What is the primary material composition of the outer core?

The outer core of the Earth is primarily composed of molten iron and nickel. This layer is found beneath the mantle and above the solid inner core. The temperatures in the outer core are high enough to keep these metals in a liquid state, which is crucial for the geodynamo effect that generates Earth's magnetic field. The movement of the liquid metal in the outer core creates electric currents, which in turn produce magnetic fields. This is essential not only for navigation but also for protecting the planet from solar radiation.

The presence of molten iron and nickel distinguishes the outer core from the inner core, which is solid due to even higher pressures that force the metal into a solid state. Other materials listed in the choices, such as granite and basalt, are primarily found in the Earth's crust rather than the core, highlighting the unique composition of the outer core that's critical for understanding Earth's structure and magnetic field generation.