Earth and Space Science / Unit 3: Plate Tectonics
3.1 Earth's Layers by Composition
Notes
Earth has three main layers based on chemical makeup.
- Crust: thin, rocky outer layer. Continental crust (about 30-70 km thick, granite-like) and oceanic crust (about 5-10 km thick, basalt, denser).
- Mantle: thick layer of hot silicate rock, about 2,900 km thick and 80% of Earth's volume.
- Core: mostly iron and nickel. Radius about 3,500 km.
- Density increases with depth: the core is the densest layer.
- Scientists learn about the interior mostly from seismic waves, since no one can drill that deep.
Practice
Which layer makes up most of Earth's volume?
The mantle is about 80% of the volume.
Compared with continental crust, oceanic crust is:
Oceanic crust is basalt, thin and dense.
The core is mostly made of:
Evidence includes seismic data and meteorites.
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