Question

Arrange the following rocks in increasing grades of metamorphism:
A. Shale,
B. Schist,
C. Gneiss,
D. Phyllite, E. Slate. Choose the correct answer from the options given below:

• A. A, C, D, E, B
• B. B, C, A, D, E
• C. A, E, D, B, C
• D. A, D, C, E, B

Hint:

Metamorphic sequence of shale is Shale \(\rightarrow\) Slate \(\rightarrow\) Phyllite \(\rightarrow\) Schist \(\rightarrow\) Gneiss.

Answer 1

The Correct Option is C

Concept:
Metamorphic grade increases with increasing temperature and pressure. Shale transforms into progressively higher grade metamorphic rocks.

Step 1: Start with parent rock.
Shale is the original sedimentary rock. \[ \text{Lowest}=A \]

Step 2: Low-grade metamorphism.
Shale first changes into slate. \[ \text{Slate}=E \]

Step 3: Next grade.
Slate changes into phyllite. \[ \text{Phyllite}=D \]

Step 4: Higher grade.
Phyllite changes into schist. \[ \text{Schist}=B \]

Step 5: Highest grade among these.
Schist changes into gneiss at still higher metamorphic grade. \[ \text{Highest}=C \] Therefore, increasing grade of metamorphism is: \[ \text{Shale}<\text{Slate}<\text{Phyllite}<\text{Schist}<\text{Gneiss} \] Using letters: \[ A<E<D<B<C \] \[ \therefore \text{Correct Answer is (C)} \]