Q50. Consider:
1. The Archaean system is India’s oldest rock system.
2. Gneiss is a common Archaean rock.
3. Dharwar rocks belong to later Archaean sequences.
Which statements are correct?
[HPSC Civil Services Prelims, General Studies (2023)]
- (A) 1 and 2 only
- (B) 1 and 3 only
- (C) All of the above
- (D) 1 only
Answer: (C) All of the above
Explanation: India’s ancient basement includes Archaean granite–gneiss complexes, while Dharwar greenstone and associated metasedimentary sequences represent later stages of early crustal evolution. The examination uses the conventional broad stratigraphic classification that treats all three statements as correct.
Q49. Which statement is correct?
[69th BPSC Preliminary Examination (30 September 2023)]
- (A) Natural gas is found in Dharwar rocks
- (B) Mica is found in Koderma
- (C) Cuddapah series is famous for diamonds
- (D) Petroleum reserves occur in Aravalli Hills
Answer: (B) Mica is found in Koderma
Explanation: Koderma in Jharkhand has long been associated with mica-bearing pegmatites within ancient crystalline terrains. The other alternatives incorrectly pair hydrocarbons or diamond occurrences with geological systems not chiefly recognised for those particular deposits in the question.
Q48. Consider:
I. The Peninsular Plateau formed through breakup and drift of Gondwanaland.
II. It consists mainly of old crystalline, igneous and metamorphic rocks.
Which are correct?
[IB MTS/General (20 December 2023, Shift 1)]
- (A) Only II
- (B) Only I
- (C) Neither I nor II
- (D) Both I and II
Answer: (D) Both I and II
Explanation: The plateau’s basement originated within Gondwana and preserves very old crystalline igneous and metamorphic rocks. Later continental breakup altered India’s position, while local sedimentary basins and basalt eruptions modified but did not replace this ancient foundation.
Q47. Which rock forms during metamorphism?
[SSC MTS (14 September 2023, Shift 1)]
- (A) Slate
- (B) Conglomerate
- (C) Sandstone
- (D) Basalt
Answer: (A) Slate
Explanation: Slate develops when fine-grained sedimentary rocks, commonly shale, are transformed by pressure and heat. Conglomerate and sandstone are sedimentary, while basalt crystallises from lava. These distinctions help classify the many rock units composing India’s geological provinces.
Q46. Which is NOT one of the three principal types of rocks?
[SSC CGL Tier-I (14 July 2023, Shift 3)]
- (A) Igneous rock
- (B) Trace rock
- (C) Metamorphic rock
- (D) Sedimentary rock
Answer: (B) Trace rock
Explanation: The fundamental genetic rock classes are igneous, sedimentary and metamorphic. ‘Trace rock’ is not a recognised fourth category. India’s geology contains examples of all three genuine classes, including Deccan basalt, Gondwana sediments and ancient metamorphic gneiss.
Q45. What was the large supercontinent that existed when the continents were joined roughly 200 million years ago?
[SSC CPO Paper I (4 October 2023, Shift 2)]
- (A) Asia
- (B) India
- (C) Pangaea
- (D) America
Answer: (C) Pangaea
Explanation: Pangaea was the great late Paleozoic–early Mesozoic continental assembly. It later split into northern and southern components, including Gondwana, from which the Indian subcontinent eventually separated before moving toward the Eurasian continental margin.
Q44. Which is an example of a sedimentary rock?
[SSC MTS (16 May 2023, Shift 2; 2022 cycle)]
- (A) Granite
- (B) Marble
- (C) Sandstone
- (D) Basalt
Answer: (C) Sandstone
Explanation: Sandstone forms when sand-sized sediment grains are deposited, compacted and cemented. Granite and basalt crystallise from magma, while marble develops through metamorphism of limestone. Sedimentary sandstones occur widely in India’s Gondwana, Vindhyan and other basins.
Q43. Which is not one of the three main rock categories?
[SSC MTS (2 May 2023, Shift 1; 2022 cycle)]
- (A) Magnetic rocks
- (B) Metamorphic rocks
- (C) Sedimentary rocks
- (D) Igneous rocks
Answer: (A) Magnetic rocks
Explanation: Although rocks may contain magnetic minerals such as magnetite, magnetism does not define a principal genetic rock category. Geologists instead classify rocks as igneous, sedimentary or metamorphic according to their processes of formation and transformation.
Q42. Which is the oldest mountain range in India?
[SSC MTS (16 June 2023, Shift 1; 2022 cycle)]
- (A) Purvanchal Range
- (B) Western Ghats
- (C) Aravalli Range
- (D) Satpura and Vindhya Range
Answer: (C) Aravalli Range
Explanation: Aravalli rocks preserve evidence of very ancient mountain building and have undergone extensive erosion. The Himalayas and Purvanchal belong to much younger tectonic systems, whereas the Aravalli belt is conventionally recognised as India’s oldest mountain range.
Q41. A seismograph is used to record what?
[SSC CGL Tier-I (17 July 2023, Shift 2)]
- (A) Rainfall
- (B) Groundwater level
- (C) Earthquakes
- (D) Underground mineral content
Answer: (C) Earthquakes
Explanation: A seismograph records ground movement produced by seismic waves, enabling analysis of earthquakes and crustal structures. Seismic observations are particularly valuable for understanding India’s active Himalayan collision belt and reactivated faults within the Peninsular Plateau.
