Correct Option
The correct option is Differentiation.
Explanation
The "Giant Impact" hypothesis (or Theia Impact) suggests that a Mars-sized body collided with the proto-Earth during the early stages of planetary formation. This event is primarily responsible for the formation of the Moon and had profound effects on Earth's geological evolution.
Detailed Analysis:
- Differentiation (Correct): The immense energy from the Giant Impact melted a significant portion of the Earth. This molten state allowed materials to move freely and separate based on density. Heavier elements like iron and nickel sank to the center to form the Core, while lighter silicate materials rose to form the Mantle and Crust. This density-based separation is known as differentiation.
- Degassing: While the heating and subsequent cooling contributed to the release of gases (degassing) to form the secondary atmosphere, the primary internal geological process facilitated by the melting was differentiation.
- Accretion: Accretion refers to the initial gathering of dust and planetesimals to form the planet, which largely occurred before the Giant Impact.
- Expansion: The Earth did not undergo geological expansion as a process; rather, it compacted and differentiated.
Key Takeaway: The heat generated by the Giant Impact created a magma ocean, which facilitated differentiation, resulting in the Earth's layered structure (Core, Mantle, and Crust).