Quickflow Rupture

A crevice opens at a point you can see and quick-flowing lava begins to spew outward. The area starts at 5-meter radius and grows by 5 meters each round for 5 rounds. Creatures entering the lava or starting their turn in it take 2d10 Fire(3) damage. The lava is Difficult Terrain. After 5 rounds the lava develops a crust and cools - the area remains as Difficult Terrain but deals no further damage.