April 27, 2011

Part of celebrating the Earth this month is recognizing its awesome power. I have written many books about natural events like tornadoes, earthquakes, tsunamis, wildfires, and many other natural occurrences that we humans classify as "disasters" for ourselves. 

A reader named Emily A. wrote last week to ask what the record is for the longest earthquake. I responded by asking her to do some research and tell us what she found out (once a teacher, always a teacher, I guess).

Emily came back with the correct answer.

Location:                    Sumatra
Date:                          December 26, 2004
Size:                          9.1-9.3
How long it lasted:      10 minutes

  This is the longest (and third strongest) earthquake that was ever recorded on a seismograph.

It was an undersea earthquake that is also known as the 2004 Indian Ocean earthquake. Like the one that happened recently in Japan, it set off a series of devastating tsunamis up to 100 feet (30 meters) high all along the coast of the Indian Ocean, killing more than 225,000 people in eleven countries. Indonesia, Sri Lanka, India, and Thailand were hardest hit. The Sumatra Earthquake happened along the Pacific "Ring of Fire," where 81% of the world’s earthquakes occur. This famous photograph is of the tsunami striking Ao Nang, Thailand.

It is difficult to measure exactly how long an earthquake lasts, because the tremors start gradually and when the big shaking stops, the actual tremor is still dying down. But, scientists think this lasted anywhere from 8½ to 10 minutes, which is very long. As a comparison, the big Northridge Earthquake that occurred in California in 1994 lasted just 15 seconds.

The Sumatra Earthquake was one of the deadliest natural disasters in history.
With a magnitude of between 9.1 and 9.3, it is the second largest earthquake ever recorded on a seismograph. 

Here is an interesting photograph, to show just how much the earth shifted during this massive quake. Some islands (like the one pictured here) grew as they were lifted above the water line, while others tipped over and partially submerged as they dropped back into the water. This island doubled in size during the quake. The land surrounding the green area was all underwater before the earthquake happened.

If you are interested in learning more about this record-breaking earthquake, Cal Tech has a website with more information, animations and graphics to explain what happened when this massive earthquake tore the earth apart across a fault break that was longer than the entire state of California.


Tsunami Photograph: David Rydevik

Island Photograph: Kerry Sieh, TO


What are you doing this Earth Month to contribute to the global effort to pledge a Billion Acts of Green? Click on "Comments," at the bottom of any Earth Day story, and tell me how you are making a difference. We will continue to accept your ideas through Thursday, April 28. Then, on Friday 4/29, we will publish all your comments in one big article, to honor each writer’s promise to protect our planet, and inspire other readers to do the same.


Posted by: Seymour Simon

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