you throw  a big boulder . Each creature in a 10-foot cube originating up to 10 ft away  must make a strength  saving throw. On a failed save, a creature takes 1d8 blungeiong  damage and is pushed 10 feet away from you. On a successful save, the creature takes half as much damage and isn't pushed. as long as you are concentrating you can make more rocks and reapeat 

you create one sqaure of difficulft terain next to the boulder 

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 for each slot level above 2nd.