Nicole Collingwood, of Balclutha School, asks :-

Why is the Earth like a magnet?

Gary Wilson, a geologist at Otago University and who specialises in palaeomagnetism, responded.

Well, I'm sure you know already that magnets are made up of blocks of the metal called iron (or sometimes called steel). In fact any block of iron is naturally magnetic. If you have a compass you can test this by taking a nail and bringing the point of the nail close to the compass. As you move the nail, the compass needle follows the direction you move the nail. When the nail is close to the compass it has much more effect than when the nail is far away from the compass.

Iron, itself, is a naturally occurring mineral. You can find it in various places on the surface of the earth. If you've ever been to the beach on the west cost of the North Island of New Zealand, you would find that it is black in colour and this is because the sand grains that make up the beach are in fact made of iron (if you haven't been there, you might be able to see a picture in a picture book of New Zealand).

This iron comes from the centre of the Earth. The centre of the earth is, in fact, a solid core of iron. And, just like the nail that you put close to the compass, all that iron is magnetic. Now, the centre of the earth is a long way away from Balclutha, but, there is more than a million times the amount of iron in the centre of the earth as in your nail, so you can still feel the effect of the magnetism from the iron core of the earth out at the surface of the earth in Balclutha.