[yongjik]

You cannot put air at 2 km and then at 20 km high! Of course the second layer will just flow down until it's supported by the first layer, which is in turn supported by the ground. So your question doesn't really make physical sense.

[nonbel]

I agree, everything is much more complicated than your original comment implied.

[yongjik]

I... I just explained why everything adds up to what my original comment said... (sigh)