Question No. 23: The process that continually adds new crust is
(A) subduction
(B) earthquake
(C) seafloor spreading
(D) convection Correct

Answer: (C) seafloor spreading


Explanation in Simple Sentences:

• Option (A) – Subduction: Subduction is when one tectonic plate slides under another, recycling crust into the mantle. It destroys crust, not adds it. This is incorrect.
• Option (B) – Earthquake: Earthquakes are sudden movements of tectonic plates causing ground shaking. They don’t create new crust. This is incorrect.
• Option (C) – Seafloor spreading: Seafloor spreading happens at mid-ocean ridges where tectonic plates move apart. Magma rises, cools, and forms new oceanic crust. This is correct.
• Option (D) – Convection: Convection is the movement of molten material in the mantle, driving plate tectonics. It supports seafloor spreading but doesn’t directly add crust. This is incorrect.
  

Reason: Seafloor spreading creates new oceanic crust as magma rises at mid-ocean ridges, cools, and solidifies, continually adding to the Earth’s crust. Option (C) is the correct answer.

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Key Terms Explained:

• Crust: The Earth’s outermost solid layer, made of oceanic (thinner, denser) and continental (thicker, less dense) crust.
  
• Seafloor Spreading: A process at mid-ocean ridges where tectonic plates diverge, allowing magma to rise and form new oceanic crust.
  
• Subduction: The process where one tectonic plate is forced under another, sinking into the mantle, recycling crust.
  
• Earthquake: A sudden release of energy in the Earth’s crust, causing ground shaking, often along plate boundaries.
  
• Convection: The circular movement of molten rock in the mantle due to heat, driving tectonic plate movement.
  
• Tectonic Plates: Large, rigid pieces of the Earth’s crust and upper mantle that move and interact, causing geological activity.
  
• Magma: Molten rock beneath the Earth’s surface that forms new crust when it cools during seafloor spreading.
  
• Mid-Ocean Ridge: An underwater mountain range where tectonic plates diverge, and new crust forms via seafloor spreading.

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Five Probable Questions of Similar Difficulty

1. Question: What forms new oceanic crust at mid-ocean ridges?
   (A) Subduction
   (B) Seafloor spreading
   (C) Earthquakes
   (D) Volcanic eruptions
   Answer: (B) Seafloor spreading
   Explanation: Seafloor spreading at mid-ocean ridges allows magma to rise and solidify, forming new oceanic crust.
   
2. Question: Which process recycles Earth’s crust back into the mantle?
   (A) Seafloor spreading
   (B) Convection
   (C) Subduction
   (D) Faulting
   Answer: (C) Subduction
   Explanation: Subduction occurs when a tectonic plate sinks under another, melting into the mantle.
   
3. Question: What drives the movement of tectonic plates?
   (A) Earthquakes
   (B) Magma cooling
   (C) Convection in the mantle
   (D) Crust formation
   Answer: (C) Convection in the mantle
   Explanation: Convection currents in the mantle move tectonic plates, enabling processes like seafloor spreading.
   
4. Question: Where does seafloor spreading primarily occur?
   (A) Continental margins
   (B) Mid-ocean ridges
   (C) Subduction zones
   (D) Fault lines
   Answer: (B) Mid-ocean ridges
   Explanation: Mid-ocean ridges are divergent plate boundaries where new crust forms via seafloor spreading.
   
5. Question: What is a result of seafloor spreading?
   (A) Destruction of crust
   (B) Formation of new crust
   (C) Increased earthquakes only
   (D) Mantle cooling
   Answer: (B) Formation of new crust
   Explanation: Seafloor spreading adds new oceanic crust as magma rises and solidifies at mid-ocean ridges.

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Preparation Strategies for 71st BPSC Prelims

• Study plate tectonics, focusing on seafloor spreading and subduction.
• Learn key terms like crust, magma, and convection.
• Understand the role of mid-ocean ridges in crust formation.
• Practice questions on geological processes and their outcomes.
• Avoid confusing seafloor spreading (creates crust) with subduction (destroys crust).