Different Layers of Soil Horizon

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Different Layers of Soil Horizon

Soil is the mixture of rock debris and organic materials which develop on the earth’s surface. However, whole of the soil is not same and differs in its constituents. In this article, we will discuss about the soil profile and soil horizon, which is an important topic for UPSC IAS exam.

What is soil horizon?

If we dig a pit on land and look at the soil, we find that it consists of six layers which are called horizons. So, soil horizon is basically a distinct layer in the ground.
The six layers of the soil are made up of different substances that either look different, have different chemical makeups, or are physically different from the other layers.

Soil horizon significance

Soil horizons act as the history of the soil in a particular area.
The layers are formed in a specific way due to the original composition of the land, the weather, the vegetation of the area, and other factors.

What are the six layers of the soil?

The six soil horizons are labelled with a letter denotation and are O, A, E, B, C, and R. Each of these soil horizon layers are unique. In the below table, we will discuss about these six horizons of soil in detail.

Horizon	Features
O horizon	It is made up of organic materials or humus. It is the topmost zone of the soil. It is the layer of soil with humus at the surface and decomposed vegetation at the base It is most prominent in forested areas where there is the accumulation of debris fallen from trees.
A horizon	Soil horizon A is the layer that is made up of minerals. This horizon is predominantly the surface layer of many soils in grasslands and agricultural lands.
E horizon	It is a subsurface horizon that has been heavily leached. Anything that can’t be leached out of the soil is left behind and makes up this layer. E horizon if the soil is often found in forests and areas with old soil that hasn’t been disturbed in a long time. This layer is often lighter in color than other layers as much of it has leached into lower layers.
B horizon	B soil horizon is a site of deposition. All of the materials, such as minerals that are leached from the soil horizon A and E, make up this layer in the soil profile. Bulldozers and landscaping can result in erosion that exposes it.
C horizon	Soil Horizon C is the parent material layer. The Earth’s surface deposits created this layer. It could have been produced by glaciers moving across the earth, lake sediment, or the exposure of bedrock. It is the least weathered horizon.
R horizon	Soil horizon R is made up of bedrock. The rocks found in this layer include limestone, quartzite, sandstone, basalt, and granite. This horizon is technically not soil and is usually found under soil horizon C.

Does all soil have all six soil horizons?

No, no necessarily. While some soil profiles may have every single one of the six soil horizons in it, other areas may have fewer soil horizons in their soil compositions.
Majority of soil profiles will have A, B, and C horizons in them. Also, some may also include an O horizon in addition to these three major soil horizons.

Geography notes for UPSC

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