Oceanic Crust:
* Density: 2.9 to 3.0 g/cm³ (grams per cubic centimeter)
* Composition: Primarily composed of basalt and gabbro, which are denser mafic rocks rich in magnesium and iron.
Continental Crust:
* Density: 2.7 to 2.8 g/cm³
* Composition: Primarily composed of granite and other felsic rocks, which are less dense and richer in silica, aluminum, and potassium.
Key Differences:
1. Density: Oceanic crust is denser than continental crust due to its mafic composition. This density difference is a primary driver of plate tectonics.
2. Thickness: Oceanic crust is thinner than continental crust, typically ranging from 5 to 10 kilometers thick, while continental crust can be up to 70 kilometers thick.
Impact on Plate Tectonics:
* Subduction: The higher density of oceanic crust causes it to subduct (sink) beneath the less dense continental crust at convergent plate boundaries.
* Isostasy: The principle of isostasy states that the Earth's crust "floats" on the denser mantle. The density difference between oceanic and continental crust contributes to the varying elevations of these landforms.
In summary: Oceanic crust is denser than continental crust due to its composition of denser mafic rocks. This density difference is a key factor in the movement and interaction of Earth's tectonic plates.
