Widen Spell
You can cast your spells so that they occupy a larger space.
Benefit: You can alter a burst, emanation, or spread-shaped spell to increase its area. Any numeric measurements of the spell’s area increase by 100%. A widened spell uses up a spell slot three levels higher than the spell’s actual level.
Spells that do not have an area of one of these four sorts are not affected by this feat.
Source: Pathfinder Core Rulebook, p. 137