< HKDSE Geography < M1 
The various layers of Earth are summed up below:
| Layer (by chemical composition) | Layer (by state) | Maximum depth |
|---|---|---|
| Crust (sial/sima) (1) | Solid lithosphere (4) | 30km |
| Mantle (Fe and Al) (2) | 100km | |
| Plastic asthenosphere (5) | 640km | |
| Solid lower mantle | 2800km | |
| Core (Fe and Ni) (3) | Liquid outer core (6) | 4600km |
| Solid inner core (7) | 6370km |
Crust
The crust is a solid layer on the earth's surface. It includes continental and oceanic crusts.
| Continental | Oceanic | |
| Thickness | Thicker | Thinner |
| Density | Lighter | Denser and heavier |
| Composition | Sial - silica and aluminium | Sima - silica and magnesium |
| Geology | Mainly granitic | Mainly basaltic |
| Remarks | Includes continents and continental shelves | |
Mantle
It is denser, made of aluminium and iron, and divided into three parts.
| Upper mantle | Lower mantle | ||
| Rigid mantle | Asthenopshere | ||
| State | Solid | Liquid | Solid |
| Made of | Rocks | Magma | Rocks |
Core
It is rich in iron and nickel. The outer core is a molten liquid. The inner core is a high-pressure solid.
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