How do we determine how much the surface of the Earth deflects due to tidal forces from the Moon (and Sun)?

  • $\begingroup$ a good place to start: is here $\endgroup$
    – Jim
    May 16, 2014 at 14:25
  • $\begingroup$ Are you asking how much the surface moves, or how we measure how much it moves? $\endgroup$ May 16, 2014 at 15:24
  • $\begingroup$ I've read that it moves about 1/100 of how much tide water moves. I have no idea if that is correct, so I guess I am asking both. $\endgroup$
    – Shookster
    May 16, 2014 at 16:44

1 Answer 1


The Wikipedia article on Earth tides includes a table showing how much the crust moves in response to the tidal forces from the Moon. The maximum movement is a shade under 40cm, though more typical would be 10 - 20cm. Ocean tides can be up to 10m, though 4m would be a more reasonable value, so the movement of the crust is about one tenth that of the sea rather than one hundredth.

I'm afraid I don't know how such small movements in the crust are measured. I assume some form of surveying is used.


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