1. Which of the following best explains the origin of Earth's crust according to the Nebular Hypothesis?
a) The crust was formed through the collision of stars.
b) The crust condensed from a rotating cloud of gas and dust.
c) The crust emerged from oceanic evaporation.
d) The crust was ejected from the moon.
Answer: b) The crust condensed from a rotating cloud of gas and dust.
Explanation: The Nebular Hypothesis suggests that the solar system, including Earth, formed from a nebula—a rotating cloud of gas and dust. As it condensed under gravity, Earth formed with layers, eventually developing a crust.
2. Which era is known for the initial solidification of the Earth's crust?
a) Hadean
b) Proterozoic
c) Paleozoic
d) Mesozoic
Answer: a) Hadean
Explanation: The Hadean Eon (about 4.6 to 4.0 billion years ago) marks the period when the Earth began to cool and its crust started to solidify.
3. The differentiation of the Earth's layers into crust, mantle, and core was primarily due to:
a) Wind erosion
b) Glacial movements
c) Ocean currents
d) Radioactive decay and density differences
Answer: d) Radioactive decay and density differences
Explanation: Heat from radioactive decay caused partial melting. Denser materials sank to form the core, while lighter silicates rose to form the crust.
4. The continental crust is primarily composed of:
a) Basalt
b) Peridotite
c) Iron-nickel alloy
d) Granite
Answer: c) Granite
Explanation: The continental crust is felsic in nature, mainly made of granite, which is less dense than the mafic (basaltic) oceanic crust.
5. The oldest known rocks on Earth are found in:
a) Arawali Range
b) Canadian Shield
c) Andes
d) Western Ghats
Answer: b) Canadian Shield
Explanation: The Canadian Shield contains rocks as old as 4 billion years, making it one of the most ancient parts of Earth’s crust.
6. Which of the following is NOT a theory associated with the origin of Earth's crust?
a) Plate Tectonics Theory
b) Continental Drift Theory
c) Seafloor Spreading Theory
d) Big Bang Theory
Answer: d) Big Bang Theory
Explanation: The Big Bang Theory explains the origin of the universe, not the Earth’s crust. The other three are directly involved in explaining crustal evolution.
7. The process of subduction is crucial in the evolution of the Earth's crust because:
a) It leads to the creation of river systems.
b) It results in the weathering of rocks.
c) It produces ozone in the atmosphere.
d)It causes the recycling of oceanic crust into the mantle.
Answer: d) It causes the recycling of oceanic crust into the mantle.
Explanation: Subduction zones are areas where denser oceanic crust sinks beneath continental crust, recycling material and shaping crustal structure.
8. Which process is most responsible for the formation of oceanic crust at mid-ocean ridges?
a) Subduction
b) Erosion
c) Sea-floor spreading
d) Folding
Answer: c) Sea-floor spreading
Explanation: Magma rises at mid-ocean ridges and solidifies, creating new oceanic crust—a key mechanism of sea-floor spreading.
9. The initial crust of the Earth was likely:
a) Continental and felsic
b) Oceanic and mafic
c) Metallic and ductile
d) Carbon-rich and soft
Answer: b) Oceanic and mafic
Explanation: The earliest crust was mafic (basaltic), denser, and formed from the rapid cooling of magma. Continental (felsic) crust evolved later.
10. Which of the following statements about the evolution of Earth's crust is INCORRECT?
a) Continental crust is older than oceanic crust.
b) Oceanic crust is continuously formed and destroyed.
c) Earth’s crust has remained unchanged since its formation.
d) Plate tectonics contributes to crustal evolution.
Answer: c) Earth’s crust has remained unchanged since its formation.
Explanation: The Earth’s crust is dynamic, constantly being formed, modified, and recycled through tectonic activity and erosion.
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