What Are the Magnetic Signals Preserved by Ancient Rocks?

Earth's surface was probably a magma ocean. It would have been constantly bombarded by giant asteroids left over from the birth of the solar system. This is where we come in and measure the magnetic signals that are preserved by ancient rocks to tell us how these rocks may have drifted horizontally over the surface. And what we found was that the Pilbara was drifting pretty quickly over Earth's surface back then, in fact at a similar rate to how fast the new world and old world are drifting apart due to plate tectonics right now.