Consider the following statements: Statement I: In the context of effect of water on rocks, chalk is known as a very permeable rock whereas clay is known as quite an impermeable or least permeable rock. Statement II: Chalk is porous and hence can absorb water. Statement III: Clay is not at all porous. Which one of the following is correct in respect of the above statements?
- A.Both Statement II and Statement III are correct and both of them explain Statement I
- B.Both Statement I and Statement II are correct but only one of them explains Statement I
- C.Only one of the Statements II and III is correct and that explains Statement I
- D.Neither Statement II nor Statement III is correct
▶ Answer & Explanation
Correct answer: C. Only one of the Statements II and III is correct and that explains Statement I
Permeability of a rock refers to the ease with which water can pass through it, determined by the size and interconnectedness of pores. Chalk, being composed of fine-grained calcium carbonate, has numerous small pores, making it porous and permeable, thus allowing water absorption. Clay, on the other hand, consists of very fine particles that pack tightly, forming micropores that are not well-connected, leading to low permeability and impermeability. Therefore, chalk's porosity explains its permeability, while clay's lack of porosity contributes to its impermeability.
Source: UPSC gs1 2025