HILR - Soil Erosion Lesson
Soil Erosion
Dirty Work
So What is Soil?
Soil is the thin layer of material covering the earth’s surface and is formed from the weathering of rocks. It is made up mainly of mineral particles, organic materials, air, water, and living organisms—all of which interact slowly yet constantly.
Most plants get their nutrients from the soil, and they are the primary source of food for humans, animals, and birds. Therefore, most living things on land depend on soil for their existence.
Soil Profile
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Soil is created through the interaction of climate, vegetation, organisms, and topography of the organic and mineral material found on Earth's surface. Soil types vary from place to place because different locations around the world have different climates and topographies and support different kinds of organisms. Each type of soil possesses specific defining characteristics, including color, texture, and mineral composition. As soils develop over time, layers (or horizons) form a soil profile. Most soil profiles cover the earth as 2 main layers – topsoil and subsoil. |
Soil horizons are the layers in the soil as you move down the soil profile. A soil profile may have soil horizons that are easy or difficult to distinguish.
Three Horizons
| Horizon | Description |
A |
A horizon—humus-rich topsoil where nutrient, organic matter and biological activity are highest (i.e. most plant roots, earthworms, insects and micro-organisms are active). The A horizon is usually darker than other horizons because of the organic materials. |
B |
B horizon—clay-rich subsoil. This horizon is often less fertile than the topsoil but holds more moisture. It generally has a lighter color and less biological activity than the A horizon. Texture may be heavier than the A horizon too. |
C |
C horizon—underlying weathered rock (from which the A and B horizons form). |
Some soils also have an O horizon mainly consisting of plant litter which has accumulated on the soil surface.
The properties of horizons are used to distinguish between soils and determine land-use potential.
Soil is a valuable resource that needs to be carefully managed as it is easily damaged, washed or blown away. If we understand soil and manage it properly, we will avoid destroying one of the essential building blocks of our environment and our food security.
Soil Erosion
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Soil erosion is the washing or blowing away (by water or wind) of the top layer of soil or dirt. This was a severe problem in the 1930s during the dust bowl in the Midwest of the United States. Once the soil has eroded, crops do not grow well. Erosion also leaves large sinkholes in the ground, which can weaken buildings and even cause them to collapse. Recently we have seen a rise in human activities and soil erosion. |
Human Activities that Lead to Soil Erosion
Click the tabs below to learn what human activities have contributed to soil erosion.
Soil erosion changes the topography of the land. Changing the topography varies the availability of resources and can decrease biodiversity. Although extreme, soil erosion can lead to desertification. Desertification is the rapidly increasing amount of formerly fertile land turning into desert. The formation of deserts occurs typically due to climatic factors related to latitude and precipitation in a region. Desertification is impacting semi-arid areas because of human activity. Areas susceptible to desertification tend to have sparser vegetation, irregular precipitation patterns. These characteristics in combination with overgrazing, poor agricultural techniques such as over-cultivation, and deforestation have damaged and exposed sensitive soils, leading to further degradation and soil loss. Climate change and extended droughts increase the sensitivity of these areas, as well.
Soil Erosion Challenge
Before You Go, You Need To Know
The following key points are from this explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.
- Understand how soil is made and layers of soil
- Define soil erosion and how it impacts the land
- Common causes of soil erosion and how they affect the environment
- Urbanization
- Mining
- Deforestation
IMAGES CREATED BY GAVS OR OPEN SOURCE