What causes tidal waves (tsunamis) ?

Tsunamis are often commonly called ‘tidal waves’, but this is an inaccurate name as they are not tidal formed.

‘Surface waves’ are formed by action on the surface of the sea, but when a larger, more sudden event occurs under the water, it can disturb a much larger part of the water column.

This sudden displacement of a large amount of water creates a long deep wave known as a Tsunami.

(Thus, these waves are sometimes known as displacement waves, which is an accurate name and explains how they occur in one neat word)

They can be triggered off by many different events; the most destructive and famous causes are underwater earthquakes.

These may occur at thousands of metres in depth, and this displaces a huge amount of water above.

(Thus, they are often also referred to as ‘seismic waves’.)

However, these waves can also be triggered off by other large and sudden events such as nuclear bombs, avalanches and cyclones.

(And even the name we use these days, is not very accurate. This Japanese word translates as “harbour wave”. It was named this because Japanese fisherman would return to a home that had been devastated by a destructive wave that had passed unnoticed underneath them at sea, and seemingly created in the harbour itself.)

(More on tidal waves, their effect and the largest tsunami recorded, in a later ecosystem and page....)