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A generic term for the rocks making up the upper half of the Earth's crust, so called because Silicon and aluminum predominate. Sial is also commonly referred to as "Granitic rock".

Sial sits on top of a denser, "basaltic" layer, called Sima (because silicon and magnesium predominate).

I can't find who originally coined "sial" and "sima", but the terms are frequently associated with Alfred Wegener, as the isostatic balance between Sial and Sima is one of the fundamental parts of his theory of continental drift.

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