![has the earth shifted on its axis has the earth shifted on its axis](https://www.space.fm/astronomy/images/diagrams/seasons-large.gif)
"Changes in Earth's spin and the orientation of Earth's axes affect signals we get from the satellites in Earth orbit." "Using a global network of GPS receivers, we can monitor the rotation of Earth with high precision," he says. "We haven't actually measured the shift," says Gross. So far, however, it's all calculation and speculation. It was a truly seismic shift-no pun intended. 27, 2010, the Chilean quake may have moved the figure axis as much in a matter of minutes as it normally moves in a whole year. The rebounding process is still underway and so the figure axis naturally moves. This unloaded the crust and mantle of the Earth, allowing the planet to relax or "rebound" back into a more spherical shape. On its own, the figure axis moves about 10 centimeters per year as a result of "Ice Age rebound." After the last great glacial period some 11,000 years ago, many heavy ice sheets disappeared. "The Chilean quake shifted enough material to change the mass balance of our entire planet," Gross says.Ī shifting figure axis is nothing new. The figure axis is Earth's axis of mass balance, and the spin axis wobbles around it. As a result of these asymmetries, Earth slowly wobbles as it spins. There's more land in the north, more water in the south, a great ocean in the west, and so on. Continents and oceans are distributed unevenly around the planet. "The figure axis defines not how Earth is tilted, but rather how it is balanced," says Gross.Įarth is not a perfect sphere.
![has the earth shifted on its axis has the earth shifted on its axis](http://www.space.fm/astronomy/images/animations/anim_seasons1.gif)
But that's not how the "figure axis" works. If the Earth tilted over 3 inches, you probably think you would have noticed. "According to our calculations, the quake moved Earth's figure axis by about 3 inches (8 cm)," says geophysicist Richard Gross of the Jet Propulsion Laboratory in Pasadena, California.