The very center of the Earth is composed principally of which materials?

• A. Iron and nickel
• B. Silicate rock
• C. Gases
• D. Ice

Answer: (A)

The center is a solid inner core made mostly of iron and nickel. This comes from seismology and Earth’s density data: seismic waves reveal a very dense, metallic region at the middle, with a surrounding liquid iron-nickel outer core. The inner core stays solid because the immense pressures at Earth’s center keep iron in a solid state even though temperatures are high. The liquid outer core allows convection, which helps generate Earth’s magnetic field. Silicate rock forms the mantle and crust, not the center; gases and ice aren’t found there.