Volcanic Flood

You cause lava to begin pouring out of the ground at a point you can see within range, creating a 1-foot thick layer of lava on the ground within a 30-foot-radius area centered on that point. The lava spreads around corners, and counts as magical difficult terrain. Any creature that starts its turn in the lava, or that moves into it, must make a Dexterity saving throw. On a failed save, a creature takes 10d6 fire damage, taking half damage on a successful save. The spell also damages objects and structures within the area, and ignites flammable objects that aren’t being worn or carried.

At the beginning of each of your turns for the duration of the spell, the radius of lava increases by 10 feet (from a 30-foot-radius to a 40-foot-radius, for example). Lava that spreads into a creature's space does not damage that creature until the beginning of its turn.

When the spell ends, any lava created by this spell disperse into a thin, black smoke.