When the skies release a column of fire, the land around becomes a barren place...
Can such phenomenon be explained with some rare, but "closely possible" circumstances? I don't think about lightnings/meteors here, rather about something lasting a bit longer (at least some hours). I thought about several things like a combustion of stacked flammable gas pushed out by pressure changes or describing an abnormal activity related to higher parts of the atmosphere, but all that still sounds too abstract to me.
Of course there is no need to take the sky part literally, it'd just look alike.
I don't mind including some magic if it's necessary, but you know, it's all about not making things too boring. :P