[thedoc (OP)]

Ryan Smith  asked the Naked Scientists:
   
This is Ryan Smith from Los Angeles. Love the podcast.

I was curious how the tides have changed over the Earth's history. I imagine the moon was much closer to the Earth and moving much faster millions or billions of years ago. How did this effect the frequency and magnitude of the tides? How in turn could this have effected erosion and weather?

Thank you for your time.

Ryan Smith
   
What do you think?

[chris]

Yes, indeed. As the moon migrates away from the Earth (by acquiring energy from the torque applied by the fact that it slightly lags the tidal bulge it induces on the moonward side of the Earth) so the gravitational effect that drives the tides is mitigated and so the tidal amplitude falls. There is geological evidence (going back many millions of years) for much higher tides in the past, when the moon was closer.