Answer:
Magnetic field
Step-by-step explanation:
Magnetite is a very dense and strong magnetic mineral and is often found to be present in the rocks of oceanic crust which are basaltic in nature. According to the research, it has been observed that a zebra-like pattern has been found along the mid-oceanic ridge, with consecutive normal and reversed magnetic polarity.
When seafloor spreading takes place, the basaltic rocks containing magnetite are formed and this magnetite acts like a magnet that aligns themselves in the direction of the magnetic field of the earth, during the time of cooling.