Surface has two meanings in Sorcery! Sorry about that! English is tricky. Surface as a noun means 'the top layer of a site,' as in 'the surface of a site.' This is the more common usage of the word, which you can see on Buried Treasure, Teleport, or Bone Rabble. Surface as a verb means 'to move up from underwater,' as in 'surface the submerged minion.' You can see examples of this on Diluvian Kraken, Iceberg, and Mudflow. Void squares do not have a surface (or subsurface).