I’ve noticed that plowed fields and dirt roads that trucks take tend to have the stickiest mud. Is it some churning action, in which air is mixed in, that causes this?
In: Physics
It all depends on the content of “fines” in the soil. Fines are soil particles smaller than sand and are silts and clays. The higher the content of silt and clay in the soil, the more cohesive it will be. There are specific types of clays that are more cohesive than others, but in general, all clay will become “sticky” when wet.
This mostly comes down to the composition of the soil. Water likes to stick to itself and some materials. Certain materials that stick well to water can cause it to become sort of a weak form of cement, and if the ground is unable to drain away the water, more accumulates at the surface. Soils that are rich in fresher organic matter which absorbs and retains water better and/or clay, which is very fine particles, tend to be dense when wet and get a denser mud. You’re likely to find lots of the former in fields because that type of soil is great for growing most of our common crops, and you tend to find lots of fine sand, silt, dust, and clay in well traveled dirt roads because small grain sizes make for a smoother road, and the weight of the vehicles packs and crushes it even further. Dirt roads because of how packed down there are don’t drain very well so any water that can’t easily run off stays there.
Dirt is basically dead plants that have turned into Soil. They have different properties than clay and silt, sand, etc. different forms of mud can possess different characteristics depending on what the mud is made of. Is it primarily sand? Primarily Soil from decaying plant matter? Is it primarily clay? So that’s mostly why some mud might look different.
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