# Did the Three Gorges Dam shift the North Pole by 2 cm?

Numerous sources repeat that, apart from slowing down the rotation of the globe, the Three Gorges Dam caused the geographic pole to shift by 2 cm. For example: https://blog.prv-engineering.co.uk/engineering-three-gorges-dam/ "The secret behind this phenomenon is called inertia and occurs as a result of Newton’s First Law Of Motion. According to NASA scientist, a shift in mass that size does affect the Earth. Raising 42 billion tons of water 180 meters above sea level increases the Earth’s moment of inertia which slows its rotation. It increases the length of a day by 0.06 microseconds while shifting the pole position by about 2 cm (0.8 inch). I'm curious, how did they calculated above mentioned "2cm"?,

• "Raising 42 billion tons of water 180 meters above sea level increases the Earth’s moment of inertia which slows its rotation." The 180 meters is insignificant. You are taking a layer of water from the oceans and moving it to a certain latitude, which means a certain distance from the Earth's axis, which varies by thousands of km depending on the latitude. I did the math on the length-of-day change here. Dec 29, 2020 at 4:32
• Tectonic subsidence can counteract the raised water and changing sea level, so its only theory unless we have precise metrics of the planets geometry, which we don't afaik. Meanwhile a 315 billion-tonne iceberg breaks off Antarctica in 2019. Jan 27, 2021 at 4:46
• – uhoh
Jan 27, 2021 at 22:43
• The NASA source: jpl.nasa.gov/news/nasa-details-earthquake-effects-on-the-earth This seems to be based on this paper: semanticscholar.org/paper/… (click the academic.oup.com link). Feb 5, 2021 at 5:16