As altitude rises, air pressure drops. ... As altitude increases, the amount of gas molecules in the air decreases—the air becomes less dense than air nearer to sea level. This is what meteorologists and mountaineers mean by "thin air." Thin air exerts less pressure than air at a lower altitude.
Lines of Parallel, like the lines of latitude and longitude, if you need to remember which is what then remember that lat is flat So latitude is the horsontal one
