Question
How is the crust different from the mantle in thickness and
density? Which one do we live on?”
density? Which one do we live on?”
Answers
GPT-5 mini
Short answer: the crust is much thinner and less dense than the mantle — and we live on the crust.
Details:
- Thickness
- Crust: very thin relative to the whole Earth. Oceanic crust ≈ 5–10 km thick; continental crust ≈ 30–70 km (thicker under mountains).
- Mantle: about 2,900 km thick (extends from the base of the crust to the core–mantle boundary).
- Density
- Crust: low density, typically ~2.6–2.9 g/cm³ (2,600–2,900 kg/m³) for continental crust; oceanic crust is a bit denser (~2.9–3.0 g/cm³).
- Mantle: higher density, ~3.3 g/cm³ near the top of the mantle increasing to ~5.6 g/cm³ near the core–mantle boundary.
- Composition/behavior (brief)
- Crust: silica-rich rocks (granite on continents, basalt under the oceans), brittle.
- Mantle: ultramafic rocks (peridotite, rich in olivine), mostly solid but ductile and convecting on long timescales.
Which one we live on: the outermost crust (continental crust where we live on land; oceanic crust under the oceans).
Details:
- Thickness
- Crust: very thin relative to the whole Earth. Oceanic crust ≈ 5–10 km thick; continental crust ≈ 30–70 km (thicker under mountains).
- Mantle: about 2,900 km thick (extends from the base of the crust to the core–mantle boundary).
- Density
- Crust: low density, typically ~2.6–2.9 g/cm³ (2,600–2,900 kg/m³) for continental crust; oceanic crust is a bit denser (~2.9–3.0 g/cm³).
- Mantle: higher density, ~3.3 g/cm³ near the top of the mantle increasing to ~5.6 g/cm³ near the core–mantle boundary.
- Composition/behavior (brief)
- Crust: silica-rich rocks (granite on continents, basalt under the oceans), brittle.
- Mantle: ultramafic rocks (peridotite, rich in olivine), mostly solid but ductile and convecting on long timescales.
Which one we live on: the outermost crust (continental crust where we live on land; oceanic crust under the oceans).