Tsunami' is a Japanese word meaning destructive waves'.
→ When an earthquake of an intensity of 7 or more occurs on the sea floor or due to a volcanic explosion in the ocean or by a large scale land slide, large, powerful and extraordinarily long waves take place on the surface of the ocean. These are called 'Tsunami'.
→ Mostly the tsunami originates due to an earthquake at the sea floor. That is why the tsunamis are also called as oceanic earthquake waves.
→ When an earthquake takes place in the ocean, its impact is less near the focus of the earthquake. But these waves become very destructive as they reach the coast. By the time these waves approach the coasts, their height sometimes is more than 30 metres.
→ Tsunami waves reach towards the coast in a sequence one after another. When these waves pass through the shallow sea, they turn more devastating.
→ Its velocity is reduce near the coast but the height increases. So these waves surge ahead in the form of a wall and cause severe devastation.
→India on 26th December, 2004 and Japan on 11th March, 2011 experienced very devastating disasters of tsunami.