1 (Fire) 1 (Mountain) For each (Fire) (Mountain) you have, 1 Damage to 1 Town/City.
The elemental threshold is only 1 fire and 1 mountain, but is it for each PAIR of Fire and Mountain you deal one damage? Or does simply meeting the elemental threshold (1 fire, 1 mountain) mean you are doing 2 points of damage? If you had 4 fire and 4 mountain, is that 8 damage to 1 Town/City, or is it "only" 4 damage?
I searched the FAQ for the ability and didn't see an answer, but I recall at some other point seeing information pointing to that it's each individual element of either type that gives 1 Damage, so that by having 1 Fire and 1 Mountain, you would deal 2 Damage.