Mother nature

A lot has been written about the disaster that struck the nations around the rim of the Indian Ocean on December 26th. There are exhaustive articles on the nature of tsunamis in general as well as this particular event. The blogging community of southern Asia has produced a number of riveting first hand accounts of the carnage that have an immediacy lacking from traditional journalism. The three questions that seem to be most commonly asked are "How did this happen?", "What can I do to help?" and "How can anyone prevent this from happening again?".

A tsunami ("tidal wave") is different from the surface waves that continually wash over our beaches. The difference is the mass of water that is being displaced. A surface wave is generated by weather- wind whipping up a relatively small amount of water on the surface of the ocean. Severe storms can generate waves that are very large, even larger then tsunamis when they hit land. But the total mass of water is tiny compared to a tsunami, so their destructive power is limited to the immediate shoreline, where they are quickly dissipated.

On the other hand, a tsunami is caused by a rapid displacement of the floor of the ocean, as is caused by an undersea earthquake. In this situation, the entire mass of the ocean over the site of the displacement is rapidly shifted, causing a disturbance of an immense amount of water. As this disturbance wave travels in the deep ocean, it may not even be noticed by ships at sea- the swell can be only a foot or two high. However, when it moves near land, that same unimaginably huge mass of water is now funneled into a progressively shallower space, resulting in a massive wall of water with the full weight of the ocean behind it. The term "tidal wave" is a misnomer, and its use is discouraged by scientists. Tsunamis have nothing to do with the normal process of tidal ebb and flow.

The most important thing that we can do now, here in the United States, is to send money. There is no practical way of physically helping out, but a massive financial relief effort is crucial. Financial aid is needed not only for immediate assistance, but to prevent the death toll from climbing higher due to disease that frequently follows such massive disasters.

I personally contribute through the Red Cross. This organization took a lot of flak in the aftermath of the 9/11 relief effort, which I felt was extremely unfair. Most people who complained about how their contributions were being spent had very little understanding of the complexities involved in such a massive project. I spent a lot of time working with the Red Cross at the World Trade Center site during those days, and I was extremely impressed with their efficacy, compassion and organization. Furthermore, independant charity scoring agencies (such as the American Institute of Philanthropy and Charity Navigator) have given the Red Cross their highest ratings. There are a number of charities which are helping with this disaster, if you prefer- both the AIP and Charity Navigator Web sites suggest some good ones. But don't wait, the need is real and urgent.

Finally, there is the question of how such a disaster can be prevented in the future. Nothing can obviously be done to prevent earthquakes or the resultant tsunamis. However, unlike quakes that occur on land with little or no warning, tsunamis may travel in the open ocean for several hours before hitting the shore. In the Pacific, where tsunamis are common, many nations participate in the use of early warning systems. The most common approach is an ocean bottom pressure system, which can detect massive shifts of water. Surface buoys transmit the information to shore, and may give inhabitants enough time to evacuate.

The earth tremor itself propigates much more rapidly than the water waves, and can be detected from across the planet quickly. Unfortunately, one cannot always predict whether or not a given undersea quake will give rise to a tsunami, so there would be many false alarms if seismic data alone were used to order evaucations.

One of the reasons why the death toll was so high in December was that tsunamis are extremely uncommon in the Indian ocean. The last such disaster in the Indian ocean was in 1883, after the explosion of the volcano Krakatoa, with 36,000 estimated deaths. In the Pacific, on the other hand, tsunamis occur on a regular basis. The people living around the Pacific rim, especially in Japan, are very concious of this possibility. Several minutes before a tsunami hits land, the sea recedes. Pacific coastal inhabitants might recognize what is coming and immediately head for high ground. In the Indian ocean, on the other hand, this is so rare that some people actually moved down to the shore to investigate the strange phenomenon, putting them directly in harm's way. Apparently some of the nations around the Indian Ocean are now considering the implementation of a Pacific-style tsunami warning system.

Animation from the National Oceanic and Atmospheric Administration