When molten material hardens into rock on the ocean floor the domains of the iron it contains what?

When molten material hardens into rock on the ocean floor, the domains of the iron it contains align with the Earth's magnetic field at that time. This alignment occurs as the molten rock cools and solidifies, effectively locking in the magnetic orientation. As a result, the rocks serve as a historical record of the Earth’s magnetic field, allowing scientists to study past geomagnetic reversals and plate tectonics.