How do scientists measure the thickness of Earth's crust?
Quick Answer
They use seismic waves, gravity data, and receiver functions to estimate where the crust ends and the mantle begins. The crust is about 5–10 km thick under oceans and roughly 30–70 km under continents.
The Full Story
The thickness of Earth's crust varies widely, so scientists combine several methods to measure it. Seismic waves change speed at the crust-mantle boundary, known as the Moho, allowing geophysicists to estimate depth from earthquakes or controlled-source surveys. Gravity measurements also help because thick crust and different rock densities slightly alter Earth's gravitational field. Under oceans the crust is much thinner, typically about 5 to 10 kilometers, while beneath continents it is often around 30 to 70 kilometers thick and even thicker beneath major mountain belts. These measurements help reveal plate structure and continental roots.
Key Facts
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Suggested video title for this topic:
"Earth’s crust is thinner than you think—here’s how we measure it."
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