How The Chilean Quake Moved An Entire Planet

  • Chilean troops and firefighters unload relief supplies Wednesday from a military helicopter in the coastal town of Dichato, which was heavily damaged by tsunami waves produced by Saturday's 8.8-magnitude earthquake.
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    Chilean troops and firefighters unload relief supplies Wednesday from a military helicopter in the coastal town of Dichato, which was heavily damaged by tsunami waves produced by Saturday's 8.8-magnitude earthquake.
    Ricardo Mazalan/AP
  • A policeman stands near medicine and other items donated Wednesday for earthquake victims.
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    A policeman stands near medicine and other items donated Wednesday for earthquake victims.
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  • A woman washes her hands at a makeshift shelter for displaced people in the seaside town of Constitucion on Tuesday.
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    A woman washes her hands at a makeshift shelter for displaced people in the seaside town of Constitucion on Tuesday.
    Fernando Vergara/AP
  • Secretary of State Hillary Clinton is greeted by Chilean President Michelle Bachelet at the airport in the capital, Santiago, on Tuesday.
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    Secretary of State Hillary Clinton is greeted by Chilean President Michelle Bachelet at the airport in the capital, Santiago, on Tuesday.
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  • Chilean army armored personnel carriers drive along a bridge Tuesday in Concepcion, the country's second-largest city. Bachelet said Chile has dispatched 14,000 to devestated areas.
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    Chilean army armored personnel carriers drive along a bridge Tuesday in Concepcion, the country's second-largest city. Bachelet said Chile has dispatched 14,000 to devestated areas.
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  • People wait for supplies in front of a supermarket in Concepcion.
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    People wait for supplies in front of a supermarket in Concepcion.
    Aliosha Marquez/AP
  • Police arrest a woman who was carrying goods out of a supermarket in Concepcion.
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    Police arrest a woman who was carrying goods out of a supermarket in Concepcion.
    Mario Quilodran/El Mercurio/AP
  • Rescue workers help an injured woman in Concepcion.
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    Rescue workers help an injured woman in Concepcion.
    Francesco Desgasperi/AFP/Getty Images
  • A man holds a child outside a quake-damaged building in Concepcion early on Saturday.
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    A man holds a child outside a quake-damaged building in Concepcion early on Saturday.
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  • A boat rests next to a building Monday after it was washed ashore by the tsunami in Talcahuano.
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    A boat rests next to a building Monday after it was washed ashore by the tsunami in Talcahuano.
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  • Throughout central Chile, travelers faced obstacles. Here, a collapsed bridge across the Claro river, about 112 miles south of Santiago.
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    Throughout central Chile, travelers faced obstacles. Here, a collapsed bridge across the Claro river, about 112 miles south of Santiago.
    Aliosha Marquez/AP
  • Smoke from a burning building fills the sky on the outskirts of Santiago.
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    Smoke from a burning building fills the sky on the outskirts of Santiago.
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  • Firemen search for survivors in a destroyed building in Concepcion on Sunday.
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    Firemen search for survivors in a destroyed building in Concepcion on Sunday.
    Natacha Pisarenko/AP
  • People in Concepcion stand outside guarding their homes on Monday.
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    People in Concepcion stand outside guarding their homes on Monday.
    Natacha Pisarenko/AP
  • A man holds a torn and soiled Chilean flag on Sunday in a flooded area of Pelluhue, about 200 miles southwest of Santiago.
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    A man holds a torn and soiled Chilean flag on Sunday in a flooded area of Pelluhue, about 200 miles southwest of Santiago.
    Roberto Candia/AP
  • Bejamira Neira Zapata sits in the doorway of her house Monday after the massive earthquake struck the village of Penco. The tsunami engulfed the normally placid Penco and neighboring villages.
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    Bejamira Neira Zapata sits in the doorway of her house Monday after the massive earthquake struck the village of Penco. The tsunami engulfed the normally placid Penco and neighboring villages.
    Evaristo Sa/AFP/Getty Images
  • Concepcion, about 70 miles from the epicenter, suffered some of the worst damage.
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    Concepcion, about 70 miles from the epicenter, suffered some of the worst damage.
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  • Following one of the largest earthquakes ever recorded, a woman stands in front of a destroyed home in Pelluhue.
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    Following one of the largest earthquakes ever recorded, a woman stands in front of a destroyed home in Pelluhue.
    Roberto Candia/AP

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The magnitude 8.8 quake in Chile this weekend apparently changed the length of the day — and shifted the way the Earth wobbles, according to scientists at NASA's Jet Propulsion Laboratory.

Not that anyone noticed.

Here's why scientists figure that the Earth changed the way it rotates: It turns out our planet doesn't spin like a perfect top; it actually wobbles a bit.

"The consequence of that is that the rotation pole actually moves, and it moves over the area about the size of a tennis court," says Richard O'Connell at Harvard University.

This is called the Chandler wobble. And back in the mid 1970s, O'Connell wrote a paper that showed how big earthquakes keep kicking the Earth and by so doing keep the Earth wobbling.

The Earth's Wandering, Wobbly Axis

Now we know that earthquakes aren't alone in keeping that wobble going. It's also propelled by sloshing ocean waters and by huge air masses like typhoons.

All this shifting around can also change the speed at which the Earth spins. And that of course affects the length of a day.

So how much difference can an enormous quake make? Scientists at the Jet Propulsion Laboratory figure that the shift caused by Saturday's quake in Chile should have shortened each day on Earth by about a millionth of a second. They also figure that the Earth's wobbly axis should have shifted by about 3 inches within that tennis-court-size area where it tends to wander.

But did it? It's Brian Luzum's job at the U.S. Naval Observatory to keep tabs on the Earth's rotation and orientation. And he says even the best instruments in the world can't measure a change in day length as small as a millionth of a second.

Damaged car and highway near Santiago, Chile i i

The earthquake that rocked Chile was powerful enough to damage a highway near Santiago — and even to shift the location of the Earth's rotation pole. Carlos Espinoza/AP hide caption

itoggle caption Carlos Espinoza/AP
Damaged car and highway near Santiago, Chile

The earthquake that rocked Chile was powerful enough to damage a highway near Santiago — and even to shift the location of the Earth's rotation pole.

Carlos Espinoza/AP

The Wobble Doesn't Show Up In Data

It is possible to measure the Earth's wobble pretty precisely. But considering how many things affect that wobble, it's hard to see the effect of the quake as well.

"So on a day-to-day basis, we actually will see changes on the order of 2 to 3 inches happening every day, and to try to pick out this signal in and among all the other signals, is just not really feasible," Luzum says.

The one hope was that the quake changed the wobble so abruptly that it would show up on the data.

"That's what you'd like to see to give you that eureka moment, but when we do look at the data, no such jump exists," Luzum says.

Theory says it happened, but the observations thus far aren't good enough to back that up.

Melting Ice Also Moved The Earth

But if these planetary effects are trivial on a day-to-day basis, they can really add up over geological time. Adam Maloof at Princeton University notes that ice has been melting over the past 12,000 years, as we come out of the last ice age. That's changing the Earth's orientation by about an inch, each and every year.

"You can imagine that as the ice melts you are redistributing the mass on the surface of the Earth," Maloof says. "So all this water that's caught up in the ice in poles is melting and moving into the oceans at lower latitudes."

And if you go way back in time — like to a period 800 million years ago — this kind of movement was dramatic. Over the course of a few million years, the land mass at the North Pole shifted monumentally: It slid south by 50 degrees.

"That's basically like taking Paris to the equator," Maloof says.

Nobody knows why this happened, though Maloof says one idea is that a huge volcanic plume, like the one that created the Hawaiian Islands, developed near one of the poles and that lopsided mass forced the Earth to rotate.

"It would have had major ramifications for sea level, climate, landscape, equilibrium, all sorts of effects like this," he says.

As for the effect of one quick catastrophic event: It's fair to say the Chilean quake touched hearts around the world more tangibly than it changed the spin of our planet.

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