The original concept that continents move slowly across the surface of the Earth was assumed to be true by empirically matching continental coastlines. Magnetometry is a way to finding magnetic data on the Oceans floor's. Meaning examining the variations in magnetic fields found on the floor's of various Oceans.

This show's how you can see the oceans floor's and how they are formed over millions of years, and show's you the magnetic fields how reversed itself many times.
This can also be used as a X-ray,evens as a heat censer. Magnetometry is almost like topography map. It shows how deep the density is on land, mountains and so forth.

external image Cheko-Magnetometry.jpgThis shows what Magnetometry maps looks like. looking at this map it's something like a topography map.