Caused because gravity pulls air down

Gravity is the force that keeps us attracted to objects with a larger mass than us. Earth has so much mass that we are stuck to it. If we jump up, we come down. If you throw a ball up in the air, it will come down unless you throw it with such force that it escapes the pull of the earth. Many things are caused by gravity.

Ibelieve it was because of the gas act in order to preserve fuel 

Answer a mineral that contains a combination of silicon, si, and oxygen, o, is a silicate mineral. hope it ^.^