Question

Earth's Physical Layers based on density of each layer?

Answer 1

Do you mean the mechanical (physical) layers of the Earth (lithosphere, asthenosphere, mesosphere, outer core, inner core)? Below they are listed from lowest to highest density with typical density ranges (both g/cm3 and kg/m3) and a short note about each. Densities vary with depth and composition (PREM seismic model gives the detailed depth-dependent values), so the values below are approximate averages.

- Continental crust: ~2.6–2.9 g/cm3 (2600–2900 kg/m3) — silica-rich rocks; thickness ~30–70 km.
- Oceanic crust: ~2.9–3.1 g/cm3 (2900–3100 kg/m3) — denser basaltic crust; thickness ~5–10 km.
- Lithospheric mantle (rigid uppermost mantle, together with crust forms the lithosphere): ~3.3–3.4 g/cm3 (3300–3400 kg/m3).
- Asthenosphere (weak, partially ductile upper mantle beneath the lithosphere): ~3.3–3.5 g/cm3 (3300–3500 kg/m3).
- Transition zone (part of the upper-to-lower mantle; 410–660 km depth): ~3.9–4.1 g/cm3 (3900–4100 kg/m3).
- Lower mantle / mesosphere: ~4.4–5.6 g/cm3 (4400–5600 kg/m3) — denser, solid silicate minerals under high pressure.
- Outer core (liquid, mostly Fe–Ni with light elements): ~9.9–12.2 g/cm3 (9900–12,200 kg/m3).
- Inner core (solid, mainly Fe–Ni alloy): ~12.8–13.1 g/cm3 (12,800–13,100 kg/m3).

Notes:
- Density generally increases with depth because of increasing pressure and compositional changes.
- Mechanical layers (lithosphere/asthenosphere/mesosphere) overlap compositionally with the crust, upper mantle and lower mantle.
- Exact values depend on the seismic model and local variations; the PREM model is a common reference.