MTTC Missed Topics Practice Test

The magnetic north drifts because the Earth's magnetic field is generated by the geodynamo in the liquid iron of the outer core. As the conducting fluid in the outer core moves in changing convection patterns, it creates and continually reshapes electric currents, which in turn sustain the magnetic field. When these flow patterns shift, the surface field reorganizes, so the location where the field points vertically downward (the magnetic north) moves over time—a process known as secular variation. The solid inner core evolves slowly and does influence the field only weakly in the long term, while the mantle and crust are rigid and don’t drive the drift. Crustal magnetization can create small, localized features, but the large-scale drift comes from the outer-core dynamics.