What are the characteristics of a tsunami generated by an undersea earthquake?

A tsunami generated by an undersea earthquake is characterised by its high speed, long wavelength, and destructive power.

A tsunami is a series of ocean waves with very long wavelengths, typically hundreds of kilometres, caused by large-scale disturbances of the ocean. Undersea earthquakes, which occur due to the movement of tectonic plates, are one of the most common causes of tsunamis. The characteristics of a tsunami generated by an undersea earthquake are largely determined by the magnitude, depth, and location of the earthquake.

One of the key characteristics of a tsunami is its high speed. In deep water, a tsunami can travel at speeds of up to 500 miles (805 kilometres) per hour, similar to a jet plane. This speed is determined by the depth of the water, with tsunamis moving faster in deeper water. As a tsunami approaches the shore and enters shallower water, its speed decreases but its height increases dramatically, often resulting in devastating damage.

Another characteristic of a tsunami is its long wavelength. Unlike normal sea waves, which have a wavelength (the distance between two successive waves) of up to 200 metres, a tsunami can have a wavelength of up to 200 kilometres. This long wavelength means that a tsunami can affect a large area, often impacting entire coastlines rather than just a small area.

The destructive power of a tsunami is another key characteristic. When a tsunami reaches the shore, it can cause massive destruction, often wiping out entire communities. The force of a tsunami is so great that it can move boulders, flip cars, and demolish buildings. The damage caused by a tsunami is not just limited to the immediate impact, but can also include long-term effects such as contamination of drinking water and destruction of infrastructure.

The characteristics of a tsunami can also be influenced by the local geography. For example, a narrow bay can amplify the height of a tsunami, while a steep beach can reduce its destructive power. Therefore, understanding the characteristics of a tsunami and the factors that influence them is crucial for predicting their impact and implementing effective disaster management strategies.