| environ. |
soil layer Distinctive successive layers of soil produced by internal redistribution processes. Conventionally the layers have been divided into A, B and C horizons. The A horizon is the upper layer, containing humus and is leached and/or eluviated of many minerals. The B horizon forms a zone of deposition and is enriched with clay minerals and iron/aluminium oxides from the A layer. The C layer is the parent material for the present soil and may be partially weathered rock, transported glacial or alluvial material or an earlier soil (由内部的再分配过程所产生的独特的连续层土壤。传统的土壤层被分为A，B，C三层。A层是最上层，含有腐殖质，被浸出和/或多种矿物质淋溶。B层形成沉淀区，富含粘土矿物和来自A层的铁/铝氧化物。C层是当前土壤的母质，部分可能是风化岩，运输冰川或冲积土材料或者是更早的土壤。) |
