Nepedia
Back to Discover
Advanced Reader
🌍

Soil classification

earth science Maturity 5-7 Next article →

Soil classification is the systematic method of grouping soils based on specific characteristics. Scientists and engineers use these groups to understand how soil behaves. This process helps people decide how to use land effectively. It also helps with planning infrastructure like roads and buildings. Classification systems use measurable traits like texture and mineral composition. They also look at the process of soil formation. By using these frameworks, researchers can compare different regions of the world.

Soil profile
Soil profile

One way to look at soil is as a material for engineering. Geotechnical engineers classify soil to see if it can support foundations. They need to know if the ground is stable for building. The Unified Soil Classification System, or USCS, is common in North America. This system uses three major groups to organize soil. The first group is coarse-grained soils, such as sand and gravel. The second group is fine-grained soils, which include silt and clay. The third group is highly organic soil, also called peat.

SoilTextureTriangle
SoilTextureTriangle

Engineers further divide these groups to get more precise details. In the USCS, sands and gravels are separated by grain size. They are labeled as either "well-graded" or "poorly-graded." Silts and clays are categorized using Atterberg limits. These limits help engineers identify high-plasticity or low-plasticity soils. Plasticity refers to how much a soil deforms when wet. Moderately organic soils are also distinguished by how their properties change when they dry. Other systems like the AASHTO system help with pavement construction.

Core sample
Core sample

Soil science takes a different approach by looking at soil as a resource. This often involves a natural system approach. This means grouping soils by their intrinsic morphology or their genesis. Genesis refers to how the soil was originally formed. The USDA soil taxonomy is a major system used in this field. It uses taxonomic criteria and laboratory tests to create hierarchical classes. These classes help scientists understand the history of the land.

Global soils map USDA
Global soils map USDA

The USDA soil taxonomy organizes soils into several levels. These levels include orders, suborders, great groups, subgroups, and families. There are twelve recognized soil orders in the United States. Each order reflects specific processes like climate and vegetation. Understanding these orders helps managers predict how soil will behave. This is vital for agriculture and conservation efforts. In Canada, researchers are studying the Leptosolic order. These are soils that are very shallow over bedrock.

Bodenart
Bodenart

History shows that humans have always categorized soil. Ancient inscriptions at the temple of Horus at Edfu show soil use. These helped determine where to build temples. Ancient Greek scholars also created classifications based on soil qualities. In the United States, Guy Donald Smith helped develop the USDA taxonomy. He was the director of the soil survey investigations. Today, we use modern tools like SoilGrids for automated mapping. This system uses models to create global maps at high resolution.

Trial pit
Trial pit

Classification is also a critical tool for workplace safety. The U.S. Occupational Safety and Health Administration, or OSHA, uses soil types to protect workers. They classify soil in excavations and trenches to prevent collapses. They look at the unconfined compressive strength of the soil. Stable rock can be excavated with vertical sides. Type A soils are cohesive and have high strength. Type B soils are also cohesive but have lower strength. Type C soils are granular or very weak.

Standard penetration test
Standard penetration test

Safety classifications are different from scientific taxonomy. OSHA focuses on stability and the risk of trench failure. They consider moisture content and vibrations from nearby equipment. They also look for the presence of fissures in the ground. These factors change how much pressure the soil exerts. Proper identification helps decide if workers need protective sloping or shoring. This ensures that the ground remains stable during construction. Understanding these different systems helps us manage the earth safely.

629 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (24)
File:SoilTextureTriangle.svg
SoilTextureTriangle.svg
File:Cone penetration test.svg
Cone penetration test.svg
File:Core sample.svg
Core sample.svg
File:Geo-electrical sounding.svg
Geo-electrical sounding.svg
File:In situ permeameter test.svg
In situ permeameter test.svg
File:Inclinometer.svg
Inclinometer.svg
File:Load test.svg
Load test.svg
File:Pore pressure measurement.svg
Pore pressure measurement.svg
File:Ram sounding.svg
Ram sounding.svg
File:Rock control drilling.svg
Rock control drilling.svg
File:Rotary pressure sounding.svg
Rotary pressure sounding.svg
File:Rotary weight sounding.svg
Rotary weight sounding.svg

+ 12 more

More to explore

🔗 What's this?

Concepts mentioned in this article

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.