DNA Explainer: What is a Tsunami and how is it caused?

After a strong earthquake struck southeast of the Loyalty Islands in the Pacific Ocean, New Zealand authorities made a call to its residents along the northern coast to avoid beaches and the shore. The Bureau of Meteorology in Australia also issued a tsunami threat in the offshore territories and islands of the country.

The European Mediterranean Seismological Centre (EMSC) had previously said that the 7.7 magnitude quake's epicentre was 417 km (258 miles) east of Tadine in New Caledonia and that it was at a depth of 10 km (6.2 miles).

It is to be noted that the major earthquake followed at least three other tremors in the region, with magnitudes ranging from 5.7 to 6.1 in a span of just over an hour.

After the tsunami warning, here is all you need to know about what it means and the reasons why a tsunami is caused:

Tsunamis are rare events that refer to rapid rises in the sea level, leading to the generation of giant waves. Tsunamis can travel at a speed of up to 500 miles an hour in the ocean, making them deadly. They can also reach as high as several hundreds of feet when they strike the shore.

Almost two tsunamis are recorded in the world on an average every year but it is only once in about 15 years that the world encounters a destructive tsunami. Most of the tsunamis (as many as 80 per cent of them) are recorded along the Ring of Fire in the Pacific Ocean.

One of the primary reasons behind tsunamis is a major earthquake that can cause movements on the dead floor and transfer its energy to the water above. Some of these earthquakes can cause tsunamis that would spread out everywhere. Otherwise, tsunamis move towards one direction and it depends on the disturbance on the seafloor. They can hit the shore within hours or even minutes.

The Indian Ocean tsunami in 2004 was one of the deadliest tsunamis in recent memory. It killed as many as 2,25,000 people in 14 countries, including Sri Lanka, India, Indonesia, and Thailand.