Repeat this mantra until it sinks in:
Light things float and heavy things sink.
It's called simple physics.
Water vapor above the atmosphere is not a liquid so the creationists belief in a water vapor canopy is not unscientific.
the upper reaches of the atmosphere contain very little water vapor because:
Light things float and heavy things sink.
The water vapor can't be "above space."
Atmospheric pressures would have helped drive this subduction from the trenches to the mid-ocean ridges if the plates crushed not slipped under the continent masses.
Atmospheric pressure does not move solid rock around like billard balls or push it down into denser rock. Why?
Because light things float and heavy things sink.
If the mantle is being sucked inward then its not only the old crust being pushed into the earth.
And what is under the mantle being "sucked in?" heavier mantle. So the crust and especially mantle cant be sucked in under heavier (denser) mantle by gravity to any overall significant degree without being reguritated back up. Why?
Because light things float and heavy things sink.
Every volcano is testimony to what happens due to subduction. It says:
Light things float and heavy things sink.
Keep repeating.
Edited by anglagard, : clarity