The term is derived from volcanoes in Greece that have been dormant for years. They could erupt but choose not to right now.
Albert: I saw you and Shaneek'wa making out at the party. You do the dirty?
Taso: I got the "Greek Volcano", man...
Albert: Ouch. You go home and take care of business by yourself?
Taso: Nah, I was good, that was enough pleasure for me.
Albert: You have no game, you couldn't seal the deal, Greek Volcano
Chuck Norris is also an advocate for Greek Volcano as his pleasure taste buds are so superior to regular man that a Norris orgasm would result in too much man juice that the world could not handle (similar to the iceland volcano), which is why he's more than happy to stop before climax claiming he's received more than enough Norris pleasure.