Elemental Wave

I conjure a 5ft elemental cube of force in front of me. I can choose whether it is Fire, Water, Earth, or Wind. It moves in a straight line for 15 feet before dispersing. 

Fire: Conjures a 5ft cube of fire which blasts forward, dispersing after traveling 15ft. Any creature hit by the cube or starting or ending their turn in the cube must make a Dexterity Saving Throw. On a success they take no damage, but on a failure they take 1d10+2 Fire Damage.

The fire will ignite objects on fire, however, when the spell disperses the fire will disperse as well, even if it has spread. Objects damaged by the fire will stay damaged however.

For each 2 levels above Cantrip (2, 4, 6,etc.) size goes up by 5 cubic ft and damage increases by 1d10.

Water: Conjures a 5ft cube of water which flows steadily forward, dispersing after traveling 15ft. Any creature hit by the cube or starting or ending their turn in the cube must make a Strength Saving Throw. On a success they are unmoved, but on a failure they are lifted off of the ground and moved with the cube until it disperses or travels 15ft. 

The water is drinkable however any water left behind after the spell disperses, regardless of location or situation of containment will disperse with the spell.

For each 2 levels above Cantrip (2, 4, 6,etc.) size goes up by 5 cubic ft.

Earth: Conjures a 5ft cube of rock which shoots forward, dispersing after traveling 15ft. Any creature hit by the cube must make a Dexterity Saving Throw. On a success they dodge the large brick of rock, but on a failure they take 1d8+2 bludgeoning damage and are knocked back 15ft.

If it would be cast directly on a creature such that the creature is where the spell starts, that creature must make a Dexterity Saving Throw. On a success they dodge the spell, but on a failure they are trapped inside the cube of rock until it disperses and take 2d8+2 initial crushing damage. They take an additional 1d8+2 crushing damage at the end of their turn, on which they can make a Strength Check to attempt to forcibly break free of the cube of rock.

The cube of rock has an AC of 12 and can take 15 points of damage before being destroyed.

For each 2 levels above Cantrip (2, 4, 6, etc.) size goes up by 5 cubic ft and damage goes up by 1d8 and 2d8 respectively.

Wind: Conjures a 5ft cube of wind which rushes forward, dispersing after traveling 15 feet. Any creature hit by the cube must make a Strength Saving Throw. On a success they resist the wind and are unmoved, but on a failure they take 1d4+2 bludgeoning damage and are blown back 15ft.

A draft remains behind the block of wind, slowing or accelerating creatures by 5ft of movement, respective to the direction the cube was cast.

The wind will block non-magical projectiles under 5lbs (arrows, bolts, rocks, etc.) and will move objects under 5lbs 15ft with the spell (papers, leaves, dust, insects, etc).

Gas, vapors, mist, etc will also be dispersed in a 10ft radius around the cube (15 cubic ft dispersion total).

For each 2 levels above Cantrip (2, 4, 6,etc.) size goes up by 5 cubic ft and damage goes up by 1d4. Speed affliction due to draft additionally increases by 5ft.