1. The dust could kick up and create a "dust-screen" sort of thing that could allow to remain hidden from your opponent for a moment, and could buy you time to attack or flee, or it could kick up in your opponent's eyes, temporally blinding them and possibly doing some damage.
2. Depending on the Earth Tech there are a few different ways. For instance if its a pillar that shoots up from underneath you, then you could release the wind angled down and in front of you, so it would shoot you backwards, dodging the rising pillar. If its fissures in the ground that comes racing towards you, you could angle the wind at you feet, shooting yourself directly up in the air, dodging the fissures.