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NASA has calculated that the Three Gorges Dam in China dam slows the Earth's rotation by 0.06 microseconds (reference https://www.kinetica.co.uk/2014/03/27/chinese-dam-slows-down-earths-rotation/).

Has extracting oil and mining changed the Earth's rotational speed?

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    $\begingroup$ "NASA" did not calculate this. One person who works for NASA calculated this. NASA tries not to stifle unconventional views as those unconventional views can at least some of the time lead to breakthroughs. Note well: The calculated change in the Earth's rotation rate has not been observed for two simple reasons. One is that that small of a change is unobservable. The other is that there are a lot of observable changes in the Earth's rotation rate that are multiple orders of magnitude larger. The Earth is not as good of a clock as once thought. $\endgroup$ Commented Jan 28, 2023 at 21:40

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The capacity of the Three Gorges Dam is 39.3 km3, or 39.3 × 109 m3. One cubic meter of water has a mass of 1 tonne, so the capacity of the dam is 39.3 billion tonnes of water (billion as recognized in the USA). From here onward I use billion as it is used in the USA, 1 followed by nine zeros (109).

The Three Gorges Dam is situated in one small location, relatively speaking. Mine production occurs at various locations around the world, so there will be a countering affect because of this.

Considering the mining aspect, the two main commodities that are mined in bulk quantities are iron ore and coal. The total world annual production of iron ore is 2.5 billion tonnes. The total annual amount of coal mined is 7.7416 billion tonnes.

Combined with iron ore production, that amounts to 10.2416 billion tonnes of iron ore and coal in one year. This is 26 percent the capacity of the Three Gorges Dam.

The total amount of crude oil produced in the world in 2021 was 77,043,680 barrels per day, which is 28.1396 billion barrels, or 4.476 billion cubic meters for that year. Taking a density for crude oil as 900 kg/m3 (0.9 t/m3), this equates to 4.0284 billion tonnes of crude oil.

Add this to the amounts for iron ore and coal and the total is 14.27 billion tonnes extracted in one year. This amounts to 36.3 percent of the capacity of the Three Gorges Dam.

As mentioned previously, the Three Gorges Dam is located in relatively small area of the world. Mine and oil extraction occurs around the planet. There will be an effect from such mining and oil extraction activities, but the effect will be much less.

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