2. Earth’s Layers (H)

Earth's Layers Overview The Earth consists of distinct layers classified by composition and mechanical properties:

• Crust: Solid outer layer, composed mainly of Silicon (Si), Oxygen (O), and Aluminum (Al).

• Mantle: Ductile solid beneath the crust, consisting of Silicon (Si), Oxygen (O), and Magnesium (Mg).

• Outer Core: Liquid layer made primarily of Nickel (Ni) and Iron (Fe).

• Inner Core: Solid layer due to high pressure, also made of Nickel (Ni) and Iron (Fe).

Composition: Oxygen (30.0%), Iron (35.0%), Silicon (15.0%), Magnesium (10.0%), Other Elements (10%).

Mechanical Properties:

• Lithosphere: Crust and upper mantle, solid and brittle, broken into tectonic plates.

• Asthenosphere: Upper mantle, ductile solid where tectonic plates float.

Tectonic Plates:

• Continental Crust: Less dense, thicker, mainly granite; oldest parts ~4 billion years.

• Oceanic Crust: More dense, thinner, primarily basalt; recycled and subducts; oldest parts ~200 million years.

In summary, the Earth has distinct layers that define geological processes and tectonic dynamics.