What best describes the outer core's state?

What best describes the outer core's state?

• A. It is solid iron-nickel.
• B. It is gas.
• C. It is liquid iron-nickel moving.
• D. It is a plasma.

Answer: (C)

The Earth's outer core is a moving liquid layer of iron and nickel. This molten metal stays liquid because temperatures are far above its melting point at those depths, and it circulates due to convection driven by heat from below and by compositional differences. The flow of this conducting liquid generates Earth’s magnetic field through the geodynamo process, so a description of the outer core as liquid iron-nickel that is moving is the accurate one. The other states don’t fit: solid would describe the inner core, gas would require a different environment with much lower density, and plasma would mean ionized gas at even higher energy levels than present there.

The Earth's outer core is a moving liquid layer of iron and nickel. This molten metal stays liquid because temperatures are far above its melting point at those depths, and it circulates due to convection driven by heat from below and by compositional differences. The flow of this conducting liquid generates Earth’s magnetic field through the geodynamo process, so a description of the outer core as liquid iron-nickel that is moving is the accurate one. The other states don’t fit: solid would describe the inner core, gas would require a different environment with much lower density, and plasma would mean ionized gas at even higher energy levels than present there.