An evil sorceror has cast a spell on the moon. Over the course of two years, it will seemingly disappear.
It will disappear from the surface inwards. Anything touching the surface shall be treated as part of the surface. This excludes light.
This occurs in the medieval period, so no pesky moon landings or anything.
What effect does this have on the earth, and the people living on it?
Obviously, diminished tides and stuff. But would there be seismic activity? Deaths? Extinctions? At what point do things really start changing?
EDIT: The timescale happens over a lot longer scale, so any changes would be far less drastic. Medieval technology would shape the effect on humanity a little more than the question the 'duplicate' is linking to.