Question

2 or 3 key facts about the 4 major layers of the earth

Answer 1

Crust
- Outermost, thinnest layer (oceanic ~5–10 km, continental ~35–70 km).
- Made of solid silicate rocks (basalt in oceanic, granite in continental).
- Hosts life and the tectonic plates whose interactions cause earthquakes and volcanism.

Mantle
- Thickest layer (~2,900 km) of mostly solid silicate rock (peridotite) that behaves plastically over long times.
- Convection in the mantle drives plate motions and mantle plumes.
- Includes the asthenosphere (partially weakened/ductile zone) just below the crust.

Outer core
- Liquid layer (~2,200 km thick) composed mainly of iron and nickel.
- Its convective, electrically conducting fluid generates Earth’s magnetic field (geodynamo).
- S-waves do not travel through it (evidence it is liquid).

Inner core
- Solid sphere (~1,220 km radius) made mostly of iron and nickel.
- Solid despite extreme temperatures because pressures are enormous.
- Very dense; affects seismic wave speeds and contributes to the geomagnetic field dynamics.