What is tsunami? What causes it? How are tsunami waves different from sea waves? Can it be predicted?

Tsunami waves have hit the Pacific Region islands from Japan to Russia to Hawaii Island to New Zealand, causing devastation on the coasts of the islands dotting the Pacific Ocean Rim. The alarm bells for a tsunami were set ringing after a strong earthquake measuring 8.8 on the Richter Scale struck Kamchatka, the Far Eastern region of Russia. With this, the moot question that has cropped up is, what is a tsunami? How does a tsunami originate? Why and how does it become devastating? 

What is tsunami?

Tsunami is a Japanese language word that can be translated as 'harbor wave.' It is a series of waves caused by the displacement of a large volume of water, generally in the ocean or a large lake. The tsunami waves are different from ocean waves. While the ocean waves are caused by wind or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event. So, what displaces a large volume of water? Tsunamis can be triggered by earthquakes, volcanic eruptions, and underwater explosions, including detonations, landslides, glacier calvings, meteorite impacts, and other disturbances above or below water.

How different are tsunami waves?

The tsunami waves are completely different from the sea waves, which appear as breaking waves. A tsunami wave may instead initially resemble a rapidly rising tide. Tsunamis are made up of a series of waves, with periods ranging from minutes to hours. These waves arrive in a so-called "wave train," which has heights of tens of metres. Ancient Greek historian Thucydides was the first to suggest in the 5th century BC in his book 'History of the Peloponnesian War' that tsunamis were related to 'submarine earthquakes.' A tsunami was recorded for the first time in 479 BC, when it occurred in the Greek colony of Potidaea and was caused by an earthquake. 

Can tsunamis be predicted?

A tsunami cannot be predicted precisely even if the magnitude and the epicenter of an earthquake are known. As geologists, oceanographers, and seismologists study each earthquake by analyzing factors, they can issue a tsunami warning. However, an automated system can provide warnings immediately after an earthquake is noticed. This system uses bottom pressure sensors, attached to buoys, which monitor the pressure of the overlying water column.