Comment by peter303

Paleomagnetism measurement of the magnetic field direction in a rock gives the latitude of a the rock when it formed. The magnetic fields are horizontal at the equator and vertical at the poles, thereby giving latitude of the rock when is cooled from volcanic hardening or the last metamorphic squeeze. And there is a magnetic imprint when sediments settle too.

Latitude when combined with geometric constraints of seafloor strips and correlated trans-ocean rock formations build the overall picture.

In addition the oldest seafloor is 220 million years old or 5% of Earths lifetime. Paleomag measurements go back ten times longer.