The result of Earth's magnetic poles reversing over time is best represented by distinct bands in rocks that contain magnetic particles.
This phenomenon is known as magnetic striping and occurs at mid-ocean ridges, where new oceanic crust is formed. As magma rises and solidifies at these ridges, iron-bearing minerals within the magma align with Earth's magnetic field at the time of their formation. When the magnetic poles reverse, the orientation of these minerals aligns with the current magnetic field, creating distinct, parallel bands of rock with alternating magnetic orientations on either side of the ridge. This process provides important evidence for the theory of plate tectonics and the age of oceanic crust.