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How do continental crust and oceanic crust differ in thickness and density?

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Map graphic showing the boundaries of the five oceans-Pacific, Atlantic, Indian, Arctic, and Southern-using color-coded regions. Four different map projections are included: North Pole view, South Pole view, International Date Line view, and Greenwich Meridian view, each displaying the oceans' extents around the continents. — ocean Earth's oceans and their marginal seas cover nearly 71 percent of the planet's surface.

Continental and oceanic crusts differ significantly in both thickness and density, which influences how they sit atop the Earth's mantle.

Density

The continental crust is primarily granitic in composition and has a density of approximately 2.7 grams per cubic cm. In contrast, the oceanic crust is basaltic—richer in iron and magnesium—resulting in a higher density of about 2.9 to 3 grams per cubic cm. Because the continental crust is less dense, it possesses greater buoyancy, allowing it to float higher in the mantle compared to the denser oceanic crust.1

Thickness

There is a marked difference in the vertical extent of these layers:
* Continental Crust: Typically averages about 40 km (25 miles) in thickness, though it can reach 60 to 70 km beneath major mountain ranges and plateaus.12
* Oceanic Crust: Is much thinner, generally averaging only about 6 to 7 km (4 miles) in thickness.12

These variations in density and thickness are fundamental to the two principal elevation levels observed on Earth's surface.1