Some important MCQs related to 12th Geology Exam with Explanations -3

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Unit 1: General Geology

1. Which of the following best describes the Earth's core?
a) Composed mainly of silicate minerals
b) Mostly molten
c) Composed mostly of iron and nickel
d) Part of the Earth's crust
Answer: c) Composed mostly of iron and nickel
Explanation: The Earth's core is primarily composed of iron and nickel, with the outer core being molten and the inner core being solid due to extreme pressure.



2. Which of the following geological features forms when two tectonic plates diverge?
a) Mountain range
b) Oceanic ridge
c) Earthquake
d) Volcanic island
Answer: b) Oceanic ridge
Explanation: When tectonic plates diverge, such as at mid-ocean ridges, magma rises to form new oceanic crust, creating oceanic ridges.


3. Which of the following is NOT a result of tectonic plate movement?
a) Earthquakes
b) Mountain building
c) Volcanic activity
d) Rock weathering
Answer: d) Rock weathering
Explanation: Tectonic plate movements lead to earthquakes, mountain building, and volcanic activity, but rock weathering is a surface process influenced by environmental factors like wind, water, and temperature.

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Unit 2: Petrology

4. Which of the following is a characteristic of basalt?
a) It is an intrusive igneous rock
b) It has a fine-grained texture
c) It is rich in quartz
d) It is light in color
Answer: b) It has a fine-grained texture
Explanation: Basalt is an extrusive igneous rock that forms when lava cools quickly at the Earth's surface, giving it a fine-grained texture.

5. Which rock forms when limestone undergoes metamorphism?
a) Marble
b) Quartzite
c) Slate
d) Schist
Answer: a) Marble
Explanation: Marble is formed by the metamorphism of limestone under high pressure and temperature, leading to the recrystallization of the calcium carbonate in the rock.

6. Which of the following is a type of foliated metamorphic rock?
a) Granite
b) Gabbro
c) Schist
d) Pumice
Answer: c) Schist
Explanation: Schist is a foliated metamorphic rock that exhibits pronounced layering or banding due to the alignment of mineral grains under pressure.


Unit 3: Structural Geology

7. Which geological structure is formed due to compressional forces?
a) Normal fault
b) Reverse fault
c) Strike-slip fault
d) Rift valley
Answer: b) Reverse fault
Explanation: Reverse faults are formed by compressional forces that cause the hanging wall to move up relative to the footwall, often forming mountain ranges.

8. A fault in which the hanging wall moves down relative to the footwall is called a:
a) Normal fault
b) Reverse fault
c) Strike-slip fault
d) Thrust fault
Answer: a) Normal fault
Explanation: Normal faults are caused by extensional forces, where the hanging wall moves downward relative to the footwall.

9. A geologic fold with layers that dip away from the center is called a:
a) Anticline
b) Syncline
c) Monocline
d) Basin
Answer: a) Anticline
Explanation: An anticline is an upward-arching fold in which the oldest layers are at the core and the layers dip away from the center.


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Unit 4: Paleontology

10. Which of the following is an example of a body fossil?
a) Footprint
b) Coprolite
c) Shell
d) Burrow
Answer: c) Shell
Explanation: A body fossil is the actual remains or parts of an organism, such as a shell, whereas trace fossils include footprints, burrows, and coprolites.


11. Which of the following organisms is considered an extinct group of reptiles that lived during the Mesozoic era?
a) Pterosaurs
b) Crocodiles
c) Turtles
d) Lizards
Answer: a) Pterosaurs
Explanation: Pterosaurs were flying reptiles that lived during the Mesozoic era and are considered extinct. They are not dinosaurs, though they lived alongside them.


12. Which of the following fossils is useful for determining the relative age of rocks?
a) Body fossils
b) Trace fossils
c) Index fossils
d) Both a and b
Answer: c) Index fossils
Explanation: Index fossils are used to determine the relative age of rocks because they are widely distributed, and their presence in rocks indicates a specific time period.
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Unit 5: Economic Geology

13. Which mineral is a primary source of zinc?
a) Galena
b) Sphalerite
c) Hematite
d) Chalcopyrite
Answer: b) Sphalerite
Explanation: Sphalerite is the primary ore of zinc, often found in association with other sulfide ores like galena.


14. Which of the following is the main component of natural gas?
a) Methane
b) Ethanol
c) Propane
d) Butane
Answer: a) Methane
Explanation: Methane is the primary component of natural gas, typically forming from the decomposition of organic matter over millions of years.


15. Which of the following is an example of a non-metallic mineral?
a) Iron ore
b) Copper
c) Gypsum
d) Gold
Answer: c) Gypsum
Explanation: Gypsum is a non-metallic mineral used in the manufacture of plaster and wallboard, whereas iron, copper, and gold are metallic minerals.

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