earthen blades

You touch the ground and jagged rocks jut up from the earth in areas directly in front of you in a 15ft by 40ft rectangular patch.  this is area counts as difficult terrain and any creature who start their turn on it take 2d10 bludgeoning damage and 1d6 piercing damage if they fail their saving throw or half as much on a successful one.  any creature who is in the line when this is first cast takes 4d10 bludgeoning and 2d6 piercing damage

increase the initial piercing damage by 2d6 for each level of spell slot used higher than 3rd