basically i wondering if with evocations your creating the element or just manipulation them in the environment? Most elements (going with the traditional earth, air, fire, water and spirit) are dont really make to much difference.

Spirit evocations are basicly using the life energies of all living things like with ki, like Ryu's Hadoken or the kamehameha from DBZ and Harry's Shield Spell.

Air is pretty evident, its all around us. Fire, if its manipulation and not creating, is igniting the oxygen in the air to create the effect.

Water i'm guessing, like Carlos's Entropy Shield, is manipulation the hydrogen and oxygen in the air to make water or using a near by source like in the Grasping Branches (animating the water in the tree).

But earth is where i'm really wondering, if you were to do a ranged attack or a block with earth, would you be tearing up the cement or pavement, kinda like in avatar the last air bender? If earth evocations work like that, it probably causes about as much collateral damage as fire and subtlety goes right out the window.

 So do evocations create the energies from nothing (which goes against every known law of the universe) or does it work more like bending for avatar? either way i doesnt matter much just looking for input on how people think it works.