Soils

Question 1

Times Beach case study

Answer 1

Chemical sprayed on roads to clear dust contained dioxin, a dangerous chemical.

Question 2

Soil

Answer 2

Earth material that has been altered by physical, chemical, and biological processes such that it can support rooted plant life

Question 3

land capability

Answer 3

the suitability of land for a particular use

Question 4

climatic signal

Answer 4

Soils often carry a climatic signal, something that indicates what the past climate was like

Question 5

Weathering

Answer 5

the physical and chemical breakdown of minerals and rocks and the first step in soil development

Question 6

residual soil

Answer 6

Weathered material that remains essentially in place

Question 7

transported soil

Answer 7

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.

Question 8

Soil profile

Answer 8

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.

Question 9

Soil horizons

Answer 9

Layers in soil (A, B, C, etc.) that differ from one another in chemical, physical, and biological properties.

Question 10

O horizon and A horizon

Answer 10

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.

Question 11

E horizon, or zone of leaching

Answer 11

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.

Question 12

B horizon

Answer 12

underlies the O, A, or E horizons and consists of a variety of materials translocated downward from overlying horizons

Question 13

argillic B horizon

Answer 13

An argillic B horizon is enriched in clay minerals that have been translocated downward by soil-forming processes.

Question 14

Bk horizon

Answer 14

characterized by accumulation of calcium carbonate.

Question 15

caliche

Answer 15

irregular accumulation or layers of calcium carbonate in Earth material near the surface

Question 16

C horizon

Answer 16

consists of parent material partially altered by weathering processes

Question 17

R horizon

Answer 17

unaltered parent material composed of consolidated bedrock that underlies the soil

Question 18

texture

Answer 18

depends upon the relative proportions of sand-, silt-, and clay-sized particles

Question 19

Loam

Answer 19

soil composed of sand, silt, and clay sized particles in relatively even (20–40%) concentration

Question 20

Relative profile development

Answer 20

Refers to soils that may be weakly, moderately, or strongly developed, depending on specific soil properties.

Question 21

weakly developed soil profile

Answer 21

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.

Question 22

moderately developed soil profile

Answer 22

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).

Question 23

well-developed soil profile

Answer 23

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.

Question 24

Soil Chronosequence

Answer 24

A series of soils arranged in terms of relative soil profile development from youngest to oldest

Question 25

exposure dating

Answer 25

numerical dating technique

Question 26

Soil fertility

Answer 26

Capacity of a soil to supply nutrients (such as nitrogen, phosphorus, and potassium) needed for plant growth when other factors are favorable.

Question 27

saturated

Answer 27

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.

Question 28

soil taxonomy

Answer 28

comprehensive and systematic classification of soils known as soil taxonomy, which emphasizes the physical and chemical properties of the soil profile

Question 29

unified soil classification system

Answer 29

widely used in engineering practice,

Question 30

Soil strength

Answer 30

ability of a soil to resist deformation

Question 31

Cohesion

Answer 31

measure of the ability of very small silt and clay soil particles to stick together

Question 32

Soil sensitivity

Answer 32

measures changes in soil strength resulting from disturbances such as vibrations or excavations

Question 33

Soil compressibility

Answer 33

easure of a soil’s tendency to consolidate, or decrease in volume.

Question 34

Hydraulic conductivity

Answer 34

sure of the ease with which water moves through a material. . Saturated clean gravels or sands have the highest K values

Question 35

Corrosion

Answer 35

slow weathering or chemical decomposition that proceeds from the surface into the ground

Question 36

Ease of excavation

Answer 36

pertains to the procedures, and hence the equipment, required to remove soils during construction

Question 37

Common excavation

Answer 37

accomplished with an earth mover, a backhoe, or a bulldozer

Question 38

Rippable excavation

Answer 38

requires breaking up the soil with special ripping teeth before it can be removed

Question 39

Blasting or rock cutting

Answer 39

the third, and often the most expensive, category; a hard, silica cemented soil might need to be cut with a jackhammer before being removed.

Question 40

Shrink-swell potential

Answer 40

(soil) Measure of a soil’s tendency to increase and decrease in volume as water content changes.

Question 41

Expansive soil

Answer 41

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

Question 42

Montmorillonite

Answer 42

the common clay mineral associated with most expansive soils

Question 43

Rates of soil erosion

Answer 43

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.

Question 44

The Universal Soil Loss Equation

Answer 44

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

Question 45

Maryland Sediment pollution case study

Answer 45

demonstrated that sediment control measures can reduce sediment pollution in an urbanizing area

Question 46

Sediment pollution

Answer 46

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).

Question 47

Aggrade

Answer 47

When a stream cannot transport sediment effectively and thus fills with it, increasing flood likelihood

Question 48

topsoil

Answer 48

the most fertile soil near the surface that supports vegetation

Question 49

Contour plowing

Answer 49

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

Question 50

No-till agriculture.

Answer 50

No-till agriculture is an integrated plan to plant and harvest crops without plowing while suppressing weeds and other pests.

Question 51

Terracing slopes

Answer 51

Soil erosion on steep slopes can be managed and minimized by terracing slopes to produce flat areas for farming.

Question 52

Planting of more than one crop.

Answer 52

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.

Question 53

desiccation

Answer 53

drying out

Question 54

Soil survey

Answer 54

A survey consisting of a detailed soil map and descriptions of soils and land-use limitations; usually prepared in cooperation with local government.