If a liquid is poured out of a long necked vessel it has to wait for the air to move out of its way.
If the fluid rotates with a vortex. the process goes “critical” and the water flows quickly.
If two equally dense fluids are involved, mixing takes place AFTER the venturi effect relaxes
When warm air moves away from cold air because theyare unattracive to one another in any way, the mixing reverse.
This is why the weather separates on the North Atlantic and all the other charts.
And that is how an eruption is most easily identified as having occurred.
More often than not, volcano specialist sites fail to realise that this has happened until aircraft data indicates an eruption.
