Magnetic Stripes on the Ocean Floor: A Lab Simulation

This demonstration shows how the Earth's magnetic field has flipped (the N pole becoming the S pole, and vice versa) many times through geological time. It also demonstrates that as tectonic plates move apart, new rock is formed and locks in the direction of the magnetic field at the time. Students should realize that the discovery of stripes of alternately normal and reversed-magnetized rocks forming the ocean floor was a key piece of evidence convincing most geologists that the theory of plate tectonics was correct. This teacher demonstration shows how this works using magnetized pins stuck onto shaded paper in opposite directions, a plotting compass, and a bar magnet. Educational levels: High school, Middle school