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