re: Reprisal: Earth as seen from Mars (MGS)
There's a fascinating article written by some of my heroes of science, commenting on how Aliens (e.g. Martians) might have been able to interpret plate tectonics on Earth by remote sensing. It's a big PDF - Here.
It also serves a great debunk of any Expanding Earthers or Creationists you meet who suggest that the evidence for Plate Tectonics is not firm, or somehow questionable.