Soils basics Flashcards
Rock vs Soil
basically difference in cohesive forces, rock is source of soil
Two broad soil categories
Residual: (weathering of rock or accum of org materials insitu (dominant in humid or tropic regions) (mechanical or chemical, also biological)
Transported: transported from origin (gravity, wind, water, glaciers, human activity. (dominant in temperate and cold climates) often segregated according to size.
Residual Soil
Insitu formation, weathering of rock or accum or org material insitu. Typical of humid, tropic regions.
- Mechanical (wind,water,ice,tectonic forces)
- Chemical (exposure to: atmos., temp. change, liquid solutions, other materials)
- wide range of sizes, shapes, comp.
- mature at surface decrease until reach parent rock.
- saprolite, soil that includes physical features of the parent rock.
- keep similar structural appearance, cohesion, resist to deform. as parent rock (transported soils do not have this)
- tropics: well drained gives laterite, poor drain give montmorrillonite clays.
- Characteristics of disturbed vs undisturbed soil may vary
Transported Soils
Materials transported from origin. Often segregated by size.
Gravity: short distances
Wind: small particles, aeolian deposits, sand shorter dist., silt clays long dist.. (aeolian silt deposit = loess)
Glacial: glacial drift, deposits = glacial till, moraine (moraine types: end, lateral, recessional); glacial rivers = eskers, kames (dropped along wall, hole), kettle lakes (ice block melt),
Water : River: alluvial deposits - (also glaciofluvial can occur) fines in suspension, coarse in short distance transport, alluvial fans, floodplain deposits, natural levees (river)
Lacustrine (lake), beach, swamp, marsh
Soil gases and liquids
Open pore space/voids, typically include liquid and gas. Often water and air (similar to atmos), but may include other liquids and gases from anthropogenic, natural, biological activity. (hydrocarbon leaks, radioactivity, methane, H2S)
