17 October 2012
Convection in a dirty dish
Posted by Callan Bentley
Saw this in a greasy / soapy baking pan in my kitchen sink the other day:
Do you see those lobe-shaped light areas, separated by dark septae? I think that’s the semi-gelled signature of gravitational instability, perhaps thermally driven. I’m speaking of convection: upwelling in the round light areas, and sinking of denser material in the dark seams in between.
A closer look at the structure of the suspension, and an annotated interpretation…
Convection is a really important process in Earth systems – from the formation of hurricanes to the driving force behind (beneath?) plate tectonics. You can get insights into mantle dynamics if you just avoid doing the dishes. Even if it’s not driven by heat differences – the presence of greasy micro-droplets may be the culprit here, there is still an analogy with Earth systems – it’s like looking at soft sediment deformation (ball & pillow, flame structures) in a sedimentary density inversion.
So density is important in explaining “vacuum” and the creation of measureble density, old news – worth repeating but still old old news (Descarte).