Our Shifting Poles

EVER SINCE WE STARTED constructing them, man-made dams have come with unintended consequences.

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They disturb ecosystems, negatively impact water quality, and exacerbate soil erosion—oh, and they've also altered the location of the earth’s poles.

In a study published in the journal Geophysical Research Letters, a team of scientists at Harvard University detailed their discovery that the rampant construction of dams from 1835 to 2011 has locked up so much water that the Earth’s poles have moved slightly from their axial rotation. Because Earth’s outermost layer rests upon another layer of liquid rock, a redistribution of mass on the surface—whether accomplished by glaciers during an ice age or by locking up water behind dams—can influence the orientation of the earth’s poles in a process known as “true polar wander.”