Sounds a lot like Mike, Lu & Og. Og would be the genius that you're thinking of. Show aired until 2001 but I'm sure reruns ran for some time after so 10 years doesn't seem too far off.
I can see OP forgetting the other two characters, or not remembering them as main characters, but that would relate to the friends that Og made. Og and Lu were actually natives of the island while Mike was a foreign exchange student who, more or less, accidentally stumbled upon this island when trying to be sent to a tropical island. If you watch the introduction of the show you'll see the volcano almost instantly. The only thing I couldn't find a direct reference for were the masks, but I don't think it's too farfetched that there were episodes were some people were wearing masks on a tropical island with tribal natives.