Here's why:
* Seafloor Spreading: New oceanic crust is constantly being formed at mid-ocean ridges. As magma rises and cools, iron-rich minerals within the solidifying rock align themselves with the Earth's magnetic field at the time.
* Magnetic Reversals: The Earth's magnetic field flips its polarity, meaning the north and south magnetic poles switch places, every few hundred thousand years. This is a natural phenomenon that scientists have observed in the geological record.
* Magnetic Stripes: As new crust forms and magnetic reversals occur, the newly solidified rock records the orientation of the magnetic field at the time. This results in alternating bands of rock with opposite magnetic orientations, known as magnetic stripes.
The discovery of these magnetic stripes was a crucial piece of evidence supporting the theory of plate tectonics.
