When you have a farm, it’s important to understand the difference between residual soil and transported soil. Just as you need to know the properties of clay vs sand, alkaline vs acidic soil, it is also important to understand how soil can be affected by the climate and the weather. Here’s what you need to know.
What You'll Learn Today
What is Residual Soil?
Residual soil is the product of chemical weathering. Its characteristics depend heavily on environmental factors such as the age of the soil, drainage, topography, climate, and the parent material that went into the creation of the soil.
Residual soils occur naturally and are developed from existing material. Usually, they occur when a “parent rock” is weathered over time. The rate at which a soil is weathered depends on a variety of factors, including the climate, soil type, length of exposure, and properties of the parent rock.
You’ll find residual soil all over the world, including Africa, Australia, South America, South Asia, and certain portions of Central America, North America (though generally only in the southeast) and Europe.
These types of soils differ from each other based on the topography of the region along with the climatic patterns and vegetable cover. The composition of the parent rock doesn’t after much.
Residual soils tend to have a mineralogical composition that is very close to the original bedrock and soil grains that are sharp and irregularly-shaped. Rarely are they round. The soil often contains fragments of the parent rock and its thickness varies depending on the extent of the weathering along with the climate, age, and topography.
What is a Transported Soil?
Transported soil, on the other hand, is soil that has been weathered just like residual soil. However, it was transported to a new location by a natural agent like the wind, water, or something else.
Transported soil is a weathered solid deposit that was transported from one place to another by a natural agent like wind, water, or glaciers. It can also be transported by two or more of these agents at once.
There are several key types of transported soils to be aware of – gravity deposited soils, water transported soils, glacier deposited soils, and wind transported soils. Understanding how soil was transported is vital when it comes to knowing its chemical composition and how fertile it might be.
Soil that is carried by water is known as an alluvial deposit. When these deposits are made in a lake, they’re named lacustrine deposits, while in the ocean, they are referred to as marine transported soils.
This is one of the most common ways that soil is transported. Soil particles can be transported by rolling or suspension, with coarse particles being deposited as the velocity of the water decreases.
The wind is another common vector for soil transportation. When soil particles are transported by the wind, this is done by a process known as aeolian depositing.
The size and other characteristics of the particle transported, as is the case with water, depend on the velocity, speed, and direction of the wind. Some extremely large dunes can be created as the result of wind transportation.
Glaciers can carry massive quantities of soil and even boulders as they move. The soil can also be transported large distances.
When soil is made by the movement of a glacier, it is referred to as a drift. Soils that are made by the melting of glaciers are referred to as till.
There is one other type of deposit that can be made by a glacier, and that is a glaciofluvial deposit. These are created by melting water and are often stratified. They are extremely strong.
Some soils can be transported by the sheer influence of gravity alone. Often, this movement is a small distance with soils rolling downhill until they get to their final resting place.
Colluvial soil that is transported by gravity is named talus, often consisting of coarse-grained soil particles and bits of rocks. These soils tend to be in high demand for engineering operations.
If you’re reading this article from an engineer’s perspective (or just want to get a better idea of the difference between residual and transported soils), be sure to take a look at this helpful video:
How is Transported Soil Different From Residual Soil?
The biggest difference between residual soil and transported soil is that transported soil, by its very definition, has to go somewhere. It is somehow moved away from the original location and the original rock from which it was created. Residual soil, on the other hand, stays more or less in the same place.
Because of this, residual soil tends to possess the same characteristics as the parent rock.
While transported soil, like residual soil, can also consist of weathered bits of rock, it has to have been moved by one or more agents.
Transported soil is usually broken into minuscule pieces and the soil tends to be extremely fertile, since it contains a variety of minerals from multiple transported rocks all in one place.
Examples of Residual and Transported Soil
An easy way to differentiate between residual and transported soil is to take a look at some samples.
Residual soil, again, is the product of weathering with the original rock still present to some extent. These soils are usually found in the same general vicinity as the parent rock. A common example is bentonite. This chemically weathered volcanic ash is still found on the parent rock.
Andosol is another example. This, too, develops over volcanic ash and rocky regions. It is rich in metastable halloysite and allophane. Montmorillonite expansive black clay is another kind of residual soil, but this one occurs in poorly drained areas.
Why This Matters
If you have a farm, it’s important to know the difference between residual and transported soil. This will help you fully understand what sorts of properties your soil contains, making it easier for you to identify ideal growing sites and places to raise your livestock.
Transported soils tend to be high in vital minerals, since they often contain particles from multiple areas and types of rock. Which minerals your soil has can vary, however, since no two samples of transported soil are exactly alike.
That’s not to say that residual soil isn’t fertile, though – it all depends on the exact composition of the soil you’re dealing with in a given location.
Consider the key attributes of both types of soil as you plan out your farm landscape design and best uses for the soil you already have moving forward.