Consider the following statements regarding Waves and Tsunamis:

1. Tsunamis can be caused by undersea earthquakes, volcanic eruptions, underwater landslides, or asteroid impacts.

2. Wind-generated ocean waves transfer energy across the water, but water particles themselves do not move forward significantly.

3. The speed of a tsunami decreases as it approaches shallow coastal waters due to the rise in wave height.

4. Unlike regular waves, tsunamis have long wavelengths, which make them almost undetectable in deep oceans.

Which of the above statements are correct?

The correct answer is option 3

Key Points

• Waves vs. Tsunamis
  • Regular waves (Wind-driven)
    • Caused by wind energy transfer.
    • Affect only the surface layer of water.
    • Short wavelengths (a few meters to tens of meters).
    • Water particles move in circular orbits but do not travel forward.
  • Tsunamis (Seismic waves)
    • Triggered by earthquakes, volcanic eruptions, landslides, or asteroid impacts.
    • Affect entire water columns, from the deep ocean to the surface.
    • Extremely long wavelengths (100-500 km).
    • Move at jet-like speeds (500-800 km/h in deep waters) but slow down near coastlines.

Additional Information

• Causes of Tsunamis
  • Tectonic earthquakes – Most tsunamis (80-90%) occur due to seafloor displacement at subduction zones (e.g., 2004 Indian Ocean Tsunami).
  • Underwater volcanic eruptions – Large eruptions displace water rapidly (e.g., Krakatoa 1883).
  • Landslides – Underwater or coastal landslides can generate tsunamis (e.g., Lituya Bay Mega Tsunami, 1958).
  • Asteroid impacts – Extremely rare but capable of producing massive tsunamis (e.g., asteroid impact 66 million years ago linked to dinosaur extinction).
• How Tsunamis Change as They Approach Land:
• Deep Ocean:
  • Speed: 500-800 km/h (like a jet plane).
  • Wave Height: Only a few centimeters to a meter (undetectable).
  • Wavelength: 100-500 km (extremely long).
• Shallow Waters (Near Coast):
  • Speed: Decreases (due to friction with the ocean floor).
  • Wave Height: Rises dramatically (can reach 30 meters or more).
  • Wavelength: Shortens, making waves more noticeable.
• Impact of Tsunamis
  • Massive coastal destruction – Sweeps away buildings, infrastructure, and vegetation.
  • Flooding and saltwater intrusion – Contaminates freshwater supplies.
  • Loss of human life – (e.g., 2004 Indian Ocean tsunami killed 230,000+ people).
  • Economic collapse – Destroyed cities, lost industries, and disrupted fisheries.
  • Environmental impact – Changes coastlines, damages marine ecosystems.
• Notable Tsunamis in History
  • 2004 Indian Ocean Tsunami – 9.1 magnitude earthquake, killed over 230,000 people across multiple countries.
  • 2011 Japan Tsunami (Fukushima Disaster) – 9.0 magnitude earthquake, caused a nuclear meltdown.
  • Krakatoa Tsunami (1883) – Volcanic eruption caused 35-meter waves, killing over 36,000 people.