The B horizon is the subsoil layer beneath the A horizon and above the C horizon. In Earth Science, it is where minerals like clay, iron, and nutrients often accumulate after being leached from above.
The B horizon is the subsoil layer in a soil profile, sitting below the A horizon and above the C horizon. In Earth Science, this is the zone where materials washed down from the layers above collect, especially clay, iron, aluminum, and dissolved nutrients.
That downward movement is called leaching. Rainwater moves through the upper soil, carrying fine particles and minerals with it. Some of those materials stay behind in the B horizon instead of reaching deeper rock or sediment, so the layer often becomes denser, darker, or more reddish than the topsoil depending on what has accumulated there.
The B horizon is not usually the richest layer for roots and organic matter, but it still matters a lot. Its texture is often more compact than the A horizon because of the clay content, which changes how water moves through the ground. Water may pass more slowly through this layer, or it may pool above it if the B horizon is especially dense.
That makes the B horizon part of the soil's filter system. As water moves through it, some nutrients are stored and some are held on mineral surfaces instead of washing away. This is why the B horizon can support plant growth indirectly, even though most visible organic life is concentrated higher up in the soil profile.
Its exact look depends on climate, parent material, and how much time the soil has had to develop. In a wet climate with a lot of leaching, the B horizon may be thick and strongly developed. In a younger or drier soil, it may be thin, weak, or barely separated from the layers around it.
The B horizon matters because it shows you what happened to a soil over time. If you know where minerals are accumulating, you can infer how water has moved through the ground, how much weathering has happened, and whether the soil is likely to hold nutrients or drain well.
In Earth Science, that is useful for reading soil profiles in diagrams and field samples. A thick, clay-rich B horizon often points to long-term soil development and strong leaching. A thin or poorly developed B horizon can suggest younger soil, drier conditions, or limited movement of material through the ground.
It also connects directly to plant growth and land use. Farmers, gardeners, and environmental scientists care about whether a soil holds water, drains too fast, or stores nutrients in a layer roots can eventually reach. The B horizon can affect all of those conditions by changing permeability and nutrient retention.
This term also helps you connect soil to bigger Earth systems. Soil is not just broken rock, it is a layered product of climate, organisms, topography, parent material, and time. The B horizon is one of the clearest places where those soil-forming factors leave visible evidence.
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Visual cheatsheet
view galleryA Horizon
The A horizon sits above the B horizon and is usually the topsoil layer with more organic matter, roots, and biological activity. If the A horizon is where a lot of mixing and life happen, the B horizon is where some of the washed-down minerals and clay collect. Comparing the two helps you see how soil materials move downward through a profile.
C Horizon
The C horizon is below the B horizon and is closer to the parent material, so it is less altered by soil-forming processes. The B horizon often acts like the transition zone between surface soil and the less-weathered material beneath it. In a soil profile diagram, the difference between B and C shows how far weathering and leaching have gone.
Soil Profile
A soil profile is the full vertical section of soil, and the B horizon is one of its main layers. When you study a profile, you are looking for changes in color, texture, and composition from horizon to horizon. The B horizon is especially useful because it often shows accumulation that reveals how the soil developed.
Nutrient Retention
The B horizon affects nutrient retention because clay and minerals can hold onto certain nutrients instead of letting them wash away. That makes the layer part of the soil's storage system. In class, you may connect this idea to why some soils stay fertile longer than others and why drainage and composition matter for agriculture.
A quiz or lab question might show you a soil profile diagram and ask you to identify the B horizon from its position and texture. You may need to explain why it is denser than the A horizon, or predict how water moves through it after rainfall. In a short response, you could describe leaching, mineral accumulation, and the effect on nutrient storage.
If your class does field observations, you may also use the term when describing soil samples by color, clay content, or drainage. A good answer is not just "the middle layer." It connects the layer to what is happening in the soil system, especially the movement of dissolved minerals from top to bottom.
The A horizon is topsoil, with more organic matter, roots, and biological activity near the surface. The B horizon is subsoil, where minerals and clay often accumulate after leaching from above. If you remember that A is usually darker and richer in humus while B is denser and more mineral-rich, the difference becomes much easier to spot in soil diagrams.
The B horizon is the subsoil layer in a soil profile, found below the A horizon and above the C horizon.
It is known for accumulating clay, iron, and other minerals that are washed down from upper layers by leaching.
A B horizon is often denser than topsoil, which changes how water drains and how roots move through the soil.
Its thickness, color, and texture can tell you a lot about climate, soil age, and how much weathering has happened.
In Earth Science, the B horizon is a clue to soil formation, nutrient storage, and how the ground will behave for plants and water.
The B horizon is the subsoil layer beneath the A horizon and above the C horizon. It is where minerals and clay often build up after being carried downward from the topsoil. In Earth Science, you use it to read how a soil formed and how water has moved through it.
It is often denser because it contains more clay and mineral material and less loose organic matter than the A horizon. That tighter texture slows water movement and can make the layer feel more compact. Density can vary by soil type, climate, and how much leaching has happened.
The A horizon is the upper soil layer with more humus, roots, and biological activity. The B horizon is lower down and usually has less organic matter but more accumulated minerals. If you are looking at a profile, A is the active topsoil and B is the subsoil where material collects.
Look for the layer below the darker topsoil that often has a different color, more clay, and a more compact texture. It may appear reddish, brown, or yellowish depending on the minerals present. In a diagram or lab sample, its position and texture are usually the biggest clues.