1. Composition:
* Oceanic crust: Primarily composed of basalt and gabbro, which are dark-colored, dense, and rich in magnesium and iron.
* Continental crust: Mostly composed of granite and andesite, which are lighter-colored, less dense, and rich in silica, aluminum, and sodium.
2. Density:
* Oceanic crust: More dense (about 2.9 g/cm³) due to its mafic composition.
* Continental crust: Less dense (about 2.7 g/cm³) due to its felsic composition. This difference in density is why oceanic crust subducts beneath continental crust at convergent plate boundaries.
3. Thickness:
* Oceanic crust: Thinner, typically ranging from 5 to 10 kilometers thick.
* Continental crust: Thicker, ranging from 30 to 70 kilometers thick.
4. Age:
* Oceanic crust: Relatively young, generally less than 200 million years old. This is because oceanic crust is constantly being created at mid-ocean ridges and destroyed at subduction zones.
* Continental crust: Much older, with some parts dating back billions of years. Continental crust is less easily destroyed and can be recycled and re-formed over long periods.
