I am creating an elf character and want to take the alternate racial feature that gives Fire Resistance 5. It says it is a product of the environment where the elf lived.
Are there any forests on volcanic mountains in the Golarian setting?
That variant is on the Advanced Race Guide, which is a setting neutral book (for most of it, at least). However, there are many elves who live in the deserts of Garundi and this racial trait would fit them perfectly.
Checking Giantslayer #5: Anvils of Fire, there is an article called Volcanos of Golarion, which lists many possible citizens of volcanos: Fire yai, fire giants, dragons (red, magma and underworld), obsidian gargoyles, elementals (fire and magma), magmins, mephits (fire and magma), salamanders, thoqquas, efreeti, magma oozes, flame beheaded, burning skeletons, red wyrm raveners, and finally, ghosts and wraith of victims. No elves, maybe dead elves.
Considering that the article also lists the most known volcanos, I will comment on those:
Darkmoon Wood may fit your needs, located in Northern Andoran (inner sea region).
Darkmoon Wood is located in Darkmoon Vale, at the base of Droskar's Crag, along the banks of the River Foam in northern Andoran, near the border of Isger and Druma.
and Droskar's Crag is an active volcano. Not expert enough on Golarion to know whether this would make a bad home for an elf, but Falcon's Hollow (the closest settlement, being roughly 8 miles south) has 14 elves in it's demographics (out of about 1400), so there's at least a small handful in the area.