The panama canal uses water from the lake in the middle to fill the locks each time a ship enters and exits the canal
This uses a lot of water and the original canal locks just let the water out into the ocean.
So a drought would eventually make crossing the lake not possible.
They built new bigger locks recently that recycle the water.
But I guess they still use the old ones too.
The theory is based on seeing the change in magnetic direction of newly created rock coming from places like the mid Atlantic ridge. They can see the changes over time leading out from the center.
https://en.wikipedia.org/wiki/Geomagnetic_reversal
If you want to discredit that well. ok i guess so. I don't know what the point is.
But we do actively see magnetic north moving every year. Unless you think compasses are also fake.