The B horizon is the subsoil layer of a typical soil profile. It lies underneath the topsoil (A horizon) and above the parent material (C horizon). The B horizon is often denser and more compacted than the A horizon, and it may have a different color and texture. It is commonly referred to as the "subsoil" or "B layer".

Some key characteristics of the B horizon include:

1. Subsoil Density: The B horizon is generally more compact and denser than the A horizon due to the accumulation of clay particles and minerals.

2. Clay Accumulation: The B horizon often shows an increase in clay content compared to the A horizon. This is a result of the downward movement of clay particles through the soil profile.

3. Mineral Accumulation: The B horizon can accumulate various minerals, such as iron oxides, aluminum oxides, and calcium carbonate. These accumulations can result in the formation of distinctive soil features like mottles, nodules, or hardpans.

4. Coloration: The B horizon can have a different color from the A horizon, ranging from reddish-brown to yellowish-brown or grayish. The color variations often indicate differences in mineral composition, oxidation-reduction conditions, and soil moisture content.

5. Soil Structure: The B horizon may have a more developed soil structure compared to the A horizon. This structure is influenced by factors like clay content, mineral composition, and the degree of weathering.

6. Less Organic Matter: The B horizon typically contains less organic matter than the A horizon due to the decomposition of organic materials by microorganisms.

The characteristics of the B horizon can vary widely depending on the specific soil type, climate, and geological conditions. It plays an important role in water and nutrient movement within the soil profile, and its properties influence factors such as drainage, root development, and soil fertility.