Soil monoliths
A soil monolith is a vertical section of a soil profile preserved in its natural condition (without alterations). The soil section is extracted from the ground without disturbing its conditions and a treatment is carried out in the laboratory to consolidate the soil and to be able to manipulate it.
From the direct observation of the monoliths, details of the morphological properties of the soil can be obtained, such as color, texture, granulometry, structure, biological activity, types of horizons, depth of root activity, action of the fauna that inhabits the soil, human action, presence of inclusions and other properties.
Monolith exhibited at the CISP.
Monoliths become a very valuable tool for knowledge, as material for the study of soils and for the dissemination of the constitution and functions of the edaphic environment, as they allow:
• Study the horizons of a soil.
• Show its main morphological characteristics.
• Understand the main processes and factors of soil formation.
• Facilitate the analysis of the variation between one type of soil and another.
• Deepen knowledge of the soil.
Among the advantages and disadvantages of an exhibition of soil monoliths, it is worth highlighting:
• They are portable.
• They can be used countless times.
• They allow different soil profiles to be easily compared.
• They can be grouped or distributed according to a specific theme.
• They can be observed in closed spaces.
• It is suitable for groups.
• They can be exhibited for long periods.
• They allow temporary and thematic exhibitions.
• They can be exchanged with other institutions to show the diversity of soils in relation to other places.
The soil monoliths exhibited at the Pyrenean Soil Interpretation Centre (CISP) come from soils found in the Pyrenees and Catalan Pre-Pyrenees. The selection of these soils is made based on the soils most present in this area (according to their taxonomic classification) and soils that present a morphology that allows explaining specific edaphic processes, land use problems and other specificities.
It should be noted that a monolith is a soil profile that reflects a specific moment (extraction) in time. In its natural environment, the soil will continue to evolve.
Since soil processes are closely linked to climate and human action, the monoliths are the reference point for this soil in the context of climate change, including its organic carbon content.
Virtual visit to the Pyrenean Soil Interpretation Center (8'57")
Visits to the CISP
High school students.
High school student during a soil workshop.
Process of making a monolith
The making of a monolith is divided into two main phases, extraction and consolidation.
The extraction process includes a previous phase of selecting the locations to extract the samples. To this end, different plots are visited, it is verified that the soil characteristics are those predicted (taking samples with the auger, cleaning slopes, among others), and the technical limitations of extraction are assessed, as well as the ease of access with machinery. Once the extraction permit is obtained from the owner, the specific date can be scheduled.
Different actions in the process of extracting a monolith.
To carry out the extraction, a trench of more than 1 and a half meters deep is made and a prior description of the soil is made (definition of horizons, sampling by the laboratory and field description). Normally, the sample is extracted with a wooden box 150 cm long, 25 cm wide and 10 cm deep. The soil hazard is worked until it is adjusted to the size of the box. Then, the material is extracted from the back, ensuring that the sample remaining inside the box is not damaged. Finally, it is extracted in its entirety, the excess material is removed and it is packaged, ensuring the integrity of the sample during transport.
Diagram of the process of extracting a soil sample for the production of a soil monolith.
The consolidation process begins once the sample is in the laboratory. The process is based on the gradual incorporation and different concentrations of the adhesive product on the upper surface of the sample. Once this consolidation has been completed (this process lasts between 4 and 6 months) the sample is turned and the preparation of the surface of the monolith that will be visible begins. The objective of this phase is to give the monolith an appearance similar to the soil in its natural state. Finally, the sample is attached to the final support of the monolith so that it can be exhibited.
Diagram of the consolidation process for the production of a soil monolith.