Which core layer generates Earth's magnetic field and what is it made of?

• A. Outer core, molten iron and nickel
• B. Inner core, solid iron
• C. Mantle, silicate rocks
• D. Crust, basalt and granitic rocks

Answer: (A)

The magnetic field is generated by a dynamo in the outer core. In that layer, molten iron and nickel circulate due to heat and compositional differences, and Earth’s rotation helps organize these flows. This moving, electrically conducting fluid creates electric currents, and those currents generate and sustain the planet’s magnetic field. The inner core is solid iron-nickel, so it doesn’t flow like a liquid to drive the dynamo, though it influences convection patterns. The mantle and crust are solid rocks and are far less conductive, so they don’t support the large-scale currents needed for Earth’s magnetism. So the best answer is the outer core, made of molten iron and nickel.