Which gas in earth’s atmosphere forms ozone? oxygen nitrogen water vapor carbon dioxide which characteristics describe the troposphere? check all that apply. is the innermost layer contains the ozone layer has the highest air pressure spans 12–50 km above earth is a good place for planes to fly which gas in earth’s atmosphere has increased over time due to burning fossil fuels? oxygen nitrogen water vapor carbon dioxide which phrases describe air density? check all that apply. increases as altitude increases equals mass divided by volume pushes molecules in one direction exerts more pressure as it increases measures how tightly molecules are packed