Here are some ideas... If you can pick up a few levels of the PrC Dweomerkeeper, you can use their Supernatural Spell ability and ignore the spell casting components of your Volcano spell (assuming it cost XP and/or gold to cast, these can be bypassed). You can also take the Alacritous Cogitation feat from Complete Mage. It allows you to leave an arcane spell slot open when preparing spells, you can use that open slot to cast any arcane spell you know of the same level or lower. Casting the spell requires a full-round action. Wow, suddenly that Volcano spell that takes 1 day to cast becomes a full-round action to cast. Not bad, eh?
If the mortals anger you, you can also use a similiar combo to wipe all of these puny mortals within a 200 mile radius by using Apocalypse from the Sky. This is a 9th level spell from BoVD (which is 3.0). You also kinda have to be evil as well, since it is an evil/corrupt spell. But here is the current combo...
Human Wizard 9/Cleric 1 (Magic Domain)/Dweomerkeeper 10
Level 1: Explosive Spell, Snowcasting, Scribe Scroll
Level 3: Energy Substitution (electricity)
Level 5: Craft Wondrous Item
Level 6: Empower Spell
Level 9: Born of the Three Thunders
Level 12: Alacritous Cogitation
Level 15: Extraordinary Spell Aim
Level 18: Arcane Thesis (Apocalypse from the Sky)
Thanks to Alacritous Cogitation, you can cast Apocalypse from the Sky with a full-round action, instead of the normal 24-hour wait. Thanks to Dweomerkeeper, you can ignore the otherwise hefty artifact requirement and any SR through Supernatural spell. Thanks to Extraordinary Spell Aim, you can exclude yourself from the nasty effects of your Explosive Empowered Energy Substituted Born of the Three Thunders Apocalypse from the Sky.
In the end, you’re doing a total of 150,480d6 (100,320d6 * 1.5) damage before any items are applied and the actual damage of the spell itself is included to anyone adjacent to you during the casting. Creatures father out take less damage depending on distance, and less than that if they hit something.
I like the Explosive metamagic feat touch of this. Not only is everything within 200 miles damaged, but because of Explosive metamagic spell feat, anything caught in that area is PUSHED to the edge of the spells' effect. And for every 10 feet they travel, they take an additional 1d6 damage. So if the inital 10d6 damage doesn't kill you, imagine being in the center of that blast and being pushed 200 MILES away from it takined 1d6 damage per 10 feet of movement. Ouch...
Anyway, since you are playing at such a high level, thought I might give you another direction you might want to take with your character.