Which statement about Earth's outer core is true?

Which statement about Earth's outer core is true?

• A. The outer core is solid.
• B. The outer core is gas.
• C. The outer core is a vacuum.
• D. The outer core is liquid and moving.

Answer: (D)

The outer core is molten iron and nickel that remains liquid under the extreme heat at Earth’s depths. The heat drives convection in this conducting liquid, so it moves in complex currents. That moving, electrically conducting fluid generates electric currents, and those currents produce Earth’s magnetic field through the geodynamo. It’s not solid, not a gas, and not a vacuum, so describing the outer core as liquid and moving best captures its state and behavior.

The outer core is molten iron and nickel that remains liquid under the extreme heat at Earth’s depths. The heat drives convection in this conducting liquid, so it moves in complex currents. That moving, electrically conducting fluid generates electric currents, and those currents produce Earth’s magnetic field through the geodynamo. It’s not solid, not a gas, and not a vacuum, so describing the outer core as liquid and moving best captures its state and behavior.