What you learned in school
Geology textbooks through the 1960s described the Earth's core as a single, solid mass of iron and nickel at the planet's center. Students learned about the core as a uniform solid ball, similar to a giant metal sphere, surrounded by the liquid mantle. This model was taught as established geological fact, with diagrams showing the Earth's interior as having distinct solid layers. The concept of a liquid outer core generating magnetic fields was not yet understood or taught in schools.
What we know now
Geology textbooks described the Earth's core as a solid mass of iron and nickel at the planet's center. Students learned about the core as a single, uniform solid ball surrounded by the mantle. Seismic wave analysis revealed that the Earth actually has two distinct core regions: a liquid outer core of molten iron and nickel, and a solid inner core. The liquid outer core's movement generates Earth's magnetic field through the geodynamo process. This discovery explained how Earth maintains its protective magnetic field and helped understand planetary formation.