Understanding Tsunamis

Revolutionary Worker #1264, January 16, 2005, posted at rwor.org

The insane rantings of Christian fundamentalists in the U.S. claim that the devastating tsunami in the Indian Ocean was god’s punishment of the people of the area for their sins. But the fact is the tsunami was produced by the powerful interaction of a major earthquake and the ocean. It’s a process that can be and has been studied scientifically. And warning systems can be built and deployed to help limit the immense human loss.

Tsunamis are extremely powerful waves usually produced by earthquakes under the seas, when the quake drops or raises the sea floor and an enormous amount of water is suddenly displaced, generating a huge wave. A tsunami in the open ocean can be hundreds of miles from wave crest to wave crest, travelling at speeds up to 500 miles per hour. Sounding a warning that a tsunami is coming is a race against time. And there is also a struggle to figure out how big a particular tsunami is.

In the open ocean surface, the waves of even a very powerful tsunami may be only a few feet high — people on a ship will not even notice them. The immense power of the tsunami comes in part from that fact that the waves go down very deep. Waves on the ocean that people are most familiar with—even if generated by very powerful storms and even if they reach 30 feet high or more —do not penetrate very far into the ocean depths. Tsunamis, on the other hand, reach deep into the ocean. The most advanced tsunami detectors lie on the ocean floor, thousands of feet below the surface, to detect the pressure that only passing tsunamis will create.

Even with the most advanced detectors, it is not always easy to tell whether a tsunami traveling across the ocean will be large or small when it hits the shore. What happens when a tsunami hits is influenced by the shape of the shoreline, undersea canyons, and other factors. When a tsunami approaches land, the wave crests—which might be hundreds of miles apart in the open ocean—get closer and closer together. The wave slows way down but still carries immense power—even tsunami waves only 4 or 5 feet high can pack incredible destructive force when they hit the beach. And usually it’s not the first wave that does the most damage. The first wave hits and then drags trees, pieces of buildings, and cars back into the ocean—and the second and following waves then hit with added destructive power as they carry the wreckage created by the first wave.

Tsunamis are an extremely rapid and powerful natural phenomena, which require urgent analysis and rapid warning systems to limit the loss of life. The principal barrier to doing better at this in today’s world is the global imperialist system.