Brigsires quaked earth

You take your hands and dig them into the earth. The Earth starts to crumble. A 30ft area, either cubed or in a circle is under the spell's effect. 

Turn 1) Dex save (Acrobatics) DC 10 + your strength score. Failed saves take 3d6 damage and fall prone, no effect on successful saves. 

Turn 2) Dex save (Acrobatics) DC 13 + your strength score. Failed saves take 5d6 damage and fall prone, no effect on successful saves. 

Turn 3) The area that was under effect rises 5 feet due to it being supported by a flaming ball. Creatures that are adjacent to the area take 2d10 damage. 

These actions start before the caster's turn, after turn three the fireball disappears and the floating area falls back into place.