Earth’s crust is very thin compared to the whole planet: it is about 5–10 km thick under the oceans and roughly 30–70 km thick under the continents, with typical averages of about 7 km (oceanic) and 35–40 km (continental).

Quick Scoop

  • Under most oceans, the crust is only about 5–10 km thick, forming dense, basalt-rich oceanic crust.
  • Under continents, the crust thickens to around 30–70 km, with some mountain regions reaching 70–80 km of continental crust.
  • On average, taking both types together, Earth’s crust is roughly 15–20 km thick if you “blend” oceanic and continental areas.

Oceanic vs continental

  • Oceanic crust:
    • Typical thickness: ~7 km on average.
* Composition: denser, mafic rocks like basalt and gabbro.
  • Continental crust:
    • Typical thickness: ~35–40 km on average, ranging roughly 25–70 km, and up to ~80 km beneath large mountain belts.
* Composition: lighter, more felsic rocks such as granite.

A thin “skin” on Earth

  • Compared with Earth’s diameter of about 12,742 km, even the thickest crust (around 70–80 km) is like a thin skin , similar to the skin on an apple relative to the fruit.
  • The crust makes up less than 1% of Earth’s volume; below it lies the much thicker mantle, about 2,900–3,000 km deep.

TL;DR: Earth’s crust is about 5–10 km thick under oceans and 30–70 km thick under continents, averaging roughly 15–20 km overall.

Information gathered from public forums or data available on the internet and portrayed here.