russia at more than 40 kilometres per year. You'll have to ski closer to 84 North to catch up with it.

The angular difference between Magnetic North and true (geographical) North varies with location, and is called the magnetic declination.

Flipping sides

Earth's magnetic field is subject to constant change (periods of strengthening and weakening) and shifts over time, eventually completely reversing its polarity. The last reversal happened 740,000 years ago and some researchers think our planet is overdue for another one, although nobody knows exactly when the next reversal of the Magnetic Poles might occur.

Geomagnetic Poles – the key of attraction
The Geomagnetic Poles are the poles of the Earth's geomagnetic field. The first-order approximation of the Earth's magnetic field is that of a single magnetic dipole (like a bar magnet), tilted about 11° with respect to Earth's rotation axis and centered at the Earth's core. The Geomagnetic poles are the places where the axis of this dipole intersects the Earth's surface.

Because the dipole approximation is far from a perfect fit to the Earth's magnetic field, the magnetic field is not quite vertical at the geomagnetic poles. The locations of true vertical field orientation are the magnetic poles, and these are about 30 degrees of longitude away from the geomagnetic poles.

Like the Magnetic North Pole, the geomagnetic north pole is a south magnetic pole, because it attracts the north pole of a bar magnet. It is the centre of the region in the magnetosphere in which the Aurora Borealis can be seen. Its present location is 78°30' North, 69° West, near Thule in Greenland.

The furthest points – poles of Inaccessibility

The North Pole of Inaccessibility, located at 84°03'N, 174°51'Wt, is the point farthest from any northern coastline, about 1100 km from the nearest coast. It is a geographic construction, not an actual physical phenomenon.

The position of the Southern Pole of Inaccessibility (85 deg 50 min S 65 deg 47 min E) is based on a calculations from the edges of the ice-shelves or a rocky coast. These are positions which may be reached by an icebreaker or similar vessel. It is thus reasonably constant and does not take account of seasonally variable pack ice (which is essentially a feature of the ocean rather than derived from the continental land mass).

I.E. As suggested by 'inaccessibility', this is the point furthest from navigable sea, rather than the 'theoretical' edge of the continent.

Note: Since first published this morning, the story has been edited with The Scott Polar Research Institute giving a 'truer' location and definition of the Southern Pole of Inaccessibility.

Up for more? Similar poles exist in the Pacific and Indian oceans. Phew.

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