Soils Flashcards
Times Beach case study
Chemical sprayed on roads to clear dust contained dioxin, a dangerous chemical.
Soil
Earth material that has been altered by physical, chemical, and biological processes such that it can support rooted plant life
land capability
the suitability of land for a particular use
climatic signal
Soils often carry a climatic signal, something that indicates what the past climate was like
Weathering
the physical and chemical breakdown of minerals and rocks and the first step in soil development
residual soil
Weathered material that remains essentially in place
transported soil
Eroded rock particles that are transported by water, wind, or glaciers and then modified in their new deposition location form. The fertile soils formed on glacial deposits in the midwestern United States are transported soils.
Soil profile
Weathering of earth materials that, along with biological activity and time, produces a soil that contains several horizons distinct from the parent material from which the soil formed.
Soil horizons
Layers in soil (A, B, C, etc.) that differ from one another in chemical, physical, and biological properties.
O horizon and A horizon
contain highly concentrated organic material, such as decomposing plants. The differences between these two layers reflect the amount of organic material present in each. In general, the O horizon consists almost entirely of plant litter and other organic material, whereas the underlying A horizon contains a good deal of both organic and mineral material.
E horizon, or zone of leaching
light-colored layer that is leached of iron-bearing components. This horizon is light in color because it contains less organic material than the O and A horizons and little inorganic coloring material, such as iron oxides.
B horizon
underlies the O, A, or E horizons and consists of a variety of materials translocated downward from overlying horizons
argillic B horizon
An argillic B horizon is enriched in clay minerals that have been translocated downward by soil-forming processes.
Bk horizon
characterized by accumulation of calcium carbonate.
caliche
irregular accumulation or layers of calcium carbonate in Earth material near the surface
C horizon
consists of parent material partially altered by weathering processes
R horizon
unaltered parent material composed of consolidated bedrock that underlies the soil
texture
depends upon the relative proportions of sand-, silt-, and clay-sized particles
Loam
soil composed of sand, silt, and clay sized particles in relatively even (20–40%) concentration
Relative profile development
Refers to soils that may be weakly, moderately, or strongly developed, depending on specific soil properties.
weakly developed soil profile
generally characterized by an A horizon directly over a C horizon (with no B horizon or one that is very weakly developed). The C horizon may be oxidized. Such soils tend to be only a few hundred years old in most areas, but they may be several thousand years old in others.
moderately developed soil profile
consist of an A horizon overlying an argillic Bt horizon that overlies the C horizon. A carbonate Bk horizon may also be present but is not necessary for a soil to be considered moderately developed. These soils have a B horizon with translocated changes, a better-developed texture, and redder colors than those that are weakly developed. Moderately developed soils often date from at least the Pleistocene (i.e., are more than 10,000 years old).
well-developed soil profile
characterized by redder colors in the Bt horizon, more translocation of clay to the Bt horizon, and stronger structure. A K horizon may also be present but is not necessary for a soil to be considered strongly developed. Well-developed soils vary widely in age, with typical ranges between 40,000 and several hundred thousand years and older.
Soil Chronosequence
A series of soils arranged in terms of relative soil profile development from youngest to oldest
exposure dating
numerical dating technique
Soil fertility
Capacity of a soil to supply nutrients (such as nitrogen, phosphorus, and potassium) needed for plant growth when other factors are favorable.
saturated
If all the pore spaces in a block of soil are completely filled with water, the soil is said to be in a saturated condition; otherwise, it is said to be unsaturated.
soil taxonomy
comprehensive and systematic classification of soils known as soil taxonomy, which emphasizes the physical and chemical properties of the soil profile
unified soil classification system
widely used in engineering practice,
Soil strength
ability of a soil to resist deformation
Cohesion
measure of the ability of very small silt and clay soil particles to stick together
Soil sensitivity
measures changes in soil strength resulting from disturbances such as vibrations or excavations
Soil compressibility
easure of a soil’s tendency to consolidate, or decrease in volume.
Hydraulic conductivity
sure of the ease with which water moves through a material. . Saturated clean gravels or sands have the highest K values
Corrosion
slow weathering or chemical decomposition that proceeds from the surface into the ground
Ease of excavation
pertains to the procedures, and hence the equipment, required to remove soils during construction
Common excavation
accomplished with an earth mover, a backhoe, or a bulldozer
Rippable excavation
requires breaking up the soil with special ripping teeth before it can be removed
Blasting or rock cutting
the third, and often the most expensive, category; a hard, silica cemented soil might need to be cut with a jackhammer before being removed.
Shrink-swell potential
(soil) Measure of a soil’s tendency to increase and decrease in volume as water content changes.
Expansive soil
With respect to engineering properties of soils, refers to soils that, upon wetting and drying, will alternately expand and contract, causing problems for foundations of buildings and other structures
Montmorillonite
the common clay mineral associated with most expansive soils
Rates of soil erosion
measured as a volume, mass, or weight of soil that is removed from a location within a specified time and area, such as kilograms per year per hectare.
The Universal Soil Loss Equation
A = RELSCP
where
A = long-term average annual soil loss for the site being considered
R = long-term rainfall runoff erosion factor
E = soil erodibility index
L = hillslope/length factor
S = hillslope/gradient, or slope factor
C = soil cover factor
P = erosion-control practice factor
Maryland Sediment pollution case study
demonstrated that sediment control measures can reduce sediment pollution in an urbanizing area
Sediment pollution
Pollution of some part of the environment either on land or in a body of water by sediment that has been transported into that environment by wind or water; an example is turbidity of a water supply (muddy water).
Aggrade
When a stream cannot transport sediment effectively and thus fills with it, increasing flood likelihood
topsoil
the most fertile soil near the surface that supports vegetation
Contour plowing
This involves plowing with the natural topography of the land. Furrows are plowed perpendicular to the slope of the land rather than in the downslope direction. This is one of the most effective ways to reduce erosion by running water and is widely used
No-till agriculture.
No-till agriculture is an integrated plan to plant and harvest crops without plowing while suppressing weeds and other pests.
Terracing slopes
Soil erosion on steep slopes can be managed and minimized by terracing slopes to produce flat areas for farming.
Planting of more than one crop.
This method is most effective on small farms in the tropical rain forest and other areas. The forest trees are cut in small patches of land, and some smaller trees and plants are left in place. Several crops are planted among the remaining natural vegetation After several years, the land is allowed to recover. When the forest has grown back, the process may be repeated. This approach works if human population on the land is low. With increased population and pressure to farm more land more frequently, the practice is not sustainable.
desiccation
drying out
Soil survey
A survey consisting of a detailed soil map and descriptions of soils and land-use limitations; usually prepared in cooperation with local government.
