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The Day The Earth Shook

14 Mar 11
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We love the kids’ school. Among other things, even their field trips are about learning. Back in the U.S. the 5th grade class gets an afternoon field trip to an amusement park. Elana’s 5th grade class here and their teachers spent three days by themselves living in a village where they planted rice, made straw hats and washed a water buffalo.

At the Bandung International School, all students from grades 6 through 11 must participate in the school’s outreach program. This program teaches independence, along with various life skills depending on the trip – kids going to the southern coast of Java learn first aid and water safety, while another trip introduces students to community service. Adam had to go on one of the trips, so he chose traveling to the Gili Islands off the coast of Lombok to become certified as a scuba diver.

At the time it seemed like a good idea. He gains independence and self-confidence while learning a sport that will stay with him the rest of his life. But then the Japanese Earthquake hit on Friday, March 11th, his last day of diving, triggering a massive tsunami that has killed thousands in coastal Japan. Suddenly, having our son on a small, remote island with no high ground to run to struck me as foolish.

In the end he was fine. While the quake registered at 6.2 on the Gilis, some 3665 miles from Tokyo, two major islands lie between the Gilis and the earthquake’s epicenter, preventing the waves from reaching them. In fact, the teachers accompanying the students on the trip seemed a little disappointed that the tsunami at most increased wave action by a few centimeters. But we had a few tense hours before we were certain that things were going to be okay.

Not so, of course, for the people of Japan.

The quake was the most powerful temblor to hit that country since they first began to keep such records in the early 1800s. The epicenter was located some 15 miles beneath the sea floor (making it a shallow quake, which is more destructive) some 76 miles east of Japan’s Honshu Island and the city of Sandei.

This entire region has a difficult relationship with the earth. The very same process that brought such devastation, as understood through plate tectonics, also helped to create the islands that make up Japan, Indonesia, and many other countries here.

The epicenter was also 165 miles west of the Japan Trench. This trench is the boundary between the heavy Pacific Plate and the lighter (in relative terms of course) Eurasian Plate.

Because the Pacific Plate is heavier, it slides under the Eurasian plate. But this is not a smooth process. Imagine two pieces of felt sliding next to each other. The movement will be jerky as parts of the felt stick to each other. Well, it’s a similar process for the plates. They catch on each other, stopping for a moment the plate’s movement. But the energy pushing them to move continues, eventually forcing the plate to slip. It could take many years for this to happen, but eventually it will. It is this “slippage” and release of the built-up energy that led to the Japanese earthquake.

This same slippage also displaces water. This is what caused the tsunami.

Quakes here are often powerful because of the wide area over which the plates can stick. The greater the area that is stuck, the greater the level of energy that is built up, so the larger the earthquake when that energy is eventually released.

The science lesson of tectonics has always fascinated me, but it means a lot more when your child’s future rests on a slip of plates and a fortunate line of geography.


Adam with a very mellow cuttlefish

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