MCQ Detailed View

The correct answer is Sea floor deformation and vertical water displacement.

A tsunami is a series of large ocean waves typically caused by the sudden displacement of a large volume of water. The most common trigger is an undersea earthquake, especially those occurring in subduction zones where one tectonic plate moves beneath another. When the sea floor is uplifted or depressed abruptly, the overlying water column is displaced vertically. This movement generates powerful waves that travel across the ocean at high speeds.

Tsunamis can also result from underwater volcanic eruptions, landslides, or even the collapse of glaciers into the sea. However, earthquakes remain the leading cause of most destructive tsunamis recorded in history. Unlike ordinary wind-generated waves, tsunamis carry enormous amounts of energy because the entire water column is disturbed from the ocean surface down to the seabed.

When tsunamis travel across deep oceans, they may go unnoticed because their wave height is often less than a meter, but their speed can exceed 700 km/h (about the speed of a jet plane). As they approach shallow coastal waters, the waves slow down, but their height increases dramatically, often leading to catastrophic flooding and destruction.

The 2004 Indian Ocean Tsunami, triggered by a massive earthquake near Sumatra, is a tragic example. It killed more than 230,000 people across several countries, highlighting the devastating power of sea floor deformation.

🔑 Key Facts:

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  Tsunamis are caused by vertical displacement of water due to sea floor movement.

  
  


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  Major triggers: undersea earthquakes, volcanic eruptions, and landslides.

  
  


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  Travel speed: up to 700–800 km/h in deep ocean.

  
  


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  Become destructive when waves amplify near coastlines.

  
  


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  Not caused by tides, moon’s pull, or seasonal winds.

  
  

👉 Final Answer: The main cause of a tsunami is sea floor deformation and vertical water displacement.