The Siberian Traps refer to a volcanic event which occurred some 250 million years. Essentially, all of Siberia erupted. Over a period of thousands of years, Maybe tens of thousands and maybe even hundreds of thousands of years. Anyway, this event exists at the permian triassic boundary and is likely a leading cause of the mass die offs which occurred at this time (again, over hundreds of thousands of years).
There are also the Deccan traps (India) and Emeishan traps (china).
This would be a cool setting idea.
Sorta of a Doom set in the Middle Ages