Goroma Volcano can be active for 1-5 days. It's very random.
The best to see if it's active or not is to listen NPC Towncryer in Thais.
Towncryer: Hear ye! Hear ye! The volcano on Goroma is spitting fire. Creatures are spawning, strong and dire. Lava is heading up the land. Adventurer, be careful or it will be your last stand!
You can also check World Board in Adventurer's Guild:
The volcano on Goroma sends his fiery message into the sky. A lot of creatures are flooding the lands together with its lava.