Earthquake shortens the length of day

Here's an interesting piece of information coming from NASA this week... heres the article from National Geographic Magazine online.

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Saturday's Chile earthquake was so powerful that it likely shifted an Earth axis and shortened the length of a day, NASA announced Monday.

By speeding up Earth's rotation, the magnitude 8.8 earthquake—the fifth strongest ever recorded, according to the USGS—should have shortened an Earth day by 1.26 millionths of a second, according to new computer-model calculations by geophysicist Richard Gross of NASA's Jet Propulsion Laboratory in California.

Just how did the Chile earthquake give Earth a bit of a turbo boost?  Think of it like an ice skater spinning, then pulling his or her arms in.  As he or she pulls their arms in, they start rotating faster.

Likewise, as a portion of Earth's mass drew in ever so slightly and quickly during the Chile earthquake, the planet began spinning a bit quicker.

The Chilean quake was a so-called thrust earthquake, which occurs when a large section of the Earth's surface—in this case, the Nasca tectonic plate—dives beneath an adjacent plate. This process, called subduction, can cause earthquakes and volcanic eruptions (learn about plate tectonics).  The layer of rock on the [Nasca plate] dove down into the Earth's interior, and that's like the skater pulling her arms in toward her body.

Only thrust earthquakes, with their inward motion, can shorten Earth days. Other types of earthquakes, such as horizontal strike-slip quakes, in which two plates slide horizontally past one another, don't affect Earth's rotation.

For more of teh article, click here.