10 Multiple Choice Questions (MCQs) on the topic "Origin and Evolution of the Earth’s Crust" for UPSC preparation.
1. Which theory explains the origin of the Earth from a rotating cloud of gas and dust?
a) Tidal Hypothesis
b) Binary Star Hypothesis
c) Nebular Hypothesis
d) Planetesimal Hypothesis
Answer: c) Nebular Hypothesis
The Nebular Hypothesis, proposed by Immanuel Kant and Laplace, suggests that the Earth formed from a rotating cloud of gas and dust (solar nebula), which contracted under gravity and formed the Sun and planets.
2. According to modern geology, the Earth's crust was primarily formed during which eon?
a) Phanerozoic
b) Proterozoic
c) Hadean
d) Archean
Answer: d) Archean
The Archean Eon (about 4 to 2.5 billion years ago) witnessed the formation of stable continental crusts and the beginning of plate tectonics.
3. The process of differentiation led to the formation of which major Earth layers?
a) Lithosphere and Atmosphere
b) Oceanic and Continental plates
c) Troposphere and Stratosphere
d) Crust, Mantle, and Core
Answer: d) Crust, Mantle, and Core
Differentiation occurred when denser materials like iron sank to form the core, and lighter silicates formed the crust and mantle.
4. Which layer of the Earth is believed to have formed first during planetary differentiation?
a) Crust
b) Mantle
c) Core
d) Lithosphere
Answer: c) Core
Due to gravitational forces, heavy elements like iron and nickel sank to the center, forming the core during the early stages of Earth's formation.
5. Which of the following is the youngest layer in the structure of the Earth?
a) Core
b) Mantle
c) Oceanic Crust
d) Continental Crust
Answer: C. Oceanic Crust
Oceanic crust is geologically younger (generally <200 million years old) due to continuous creation at mid-oceanic ridges, while continental crust can be billions of years old.
6. Which of the following processes is most responsible for the continuous evolution of the Earth’s crust?
a) Radiation
b) Sedimentation
c) Condensation
d) Plate Tectonics
Answer: d)Plate Tectonics
Plate tectonics is a dynamic process causing crustal movements, formation of mountains, oceanic trenches, earthquakes, and volcanic activity, shaping the Earth's crust over time.
7. The earliest rocks on Earth formed approximately how many years ago?
a) 2 billion years ago
b) 4.6 billion years ago
c) 3.8 billion years ago
d) 4.2 billion years ago
Answer: c) 3.8 billion years ago
The oldest rocks discovered are around 3.8 to 4.0 billion years old, from the Archean Eon, and represent the first solidified crust.
8. What was the primary heat source that drove early Earth's internal differentiation?
a) Sunlight
b)Tidal Forces
c) Radioactive Decay
d) Solar Wind
Answer: c) Radioactive Decay
The decay of short-lived radioactive isotopes and gravitational compression provided the heat that melted early Earth, enabling differentiation.
9. The continental crust is primarily composed of which type of rock?
a) Basalt
b) Granite
c) Peridotite
d) Gabbro
Answer: b) Granite
Continental crust is rich in felsic rocks like granite, which are lighter and thinner than basaltic oceanic crust.
10. Which of the following best describes the current scientific view of the Earth's formation?
a) Earth was pulled from the Moon by gravity
b) Earth was formed by volcanic eruptions in space
c) Earth was formed from the collision of black holes
d) Earth formed by accretion of planetesimals in a solar nebula
Answer: d) Earth formed by accretion of planetesimals in a solar nebula
Current understanding suggests Earth formed ~4.6 billion years ago through accretion of dust and rock particles (planetesimals) in the early solar system.
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