The 8.8 earthquake that struck Chile may have affected Earth’s rotation, shortening the days by as much as 1.26 microseconds, says research scientist Richard Gross at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. It is also estimated that the Earth’s figure axis has shifted 3 inches (8 cm).

Variations in the rotational speed are not uncommon, and shifts occur in both directions throughout the year. The days tend to get longer during the Northern Hemisphere’s winter months and shorter in the summer. Earthquakes and other natural disasters can affect the rotation as well. The 9.1 Sumatran earthquake in 2004, for example, shortened Earth’s days by 6.8 microseconds and shifted its axis by about 2.76 inches (7 cm).

Earthquakes shifting the Earth’s rotation may seem like a big deal, but what’s worse is the idea that man-made structures could do the same. The Three Gorges Dam in China, the one of the largest dams in the world and the largest hydroelectric power generating stations in the world, holds a total of 42 billion tons of water. The effect of raising that much water 175 ft above sea level raises Earth’s moment of inertia, thus slowing down the rotation by as much 0.06 microseconds and shift the axis by 0.8 inches (2 cm).

Yes. You read that right. The effect of moving 42 billion gallons of water 17 and a half stories up is only a quarter of the effect of this earthquake. It’s a small effect, and basically unnoticeable, but it’s still something interesting, if not dangerous. Don’t expect this to result in the 2012 apocalypse or anything.