Final Study Guide - Soil Formation and Classification

Question 1

Soil profile

Answer 1

The vertical arrangement of soil horizons

Question 2

What is a soil pedon?

Answer 2

Basically a clump of soil that has all soil horizons

Question 3

Soil horizon

Answer 3

A layer of soil with distinctive properties

Question 4

What are the 6 master horizons?

Answer 4

O, A, E, B, C, R

Question 5

What are the differences between O and A?

Answer 5

O is mostly organic material, while A is a mix of organic and mineral material

Question 6

What processes form the E horizon?

Answer 6

Minerals leaching out

Question 7

What processes form the B horizon?

Answer 7

Accumulated leaching into the subsoil

Question 8

How are the E and B horizons different?

Answer 8

E is leached of clays, OM, Al, Fe, and other mobile constituents while B is accumulated of materials from above horizons

Question 9

What is the main difference between the C and R horizon?

Answer 9

C is weathered rock while R is solid rock

Question 10

W, M, L, V horizons

Answer 10

W: Water
M: Human-made
L: Biologically produced material deposited in water
V: Dominated by vesicular pores

Question 11

What are the factors of soil formation? Write an equation that shows the relationship between
soil properties and the soil forming factors.

Answer 11

S = f(cl, o, r, p, t)

Soil is the result of climate, organisms, parent material, topography, and time

Question 12

Differentiate among residuum, eolium, alluvium, till, colluvium, and lacustrine materials with
respect to processes

Answer 12

Residuum - formed from residual materials
Eolium, alluvium, till, colluvium, lacustrine - formed from transported materials

Wind - eolium
Water - alluvium, till, lacustrine
Gravity - colluvium

Question 13

Residuum properties of the resulting soil parent material

Answer 13

Residuum: properties depend on hardness, grain size, and composition of rock. Gabbro and basalt are easiest to weather.

Question 14

Eolium properties of the resulting soil parent material

Answer 14

Eolium: deposited by wind, uniform particle size (sandy), weather slowly (made of quartz), tend to be perpetually young

Question 15

Alluvium properties of the resulting soil parent material

Answer 15

Alluvium: deposited by streams and rivers. With layering, the fineness of material depends on how big the floods were.

Big floods: there’d be big particles at the bottom followed by smaller particles higher up (“fining upwards”). Small floods: small bands of fine and loamy soil

Tend to be perpetually young

Also can get strange horizon orders - a C layer can be deposited on top of an A

Question 16

Lacustrine properties of the resulting soil parent material

Answer 16

Lacustrine: layered bands of sediment corresponding to seasons

Question 17

Colluvium properties of the resulting soil parent material

Answer 17

Colluvium: transported by gravity. Typically poorly sorted, creating soils high in rock fragments. Tend to be perpetually young

Question 18

Contrast the properties of basalt and granite and explain why these rocks are different

Answer 18

Basalt is mafic and fine-grained
Granite is large-grained and felsic

Increased grain size = more susceptible to physical weathering
More felsic = more silica content
More mafic = more Fe & Mg content + susceptibility to chemical weathering

Question 19

How do basalt and granite differ from gabbro, andesite, rhyolite, and diorite?

Answer 19

They differ variably based on grain size and how mafic/felsic they are

Question 20

What is aspect in the context of topography?

Answer 20

Aspect is the direction of slope faces

Question 21

What are the five hill slope components? How does water and sediment movement vary
among the five components?

Answer 21

Summit, shoulder, backslope, footslope, toeslope

Question 22

Forest and prairie vegetation have profound effects on the cycling of organic matter and its
distribution in the soil. Discuss these effects in the context of root:shoot ratio for the two
vegetation types

Question 23

On average soils of high latitudes store more organic carbon than do soils in the tropics. Explain why this is the case, taking into consideration biomass production in the two environments

Question 24

How does climate influence soil processes? How are precipitation, temperature, and evapotranspiration relationships depicted in a water budget graph?

Question 25

What is meant by the statement: “Soils are clay factories.”?

Question 26

As soils weather in a well-drained, humid environment, what major properties are expected to change on progressively older landscapes?

Question 27

In an arid environment, how would soil properties compare with those discussed in the question above

Question 28

What is meant by base saturation?

Answer 28

It is the percentage of the cation exchange capacity (CEC) of soil that is occupied by basic cations

Question 29

In highly weathered soils, explain the effects of Al on soil pH, base saturation, plant cation
nutrient supply, and soil phosphate supply

Question 30

How can the effects of Al in soils be overcome?

Question 31

What are the dominant properties of the nine master horizons?

Question 32

What are the main attributes and outcomes of the soil forming processes: melanization,
calcification, podzolization, lessivage, laterization, and gleization?

Question 33

What is meant by Bt, Bk, Bs, Bh, Bqm, Bo, Bw, Bss, Bg?