The stratification of the soil is the way in which sediments accumulate soil over each other in layers. Soil formation is a process that takes millions of years, and in that time hundreds of thousands of layers of different materials have accumulated.
Rock or layered soils are made up of visible layers of sediment, which can be a few millimeters to several hundred meters thick. They are made up of a wide variety of shapes and materials.
Strata can be made up of layers of earth, other living beings, gases, water, mineral salts, lava, stone or volcanic fragments deposited one on top of the other.
Soil stratification can be seen with the naked eye in some places, such as ancient river beds. That stratification is so old that it has been transformed into rock.
Sedimentary rock formed with layers of sediment over time. These layers of sediment create the pattern of visible bands or strata. These strata show the geological history of the environment in which the rock formed.
For example, if there is a layer of clay followed by a layer of limestone, it is known that the environment was once a muddy environment before turning into a lake or something similar.
Causes of soil stratification
The layers or strata are visible due to the result of changes in the texture or composition of the material during its deposit.
This exposure of the layers may also be due to the pauses produced in the deposition of the different materials, or to changes in their composition or temperature before the newer layers covered them.
Another cause of the particular shape that the profiles take, especially in river channels, is the composition in particles, some finer and others thicker. The different colors originate from the different mineral compositions.
Water and wind also intervene, carrying out a work of homogenizing the particles that they drag, classifying them according to their size, weight and shape. This gives shape to the layering.
Characteristics of the profiles and horizons
The strata are called “horizons” and the set of layers is called “profile . “
Each profile is made up of at least four horizons, listed below from top to bottom:
1- Washing horizon
Exposed to erosion and washing away by rain, it is composed of porous organic matter , living organisms and minerals.
It is also made up of remains of leaves and branches, humus and fungi. In addition, it has some inorganic elements and its color is brownish.
At a deeper level it contains clays, iron oxides, and moist organic matter.
2- Precipitation horizon
It has clays and has reddish tones due to its ferric compounds. It also contains traces of altered rock and organic material from the first profile.
3- Subsoil horizon
It is made up of rocky material fragmented in different proportions, subjected to processes of weathering or decomposition of the rock into smaller parts, physically or chemically.
4- Mother rock or original horizon
It is a rocky material on which the soil is supported. It is composed of inorganic elements of volcanic and sedimentary origins and grains of petrological origin.
It remains practically unaltered, or without significant alterations, over time.
- Ryan Hultzman. (2017). Stratification: Definition, Theory & Examples. 09/30/2017, from Study.com Website: study.com
- The Editors of Encyclopædia Britannica. (2017). Stratification. 09/30/2017, from Encyclopædia Britannica Website: britannica.com
- Editors. (2017). Stratification. 09/30/2017, Science and Biology Website: Cienciaybiologia.com
- IUSS Working Group WRB, 2015. World Reference Base for Soil Resources 2014, Update 2015. International Soil Classification System for Soil Nomenclature and the Creation of Soil Map Legends. Reports on World Soil Resources 106. FAO, Rome.
- Editor. (2017). Sedimentary Structures. 10/03/2017, from Indiana Edu Website: indiana.edu