Causes & characteristics of tsunamis

Formation of a Tsunami (Harbour Wave)

Most commonly, tsunamis are formed by an underwater earthquake. An underwater earthquake occurs when the pressure building up between the tectonic plates exceeds the friction which causes the plates to jar suddenly. This causes a large volume of water to be displaced, causing an oscillation which develops at great speed underwater. Sea water will then be retracted from the shoreline in a process known as ‘drawdown’. The displaced water will move at great speeds for example 800km/h in the open sea. However, as the wave approaches land, the coastal configuration will sow down the front of the wave causing it to gain in height as its energy is compressed into a smaller space


Characteristics/Causes of a Tsunami

  • Commonly associated with earthquakes and volcanic eruptions
  • Commonly on destructive margins where the plates are moving towards each other causing a great build-up of pressure
  • Can also be generated by landslides, explosions and more rarely, meteorites
  • Long wavelength whilst in open water
  • Shallow height in open sea e.g. 1m
  • Travel at great speeds e.g. 800km/h
Boxing Day Tsunami 2004

Boxing Day Tsunami 2004

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