Final answer:
The Loess Hills are composed of several layers, with the key ones being the O horizon (organic layer), the A horizon (topsoil), and the B horizon (subsoil). Each plays a significant role in the region's ecosystem and soil characteristics.
Step-by-step explanation:
The Loess Hills, which are geological formations composed of wind-blown silt, contain several layers that are key to their structure. Specifically, the physical properties of the soil in this region can be broken down into various horizons. For the purpose of identifying the main layers as it pertains to soil, the composition is as follows:
Soil Horizons
The O horizon or organic layer, which consists of freshly decomposing organic matter - humus - at the surface, with decomposed vegetation at the base, and is crucial for enriching the soil with nutrients and enhancing moisture retention.
The A horizon, also known as the topsoil, is the layer beneath the O horizon, composed of a mixture of organic material with inorganic products of weathering; it is dark in color due to the presence of organic matter and is vital for plant production.
The B horizon or subsoil, situated below the A horizon, is a dense layer where fine material from above has accumulated; it may contain nodules or a layer of calcium carbonate.
These horizons make up the primary vertical structure of the Loess Hills' soil, with each layer playing a specific role in the ecosystem and soil characteristics of the region.