The R horizon, also known as the bedrock layer, is the lowest layer of soil in the soil profile. It consists of unweathered rock that has not undergone significant alteration or decomposition. This layer is crucial for understanding soil formation and provides a foundation for the layers above it. In soil science, the R horizon is important for determining soil characteristics and stability. It influences drainage, root penetration, and the overall health of the ecosystem. The presence of the R horizon can vary depending on the geological history of the area and the types of rocks present.