The provided reference does not state that there are 4 layers of crust, instead, it describes four layers of the Earth: crust, mantle, outer core, and inner core. Therefore, based on the reference, there is 1 crust layer, not 4. The Earth is structured with these 4 layers:
| Layer | Description |
|---|---|
| Crust | The outermost layer, where we live and walk. |
| Mantle | Located directly below the crust. |
| Outer Core | Situated beneath the mantle. |
| Inner Core | The deepest and most central layer of Earth. |
The reference defines the Earth's structure, not the crust's specific layers. Thus, there's only one layer that can be defined as the "crust."
