There's always that volcano at the center, but if you MUST have a coastal province and magma...
Anyways, I'll keep an eye in my daily seeds for a particulary nasty site, but here's my current finds.
Title: DEC
Seed: 12162007
You'll find your "Torch of Prophets" surrounded by the Joyous Wilds of "The Luxurious Mirthful Swamps", surrounded by the Terrifying "Ocean of Jackals". As well as the central volcano, you'll find several magma vents along the shore. If you can get underneath it, there's no aquifer underneath the ocean, so there may be a place to sneak by, though the heavy forestation should enable you to go straight through.
A brief overview of the location reveals slugmen, snailmen (whoo-hoo!), skeletal sturgeon, and a living hammerhead shark, for those who want to try building a very dangerous aquarium. Can you capture and then retrieve a shark without suffocating it? Perhaps a trap with shallow water... I'm curious if land-crawling skelesharks will come hunting for your people later. That should keep things interesting.
In hindsight, one of those 'magma vents' I was talking about was simply red sand. Lets see if the others are real. Ah, there we go. The east coast features a surface level magma vent. So... fire men, undead fishies, and sharks. For extra fun, flood your fortress to 3/7 or so, and leave it open to the outside.
Now that I've found that, the image (points to southern beach, with hammerhead sharks, but the eastern one comes with the magma vent):
I'll check my daily seeds as they come up to see if I can find an island with the center being terrifying, sinister, or haunted, but so far, they've been disgustingly perky.