Natural Disasters-Tsunami

Natural Disasters – Tsunami


  • The name tsunami is derived from the Japanese word meaning harbour wave.
  • Tsunami waves have very long wavelengths and are often caused by a large and sudden displacement of the ocean due to earthquakes, volcanic eruptions etc.
  • They are one of the most destructive natural disasters and can cause dangerous coastal flooding and powerful currents that can last for several hours or days.
  • Tsunami in the open ocean appear in the form of small waves, but grow rapidly in size as they reach shallow water.
  • Tsunamis travel at a high speed in deep waters and slowdown in shallow waters.
  • Tsunamis are not a single wave but come in multiple waves which can take hours to manifest.
  • Run-up is the temporary rise in sea levels when a tsunami reaches the shore.
  • Pacific Ocean is home to 80% of the tsunami waves that occur.

Causes of Tsunami formation


  • Powerful undersea earthquakes are often responsible for the creation of tsunamis.
  • According to Seismologists, only earthquakes that measure greater than 7.0 on the Richter scale have the ability to produce a major tsunami.
  • It should be noted that vertical displacement of the sea floor is the usual cause a tsunami while, horizontal displacement rarely causes tsunamis.
  • One should also remember that all undersea earthquakes do not create tsunamis, as it depends upon the nature and degree of displacement of the seawater columns.


  • Rock fall, landslides, and icefalls etc which can cause the displacement of seawater can also lead to tsunami waves.

Volcanic eruption

  • Underwater volcanic eruption, if powerful enough, can lead to a significant amount of seawater being abruptly displaced.
  • This displacement has the potential of becoming a tsunami wave.

Nuclear Explosion

  • US in 1940 and 1950s generated Tsunami in Marshall Island through testing their nuclear weapons underwater.

Meteorite Impacts

  • Geographical evidences point to a meteorite impact about 5 million years ago which produced a major Tsunami leaving deposits along the Gulf Coast of Mexico and the United States.