Hello, I ask for your help because I can't find any information about earth crust-atmosphere phase transition. I noticed indeed that our feet tread upon a solid surface, while our nostrils breath a gazeous compound ! This remark seems so obvious that I can't find any description neither analysis about this phase transition. If we look under our feet, there is no problem, we can find the moho' discontinuity at 35km, the gutenberg discontinuity at 2885km, etc... Same if we look over us, there is the tropopause at 11km, then the stratopause, etc... But it is impossible for me to find any schema or study including earth mantel AND atmosphere. Why the hell is the 0 km discontinuity located at 0 km? Which statistic model let us understand it? This lack of back standing about our self-environnement make me feel like the human being is still the center of the universe like 500 years ago... (I mean if the human being was born in a solid/ductile part of the earth mantle like termites or whatever the "surface" of our world would had been at -10 km or any other value) I am mostly looking for the mathematic explanation of the phenomenon (explanation of the localization (height) and cause of earth crust-atmosphere phase transition) Thank you for your lightnings. PS . I am not physician.