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Why the continental crust is composed of granitic rock?

Why the continental crust is composed of granitic rock? And why the oceanic crust is composed of basalt rock? Why not the opposite?

Public Comments

1. the ocean crust is composed of basalt rock because the ocean water has salt in it and i forgot why the continental crust is composed of granite
2. Granite is intrusive, basalt is extrusive. Granite formed and cooled over a long period of time in the crust. Basalt was ejected as magma and cooled much more quickly on the surface.
3. Granite is lighter than basalt. The Earth's crust is really made of basalt. The continental stuff (granite) is lumped together and floating on top like huge debris piles.