>>what is TRUE north?
That's the northern point of our axis of rotation. Standing there, all directions are south of that point.
>>and what is magnetic north?
That's where the "North magnetic pole" emanates from the ground. (Also called the North Dip Pole, where the magnetic field dips in through the surface toward the source of magnetism at the core.) And, as noted previously - it can wander year to year.
>>and is a core the only explanation for magnetic fields on earth?
Not *all* magnetic fields, but certainly the one we're concerned with - it protects us from the charged particles of the solar wind. The liquid core is affected by Earth's spin, creating currents and eddies, and the moving, liquid iron in the outer core creates the magnetic field we use to navigate by. The movement of the liquid changes over time, which is why our magnetic poles "wander."
>>no materials scattered through the earths crust could account for this?
There *are* magnetic materials, and their small magnetic fields will add or detract to the overall field, but it's the movement of the liquid core itself that creates the dynamo that drives our magnetic field; it's a little smaller than Mars - so... it's quite huge.
>> Could Continental drift account for the differences IF there was no magnetic core?
No....
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Clive say: They're caused by different things, which don't necessarily match up. And I can't answer the question without explaining how it happened.
True north is the direction of the North Pole. The Earth spins around the line between the North Pole and the South Pole, and that's what determines when it's day and night, with the Earth spinning around that line once a day. So obviously it's important
The Earth also has a magnetic field, generated by hot liquid metal moving around in the outer core. The flow creates an electrical current, and by electromagnetic induction, that generates a magnetic field. If you have a magnetic field, it's going to have north and south poles. (The idea of a magnetic monopole - a north without a south, or vice versa - has been around for a while and there have been experiments to try and find one without success, so for ordinary purposes we can assume they don't exist.) Put a magnet in that magnetic field and of course it's going to want to line up with it, so it wants to turn to point north and south.