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Airdate: Jan 11, 2001
Scientist: Geoff Chester

The Moon: Earthquakes

The Moon: Earthquakes
The gravitational pull of the moon causes our tides to rise and fall, and scientists think that it may have an influence on earthquake activity as well.

Transcript:
The Moon - Earthquakes

Ambience: earthquake

It's well known that the gravitational pull of the moon causes our tides to rise and fall, but scientists think that the moon may have an influence on earthquake activity as well. I'm Jim Metzner, and this is the Pulse of the Planet. We're listening to a time lapse recording of an earthquake.

Chester: One of the more subtle effects of the moon is the action that it has on the surface of the earth.

Geoff Chester is an astronomer and public affairs officer at the U.S. Naval Observatory.

Chester: One of the things that you'll notice if you look through a copy of the Old Farmer's Almanac is the moon rides high or the moon rides low. That tells you when the moon is highest and lowest in the sky at a particular month. And these are times, especially around the times of new moon or full moon, when it's possible that there might be a greater triggering mechanism for earthquakes. Because the moon has a tidal pull on the the solid surface of the earth just as much as it has an effect on the liquid surface of the earth. You can actually measure the tidal influence on land during the course of a day; it goes up and down a few centimeters every day, depending on where the moon is in the sky and where we are on the tide cycle.

Another little-known effect of the moon is that it may be slowing us down.

Chester: The moon is actually slowing the earth's rotation down. It actually slows us at a rate of about 2 thousandths of a second per day per century. So a day now takes about 2 thousandths of a second longer to complete than it did in 1900.

According to Geoff Chester, at this current rate of slowing, 3 million years from now, a day will be about 1 minute longer than it is now. To hear about our new CD, please visit our website at pulseplanet.com. Pulse of the Planet is made possible by the National Science Foundation. I'm Jim Metzner.