风化壳是地表上不连续的原岩原地的残积物堆积层。上是土状碎屑，往下碎屑颗粒增加，粒度变大，再往下为岩石碎块至完整岩石，这是风化壳剖面分层。风化壳是地表岩石经水、气、生物等物理、化学作用（风化作用）后残留形成。原岩中易风化、易流失的矿物、化学成分被风化流失，而耐风化、难流失的矿物、成分就残留，如花岗岩中的黑云母、长石可能先风化为碎屑、土，而耐风化的石英就残留。九华山风化壳是花岗岩风化后残留的碎屑与石英颗粒组成的碎屑堆积层，是植被生长与水分保持的基础物质。 Weathered Crust Weathered crust is a discontinuous layer of autochthonous debris from weathered protolith. The its upper layer is earthy debris and the down one contains more and larger granular debris, and further down, debris materials are more rock fragments until to the whole rock, that is weathered crust profile. The weathered crust results from physical and chemical weathering of water, air, creatures and so on. Those  protolith’s minerals and chemical compositions weak against the weathering, like biotite and feldspar in granite, are easily weathered and lost; while those strong against weathering, like quartz, will be residuum to being main composition of debris. The Jiuhuashan weathered crust of granite mainly consists of quartz granules and debris, which are basic substance for plant growth and water conservation.