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.

youdao

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.

youdao

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.

youdao