Theory 24/Mach Number/Volcanic jets
Plume Height Is a Mach Problem
The claim
Volcanic plume height is set by the Mach number at the vent, so an eruption with a choked vent produces a different plume than one with the same mass flux but lower exit velocity.
01Mechanism
Compressibility limits the mass flux per unit area; the ratio determines whether the vent is choked and how momentum is delivered to the atmosphere.
02Prediction
Plume height should track vent Mach number.
03Refutation
Height tracking mass flux alone would remove compressibility.