Master Gardener Practice Exam

Understanding soil horizons shows that the C horizon is the zone of partially weathered parent material. It sits beneath the more developed surface horizons and above the bedrock. The material there has begun to break down from the original rock or sediment, but it has not yet undergone the level of alteration that creates the A and B horizons. It often consists of broken rock and partially altered material that will weather further to contribute to the soil above. It’s not organic matter, which belongs to the O horizon; it’s not bedrock, which is the R horizon; and it’s not highly weathered soil, which describes horizons with more intense alteration than the C horizon.