Pitara Kids Network

What is a Tsunami?

Last year there were three more fishing villages in the Pacific island country of Papua New Guinea than there are today. You might ask why. The answer is that these three villages were washed away by an ocean wave that was more like a giant wall of water. It goes by the name tsunami, a Japanese term meaning a harbour wave.

Ocean that Becomes a Giant Wall [Illustrations by Kusum Chamoli]

A tsunami is caused by a disturbance in the sea floor, just like the disturbances on land. It may take the form of a quake or volcanic eruption or landslides on the ocean floor. Imagine the slab-like pieces of the sea floor, each of which may be hundreds of kilometres long. And imagine these slabs moving against each other, forcing one or the other upwards.

This upward movement simply pushes the water up. The movement of water is from the deeper parts of the ocean into the shallower parts. And since the shallow parts of the ocean cannot withstand the force of the incoming water, it has only one way to go – and that is up, up and up, creating a huge wave.

Basic types of tsunami

This giant wall of water can reach up to 20 to 30 metres. This ocean wave has the power to come down on land settlements, destroying them immediately. Sometimes tsunamis travel thousands of miles before reaching land. This is what happened to the three fishing villages in Papua New Guinea last year, when a 23 metre wall of water struck them. Almost 6000 people died there and then.