Here's how it works:
* Magnetic Field Reversals: The Earth's magnetic field isn't constant; it periodically flips, with the north and south magnetic poles switching places. This happens over thousands of years and has occurred many times in Earth's history.
* Seafloor Spreading: New ocean crust is constantly being created at mid-ocean ridges. As magma cools and solidifies, magnetic minerals within the rock align with the Earth's magnetic field at the time.
* Magnetic Stripes: Because of the magnetic reversals, the seafloor has a pattern of alternating magnetic stripes, with rocks on either side of the ridge having opposite magnetic orientations. These stripes are like a "tape recording" of Earth's magnetic history.
Therefore, seafloor rocks are aligned according to the magnetic field that existed at the time they formed, which can be different depending on their age and location.
This phenomenon provides strong evidence for:
* Plate Tectonics: The theory that Earth's outer layer is divided into plates that move over time.
* Seafloor Spreading: The process of new ocean crust being created at mid-ocean ridges.
* Geomagnetism: The study of Earth's magnetic field.
