Natural Disasters – Tsunami

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.

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.