soil
Layers
These are the different zones that form due to soil formation processes, such as the decomposition of organic matter, the weathering of rocks, and the action of living organisms.
Scroll down to learn all about each of the 5 soil layers. Make sure to fill in your notes on all 3 pages as you travel down.
Horizon O (surface Layer)
Surface Layer - O
Components: (what is in it): -Decomposing things -leaves -twigs -plant roots -Animal waste Depth: 0-2 inches
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Title
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Horizon A (Topsoil)
Topsoil - A
Composition:- organic matter (dead plants and animals that are breaking down.) -minerals -air -water - partially decomposed waste -small rocks -plant roots -worms & insects
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Title
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Depth: 5-10 inches
Horizon B (Subsoil)
Subsoil - B
Components: -Clay -Iron -medium size rocks toward bottom -dirt/soil -some organic material (leaves, twigs, roots. ect.) Depth: 10-24 inches
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Title
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Horizon C(Weathered Rock)
Weathered Rock -C
Components: -weathered/broken rocks -less organic material -less dirt as you travel down Depth: 24-40 inches
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Title
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Horizon R (Bedrock)
Bedrock - R
Composition: -Solid Rock -Minerals -no dirt or soil Depth: 40 inches or deeper
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Horizon B (Subsoil)
It is a more compact layer, primarily composed of minerals leached from the upper layers (horizons A and E). It may contain accumulations of clays, iron, aluminum, and other compounds. It has a reddish-brown or yellowish color due toiron oxides.
Importance:
⚘ It is less fertile than horizon A, but it can serve as a nutrient reserve. ⚘ It is essential for water storage and anchoring deep roots.
Horizon A(Surface Soil)
It is the layer below the O horizon. It consists of a mixture of organic matter and minerals. It has a dark color due to the presence of humus. It is the most fertile horizon and where the roots of manyplants develop.
Importance:
⚘ It is the most productive layerfor agriculture. ⚘ It houses most of the microorganisms that enrich the soil.
Horizon E (Leaching Zone or Eluviation)
It is a layer that can appear between horizon A and B. It is formed by minerals that have lost nutrients and organic matter due to a leaching process (the transport of soluble substances to deeper layers by water). It has a lighter color compared to theupper layers.
Importance:
⚘ Indicates the mobility of nutrients to deeper horizons. ⚘ Its presence is not always visible inall soils.
These have different physical, chemical, and biological properties, and their study is fundamental in areas such as agriculture, ecology,and geology.
Horizon C (Parent material)
It is composed of fragments of partially decomposed parent rock. It is the base of the soil, and its composition varies depending on the type of original rock (parent rock). It is denser and less chemically altered than the upper layers.
Importance:
⚘ Represents the origin of the soil, as this material forms the upper horizons. ⚘ Over time, it undergoes weathering processes and enriches theupper horizons.
Horizon O (Organic Matter)
It is the topmost layer of soil and is primarily composed of organic matter in various states of decomposition, such as leaves, branches, and animal remains. It may include humus, which is completely decomposed organic matter rich in nutrients.
Importance:
⚘ It is essential for soil fertility and supporting plant life. ⚘ It is where intense biological activity occurs due to microorganisms andsmall animals.
Soil Layers
Frankie Schulte
Created on October 15, 2025
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Transcript
soil
Layers
These are the different zones that form due to soil formation processes, such as the decomposition of organic matter, the weathering of rocks, and the action of living organisms.
Scroll down to learn all about each of the 5 soil layers. Make sure to fill in your notes on all 3 pages as you travel down.
Horizon O (surface Layer)
Surface Layer - O
Components: (what is in it): -Decomposing things -leaves -twigs -plant roots -Animal waste Depth: 0-2 inches
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Title
Write a brief description here
Horizon A (Topsoil)
Topsoil - A
Composition:- organic matter (dead plants and animals that are breaking down.) -minerals -air -water - partially decomposed waste -small rocks -plant roots -worms & insects
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Title
Write a brief description here
Depth: 5-10 inches
Horizon B (Subsoil)
Subsoil - B
Components: -Clay -Iron -medium size rocks toward bottom -dirt/soil -some organic material (leaves, twigs, roots. ect.) Depth: 10-24 inches
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Title
Write a brief description here
Horizon C(Weathered Rock)
Weathered Rock -C
Components: -weathered/broken rocks -less organic material -less dirt as you travel down Depth: 24-40 inches
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Title
Write a brief description here
Horizon R (Bedrock)
Bedrock - R
Composition: -Solid Rock -Minerals -no dirt or soil Depth: 40 inches or deeper
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.
Title
Write a brief description here
Horizon B (Subsoil)
It is a more compact layer, primarily composed of minerals leached from the upper layers (horizons A and E). It may contain accumulations of clays, iron, aluminum, and other compounds. It has a reddish-brown or yellowish color due toiron oxides.
Importance:
⚘ It is less fertile than horizon A, but it can serve as a nutrient reserve. ⚘ It is essential for water storage and anchoring deep roots.
Horizon A(Surface Soil)
It is the layer below the O horizon. It consists of a mixture of organic matter and minerals. It has a dark color due to the presence of humus. It is the most fertile horizon and where the roots of manyplants develop.
Importance:
⚘ It is the most productive layerfor agriculture. ⚘ It houses most of the microorganisms that enrich the soil.
Horizon E (Leaching Zone or Eluviation)
It is a layer that can appear between horizon A and B. It is formed by minerals that have lost nutrients and organic matter due to a leaching process (the transport of soluble substances to deeper layers by water). It has a lighter color compared to theupper layers.
Importance:
⚘ Indicates the mobility of nutrients to deeper horizons. ⚘ Its presence is not always visible inall soils.
These have different physical, chemical, and biological properties, and their study is fundamental in areas such as agriculture, ecology,and geology.
Horizon C (Parent material)
It is composed of fragments of partially decomposed parent rock. It is the base of the soil, and its composition varies depending on the type of original rock (parent rock). It is denser and less chemically altered than the upper layers.
Importance:
⚘ Represents the origin of the soil, as this material forms the upper horizons. ⚘ Over time, it undergoes weathering processes and enriches theupper horizons.
Horizon O (Organic Matter)
It is the topmost layer of soil and is primarily composed of organic matter in various states of decomposition, such as leaves, branches, and animal remains. It may include humus, which is completely decomposed organic matter rich in nutrients.
Importance:
⚘ It is essential for soil fertility and supporting plant life. ⚘ It is where intense biological activity occurs due to microorganisms andsmall animals.