C 水平层是相对未风化的母质土，其它层的矿物都源于此。

Horizon C is relatively unweathered parent material form which the mineral components of the above layers are derived.

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这一连串事件可以解释，为什么过去数十亿年来，所有喷发到地表的火成岩仍然原始而未风化。

This sequence of events would explain why any volcanic rocks that have erupted onto the surface in the past few billion years should still be unweathered and pristine.

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