The density of the lithosphere varies, but it's generally considered to be around 2.5 g/cm³ to 3.3 g/cm³.
The lithosphere, Earth's rigid outer layer, comprises the crust and the uppermost part of the mantle. Its density isn't uniform due to the different rock types and compositions found within it.
Density Variations within the Lithosphere
Here's a breakdown of the density variations:
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Crust: The crust, being the outermost layer, is the least dense part of the lithosphere.
- Continental Crust: Primarily composed of granitic rocks rich in silica and aluminum (SIAL), the continental crust typically has a density of around 2.7 g/cm³.
- Oceanic Crust: Mainly composed of basaltic rocks rich in magnesium and iron (SIMA), the oceanic crust is denser than the continental crust, with a density of approximately 3.0 g/cm³.
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Uppermost Mantle: The uppermost part of the mantle that forms the lithosphere is composed of peridotite, an ultramafic rock. This portion is denser than the crust, with a density around 3.3 g/cm³.
Therefore, considering the combination of the crust and the uppermost mantle, the overall density of the lithosphere falls within the range of 2.5 g/cm³ to 3.3 g/cm³. This range accounts for the variations in composition and density between the continental crust, oceanic crust, and the underlying mantle.
While the average density of the entire Earth is about 5.513 g/cm³, this number reflects the much denser core. The lithosphere, being a surface layer, has a significantly lower density.
