How does gravity relate to a stream's ability to erode and deposit materials

Gravity pulls down the water, without gravity water would just be floating in the air. Gravity is the reason water continues to flow into streams, and the reason water flows along streams to rivers and lakes. Since it the motion of water along, over, and through things that causes them to erode, gravity is the force driving erosion. Gravity is erosion's engine. Gravity is one of the forces shaping sedimentation

The earths atmosphere is made up of nitrogen and oxygensolids turning into gases is called sublimation.