Which of the following statements is/are true for Loess? i. It is predominantly a silt-sized sediment that is formed by the accumulation of wind-blown dust ii. It is usually homogenous iii. It is non-porous
- AOnly (i)
- BOnly (i) and (ii)Correct
- COnly (ii) and (iii)
- D(i), (ii) and (iii)
Solution
Concept
Physical properties and characteristics of loess
Formula
NONE
Step-by-step solution
1. Loess is an aeolian deposit consisting predominantly of silt-sized particles deposited by wind. 2. It exhibits high uniformity and homogeneity throughout its deposit layer. 3. Loess is highly porous and prone to collapsible behavior when saturated, making statement iii false. Answer: B
Explanation
Loess is an aeolian soil deposit composed mainly of wind-blown, silt-sized particles that form uniform, homogenous soil layers. However, loess deposits are characterized by high porosity and macro-pore structure that can collapse when saturated. Because statements i and ii are correct while statement iii is false, option B is the correct answer.
Why the other options are wrong
A) Statement (ii) is also true as loess deposits are characteristically homogeneous in nature. C) Statement (i) is true and statement (iii) is false because loess is highly porous. D) Statement (iii) is false because loess has high porosity and an open pore structure.
Shortcut
Loess is wind-blown (eolian) silt that is homogeneous, but highly porous (not non-porous).
Common mistake
Selecting option D by assuming loess is non-porous, failing to recognize that it is a highly porous sediment.
Correct answer: B) Only (i) and (ii)