What is the Difference Between a Tidal Wave and a Tsunami?

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Originally I thought these were the same; and although they are both large ocean waves, they have completely different origins for their energy.

Tidal waves derive their energy from the gravitational pull between the Earth, Sun and Moon and traditionally occur in shallow water and are not nearly or not at all devastating in the same way as Tsunamis.

Unlike today waves, Tsunamis derive their energy from Earth centred events, rather than planetary gravitational interactions. Tsunamis are caused by earthquakes under the sea floor, large landslides that deposit debris into the ocean, or volcanic eruptions that create significant displacements of water – either in the ocean or in large lakes. This displacement travels as a wide, but short in height wave – the actual increase in wave height (amplitude of up to 12 inches) in deep water is negligible, which is why tsunamis can be difficult to detect and predict. The height increase near shore is due to a phenomenon called wave shoaling. As the tsunami reaches shallower water, the wave amplitude must increase in order to compensate for the speed decrease caused by the drag of the ocean floor.

There are tidal waves that resemble tsunami’s but are caused by extreme weather rather than seismic events called meteotsunamis. These waves occur when a low pressure weather system pull a dome of ocean water upwards – generally in a tropical cyclone. Also known as storm surges, these waves are responsible for the majority of casualties during tropical storms. The Coriolis effect which bend currents towards the right in the Northern Hemisphere and to the left in the Southern Hemisphere can intensify storm surges. Strong winds, the shape of the ocean floor, and the narrowness or wideness of the shore area in relation to the surrounding land can all affect the height and severity of meteotsunamis.