# Does the geographic North Pole move?

The magnetic North (or South) Pole moves due to activities in the inner of Earth. And earthquakes can tilt the Earth's orientation a tiny bit. But can and does the axis' orientation relative to the surface change too? A major impact could surely do it, but could the Earth's inner activities?

I don't mean precession, nor tectonics or continental drift, but the movement of the rotation axis. Could for example the geographic North Pole move to Greenland? (Not Greenland moving to the NP)

• Do you mean precession? link one link two – Gimelist Mar 25 '16 at 9:48
• @Michael No, I don't mean precession. Precession means that the entire Earth changes its tilt. The geographic North Pole remains in the same geographical place. I will try to clarify. – LocalFluff Mar 25 '16 at 10:17
• @LocalFluff: Except that thanks to plate tectonics, that "same geographical place" moves about - which means that not only was the North Pole not always in the middle of the Arctic Ocean, there wasn't always an Arctic Ocean. – jamesqf Mar 25 '16 at 17:55

Yes, it's called polar motion.

The rotational pole moves continuously, as you can see from the right-hand side of this figure (below) by the Earth Orientation Centre (EOC) and the International Earth Rotation and Reference Systems Service (IERS). The figure shows about 650 days of time; mjd is modified Julian day and time goes along the locus in the polar motion diagram.

The left-hand side of the figure shows Length of Day, and I think that's chiefly why they are making these refined polar measurements — to keep track of leap seconds, etc.

It's been established, by Fong et al. (19996), among others, that earthquakes could change the earth's rotational axis, by redistributing mass on a large scale. Their table 1 shows [the sort of effect that individual earthquakes theoretically have — edited after comment from David Hammen] on the length of day; $\Psi$ is the excitation vector:

The EOC's website lists other geophysical excitations, among them:

• Atmospheric angular momentum
• Oceanic angular momentum
• Hydrological excitation function
• Axial angular momentum of the core

### References

Chao, Benjamin Fong, Richard S. Gross, Yan-Ben Han (1996). Seismic excitation of the polar motion, 1977–1993. Pure and Applied Geophysics, September 1996, Volume 146, Issue 3, pp 407-419. DOI 10.1007/BF00874727