As I understand it, this is exactly what makes a volcanoe erupt.
Not exactly, as I'm given to understand it. In the case of many
volcanos it is an actual phase change that occurs to increase the
volume of the propelling gas, a more dramatic effect. Water boils
as the molten material rises to lower pressures. The feedback is
certainly there, however; this is a runaway phenomenon.
Another related natural phenomenon is the turnover of lakes such
as the one which occurred a few years ago in Africa. Colder water
at great depth in a lake was apparently saturated with CO2 when it
started to rise for some reason. As it rose carbon dioxide came
out of solution, further decreasing the density and creating a
runaway. When a large volume of this water reached the surface it
gave off so much carbon dioxide gas that it asphyxiated thousands
of people who lived in the lake's basin or valley. CO2, being
denser than air, simply sat there like a lake for long enough to
do the damage.
Another related phenomenon is thought to occur when hydrated
methane rises from the depths of the sea to produce bubbling sea
water too low in density to bouy up the unlucky vessel that
happens to be in the wrong place at that time.
Nature manifests these and related phenomena in several different
ways, all the time. Are these things not sufficiently interesting
that they might replace "Bernoulli lift" and "entropy as disorder"
in the curricula we pass on to our students?
I'm certainly glad that I was not constrained by silly curriculum
requirements in the raising of my own children.