Earth Explosion

A bolt of crackling energy blasts from your closed fist holding the ball of clay to point you can see within range and then earth at that point explodes upwards hurling burning stones skyward. Each creature in a 30 foot square must make a Dexterity saving throw. A target takes 4d6 bludgeoning damage and 3d6 fire damage on a failed save and half as much damage on a successful one. 

The area is now difficult terrain and the spell must target earth or stone. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd. (for both bludgeoning and fire damage)