I need a volcano!

..themed powerset/AT combination. Doesn't matter if it can solo. I actually have a very specific volcano in mind, but I think that would just wind up being a Demon Summoning/Thermal Radiation, so I'm wondering what other "volcano" sets there might be. Some combination of earth and fire is an obvious choice, but what else? And what powers specifically?

Fire / Fire melee.

Bringing the heat!

Plenty of sets could work. The only archetypes that I can think of that would have trouble with it are Defender, which lacks a Earthy/Fiery set, and Mastermind (which you said could work with Demon Summoning/Thermal).

fire/earth dom

or really an earth/ dom or troller - with customization it is easy to make it lava-like

Earth/fire dominator. Accept no substitutes.

Fire, Earth (stone), Electricity would all be solid choices.

Stone/Fire/Mu brute would work well. I also tried a Fire/Earth/Mu dominator.

Seconding Earth/Fire Dom over Fire/Earth Dom. Earth primary has the most non-sleep/confuse aoe control. /Fire secondary is the most damaging Dom secondary in the game.

Runners up:
Fire/Kin/Stone Controller: The best farmer in the game when soft-capped to smashing/lethal defense. You can run around with rock armor and hot feet for a volcanic appearance.

Stone/Fire Tank(Fire/Stone Brute) One of the best tankers in the game for a combination of taking damage and dishing it out. The Brute version is a great +3/X8 farmer for Nemesis Farm. Also Rock Armor and Brimstone Armor make a great Volcanic design when you change the color tints. (You can actually see the lava flowing on their rock armor)

I'm actually working on a Volcano toon too and for right now he's Stone/Fire Brute. I'm strongly looking at Earth/Fire and Earth/Earth Dom too. I know /Fire is best for damaging but I'm in love with that lava hammer now from playing the Brute and it'll be hard to give that up if I reroll into a Dom. But the idea of fire breath is super nice too. :P

I don't think you can go wrong with any of those.

I like my fire/earth dom. If the lava graphics on seismic smahs hitting a fire caged enemy getting burned by your lava hot feet don't give you a volcano feel, something is wrong.

*EDIT
And if fissure on lava graphics doesn't make you feel like a volcano themed toon, you may very well need help with your mental stability.

My bro-in-law has a volcano themed stone/fire tank named "Sakurajima" who's level-pacted with my mind/kin controller - they're both currently at 43.

So, yeah, I'll second the stone/tank combo. Oh, and the long beard in red with the stone skin and lava armor looks phenomenal.

I love my Earth/Fire "volcano powers" dominator. Solid control, good ranged damage, and I used the Leviathan powers of Water Spout and Hibernation to give it more of a "fury of the elements" feel to it. It's good fun.

I considered that one too. Either one is good. I went with Leviathan mainly for Water Spout (which is actually a really handy power, since it's Knockup rather than Knockback, and looks cool). Shark Skin is a bit bleh (who uses cold damage? Seriously?), but Hibernation is a good panic button.

I'm quite proud of my Volcano themed Kano Kilauea, a fire melee / shield scrapper. Shield customization allows you a nice chunk of flaming lava and fire melee has plenty of face meltingly awesome attacks. I'll try and remember to get a pic of him and post it next time I get a chance.

My Stone/Fire Tanker is called Easter Island.

You could also try using Dark somewhere in there, to represent the smoke and ash.