Correct Option
The correct option is Liquid.
Explanation
The Earth's interior is stratified into distinct layers based on chemical composition and physical properties: the Crust, Mantle, Outer Core, and Inner Core. The Core is the innermost region, composed primarily of heavy metals such as Nickel and Iron (NiFe).
Detailed Analysis
The physical state of the Core is divided into two distinct zones based on the behavior of seismic waves and pressure-temperature dynamics:
- Outer Core: This layer is in a liquid state. This conclusion is derived from the analysis of earthquake waves, specifically Secondary waves (S-waves). S-waves are shear waves that cannot propagate through liquids. The failure of S-waves to pass through the core (creating a "shadow zone" beyond 103°) confirms that the Outer Core is liquid. The convective flow of molten iron in this layer generates the Earth's magnetic field.
- Inner Core: Despite having higher temperatures than the Outer Core, the Inner Core is solid. This is because the immense pressure at the center of the Earth raises the melting point of the iron-nickel alloy significantly, keeping it in a solid state.
Key Takeaway: The Outer Core is the only internal layer of the Earth that exists in a liquid state, a fact primarily established by the S-wave shadow zone.