Q104 / 270 · NDA 2026 (Phase 1) · General Ability
Consider the following statements regarding the Earth's crust:
I. The continental crust is thinner under fold mountains.
II. The mean thickness of ocean crust is $30\,\text{km}$.
III. The Earth's crust is brittle in nature.
Which of the statements given above is/are correct?
I. The continental crust is thinner under fold mountains.
II. The mean thickness of ocean crust is $30\,\text{km}$.
III. The Earth's crust is brittle in nature.
Which of the statements given above is/are correct?
- AI only
- BI and II
- Correct answerCIII only
- DI and III
Solution
Statement I is incorrect. The continental crust is thicker in the areas of major mountain systems. For example, it is about $70\,\text{km}$ thick in the Himalayan region.
Statement II is incorrect. The mean thickness of the oceanic crust is about $5\,\text{km}$, whereas that of the continental crust is around $30\,\text{km}$.
Statement III is correct. The Earth's crust is the outermost solid part of the Earth and is brittle in nature, meaning it is prone to fracturing and faulting under stress.
Therefore, only statement III is correct.
Answer: III only
Statement II is incorrect. The mean thickness of the oceanic crust is about $5\,\text{km}$, whereas that of the continental crust is around $30\,\text{km}$.
Statement III is correct. The Earth's crust is the outermost solid part of the Earth and is brittle in nature, meaning it is prone to fracturing and faulting under stress.
Therefore, only statement III is correct.
Answer: III only
Hence, the correct answer is option: 'C'.