Module 1 - Soil Classification

Question 1

What is the maximum mineral particle diameter in mm which is considered in textural groups?

Answer 1

2

Question 2

Check the soil texture triangle. What texture class is soil with 30% clay and 35% sand?
A) Clay loam
B) Silt loam
C) Loam
D) Clay

Answer 2

A) Clay loam

Question 3

Please match the pairs.
- The soil texture classes were created…
- The Unified Soil Classification System was created…

to describe the agricultural productivity of soils.
to describe soils for geotechnical purposes.

Answer 3

• The soil texture classes were created to describe the agricultural productivity of soils.
• The Unified Soil Classification System was created to describe soils for geotechnical purposes.

Question 4

In the Unified Soil Classification System, what percentage of soils have passed a No 200 sieve to be classified as fine-grained soils?
A) exactly 50%
B) more than 40%
C) more than 50%
D) more than 60%

Answer 4

C) more than 50%

Question 5

____ is the dominating soil order in the Southeastern US!

Answer 5

Ultisol

Question 6

___ is the soil order you would expect in a desert environment.

Answer 6

Aridisol

Question 7

The liquid limit of soil is determined by sieve analysis.
A) True
B) False

Answer 7

A) True

Question 8

The soil water content at the plastic limit is lower than the water content at the liquid limit of the soil.
A) True
B) False

Answer 8

A) True

Question 9

For how many blows is the liquid limit of a soil determined?

Answer 9

25

Question 10

What are the climate-dominated soil types?

Answer 10

Gelisols, Mollisols, Aridisols

Question 11

What are the Time-dominated soil types?

Answer 11

Inceptisols, Alfisols, Spodosols, Ultisols, Oxisols

Question 12

What are the Parent Material soil types?

Answer 12

Andisols, Vertisols

Question 13

Name the US soil taxonomy categories in order (Top down).

Answer 13

Order, Suborder, Great Group, Subgroup, Family, Series

Question 14

What is the nature of differentiating characteristics for the US soil taxonomy category Order?

Answer 14

Presence or absence of major diagnostic horizons, mineralogical properties, and extremes of soil temperature and moisture regimes

Question 15

What is the nature of differentiating characteristics for the US soil taxonomy category Suborder?

Answer 15

Soil moisture regimes and diagnostic horizons

Question 16

What is the nature of differentiating characteristics for the US soil taxonomy category Great Group?

Answer 16

Degree of diagnostic horizon expression within each suborder taxa

Question 17

What is the nature of differentiating characteristics for the US soil taxonomy category Subgroup?

Answer 17

Properties that intergrade to taxa in other order, suborders, and great groups or extra grade to nonsoil material

Question 18

What is the nature of differentiating characteristics for the US soil taxonomy category Family?

Answer 18

Particle-size and mineralogy class of control section, soil temperature regime, and cation exchange activity class in most families; calcareous and reaction, depth, rupture-resistance, coating and crack classes in some families

Question 19

What is the nature of differentiating characteristics for the US soil taxonomy category Series?

Answer 19

Any consistency identifiable soil property not specifically identified as criteria in a higher category. (any soil property considered relevant to potential uses can be recognized as a phase of soil series, i.e., slope, eroded, irrigated, drained, etc.)

Question 20

How many textural classes are there in the USDA scale?

Answer 20

12

Question 21

The USCS distinguishes between coarse-grained soils with more than 50% retained on or above the No.200 (0.075 mm) sieve and fine-grained soils with 50% or more passing the No.200 (0.075 mm) sieve.

Answer 21

True

Question 22

Name the three main features the USCS system is based on.

Answer 22

Percentages of gravel, sand, and fines (fraction passing the No. 200 sieve).

The shape of the grain-size-distribution curve.

Plasticity and compressibility characteristics. In the USCS, the soil is given a descriptive name and a letter symbol indicating its principal characteristics.