The Deadly 2004 Tsunami

 

Many of us remember the 2004 tsunami. It was the deadliest in history, killing 230,000 people. My mate David was in Kuala Lumpur, Malaysia, at the time and he told me KL was not affected. However we both went to Penang soon after and found out that 50 people had died there on a single beach.

A tsunami happens when a very large volume of water is suddenly displaced. This can happen at the boundary between two tectonic plates when one plate suddenly slips under, or over the other. In the 2004 tsunami case, the epicentre was somewhere near the Northern tip Sumatra, on the West side. This creates a circular wave in the water, a bit like when you throw a stone in a pond. Only much bigger and faster. The odd thing is that in open water, the wave is hardly noticeable with a height of less than 1 m. But it moves at a frightening speed, like 500 to 1000 km/h, and hardly loses any energy. That’s why the 2004 beast killed people all the way to the East coast of Africa. When it reaches shallower waters, the speed reduces to something like 70km/h but the height can get up to 40 or 50 meters.

A tsunami is stopped by land. Kuala Lumpur was shielded by Sumatra. But it can also be refracted. That is how some of the wave went around the tip of Sumatra and managed to hit Penang, which is close to the Thai border.

References

Wikipedia

http://geodesy.unr.edu/hanspeterplag/library/projects/eseas_white/Tsunami.htm

2004 Tsunami

https://www.earthmagazine.org/article/benchmarks-december-26-2004-indian-ocean-tsunami-strikes/