Resurface . A resurfaced Underground Detonation is removed from the game after it resolves.
Explained
Destroy a base.801.9c
Choose a base on board when you deploy it, either player's. It goes to its owner's scrapyard. If it has left the board by the time this resolves, nothing happens (801.9c).
Resurface . A resurfaced Underground Detonation is removed from the game after it resolves.802.3d
While it is in your scrapyard, you may deploy it from there for this cost instead of its own, whenever you could deploy it from your hand. It goes into the crossfire, and the opponent may react. Deployed from your hand, it goes to the scrapyard as usual, so it can be used again this way.