Once its axis tilts, how does the Earth “know” to return to its normal orientation? Work by Harvard researchers provides some answers.
What would happen if the Earth’s axis suddenly tilted by 50 degrees or more? It may sound like the plot of a bad science fiction movie, but scientists say it’s not an academic question — geological records clearly show such shifts have indeed happened several times throughout the planet’s history, with dramatic effects on climate and sea level.
To understand how the Earth “knows” how to return to its original orientation, Creveling and Mitrovica turned to two images, the first being the stretching of a rubber band. Jerry X. Mitrovica, professor of geophysics, and Jessica Creveling illustrate their research using a model of the Earth inside the Geological Museum at Harvard. As the planet shifts on its axis, stress on the tectonic plates that make up Earth’s crust increases, Mitrovica explained. That increased stress acts like a stretched rubber band, gradually pulling the planet back to its original rotation axis, even after millions of years of rotation at a different angle.
Previous research conducted by Mitrovica uncovered a similar phenomenon on Mars. However, while the Earth’s surface is made up of many different plates, the surface of Mars consists of a single plate. “We have shown that even with those breaks, [the Earth] still has a bit of that rubber band effect,” Mitrovica said. The second effect at work in drawing the planet back to its original orientation,
Mitrovica explained, is similar to that of a toy punching bag that bounces back up after being pushed over. Because the Earth is not a perfect sphere, when the rotation pole moves, the extra mass centered around the equator acts like an anchor, pulling the pole back to its original place. These massive shifts in the Earth’s position could have played a role in the planet’s long-term development, and life on it.